studies on the synthesis of anti-inflammatory drug...
TRANSCRIPT
Chapter I
HO
HO
O
NN
NH
O
HO
O
Studies on the synthesis of
anti-inflammatory drug,
Balsalazide
INTRODUCTION:
Ulcerative colitis is a common inflammatory disease of the colon and rectum which has an
estimated annual incidence of 0.002 to 0.006% (2 to 6 per 100 000 people) in the US.[1]
The
clinical symptoms of ulcerative colitis are bloody diarrhea, stool urgency, tenesmus and
abdominal discomfort; these events tend to wax and wane with time. The modern history for the
treatment of diarrhea, intestinal inflammation / infection begins with the development of several
oral rehydration agents, intestinal anti-infectives, adsorbents, antipropulsives (opioids),
intestinal anti-inflammatory agents, antidiarrheal micro-organisms and antidiarrheals which are
summarized in Table-1.1.
Ulcerative colitis is classified as mild, moderate or severe on the basis of clinical and
endoscopic findings. Salicylates, in either oral or topical formulation, are the drugs of first
choice for obtaining remission or maintenance of remission in patients with mild to moderate
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 2
Chapter - I
disease. Topical, oral or intravenous glucocorticoids, mercaptopurine, azathioprine and surgical
resection are reserved for patients affected with more severe forms of the disease.[1]
Table-1.1
Rehydration Oral rehydration therapy
Intestinal anti-
infectives
Antibiotics (Neomycin, Nystatin, Natamycin, Streptomycin, Polymyxin
B, Paromomycin, Amphotericin B, Kanamycin, Vancomycin, Colistin,
Rifaximin)
Sulfonamides (Phthalylsulfathiazole, Sulfaguanidine,
Succinylsulfathiazole)
Nitrofuran (Nifuroxazide, Nifurzide)
Imidazole (Miconazole)
Arsenical (Acetarsol)
Oxyquinoline (Broxyquinoline)
Intestinal
adsorbents
Charcoal, Bismuth, Pectin, Kaolin, Crospovidone, Attapulgite,
Diosmectite
Antipropulsives
(opioids)
Opium Tincture (Laudanum), Codeine, Morphine, Camphorated Opium
Tincture (Paregoric)
Crosses BBB (Diphenoxylate (Diphenoxylate/atropine), Difenoxin)
Does not cross BBB (Loperamide)
Intestinal anti-
inflammatory
agents
Corticosteroids acting locally (Prednisolone, Hydrocortisone,
Prednisone, Betamethasone, Tixocortol, Budesonide, Beclometasone)
Antiallergic agents, excluding corticosteroids (Cromoglicic acid)
Aminosalicylic acid and similar agents (Sulfasalazine, Mesalazine,
Olsalazine, Balsalazide, Ipsalazide)
Antidiarrheal
micro-organisms
Saccharomyces boulardii
Other
antidiarrheals
Albumin tannate, Ceratonia, Octreotide, Racecadotril
5-aminosalicylic acid (5-ASA), also known as mesalazine is an anti-inflammatory drug used to
treat inflammatory bowel disease, such as ulcerative colitis[2]
and mild-to-moderate Crohn's
disease.[3-5]
Mesalazine is a bowel-specific aminosalicylate drug that acts locally in the gut and
has its predominant actions there, thereby having few systemic side effects.[6]
As a derivative
of salicylic acid, mesalazine (2) is also thought to be an antioxidant that traps free radicals,
which are potentially damaging byproducts of metabolism.[7]
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 3
Chapter - I
Table-1.2
Sr.
no.
Generic name
Systematic (IUPAC) name
Structure
1 Mesalazine (2)
5-amino-2-hydroxybenzoic acid
HO
O
HONH2
2 Sulfasalazine (3)
2-hydroxy-5-[(E)-2-{4-[(pyridin-2-
yl)sulfamoyl]phenyl}diazen-1-
yl]benzoic acid
HO
O
HON
N
SNH
O
O
N
3 Olsalazine (4)
5-[(2Z)-2-(3-carboxy-4-oxocyclo-
hexa-2,5-dien-1-ylidene)hydrazino]-
2-hydroxybenzoic acid
HO
O
HONH
N
O
OH
O
4 Ipsalazide (5)
(E)-5-((4-(((carboxymethyl)amino)-
carbonyl)phenyl)azo)-2-hydroxy
Benzoic acid
HO
O
HON
N
O
HN
O
OH
5 Balsalazide (1)
(E)-5-([4-(2-
carboxyethylcarbamoyl)phenyl]diaze
nyl)-2-hydroxybenzoic acid
HO
O
HON
N
O
HN
O
OH
Aminosalicylic acid and similar agents, which were approved by United States food and drug
administration (USFDA) and available in the market are given in Table-1.2.
Balsalazide is the generic name of 5-[(1E)-[4-[[(2-carboxyethyl)amino]carbonyl]phenyl]azo] 2-
hydroxy- benzoic acid (1). It is an oral prodrug of 5-ASA (2), having an inert carrier molecule,
N-(4-aminobenzoyl)β-alanine (4-ABBA, 8).[8]
After oral administration, 1 is split into 2 and 8
via azo-reduction by the colonic micro flora.[9]
2 is then acts directly on the colon to reduce the
local inflammation of the colonic mucosa, responsible for the symptoms of ulcerative colitis.[10-
12] Balsalazide (1) appeared to be an effective treatment option when compared to Salazopyrin
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 4
Chapter - I
(3). The clinical use and dosage of 3 are limited by adverse reactions,[13-15]
several of which are
attributed to the absorption of the carrier metabolite sulphapyridine.[16]
Balsalazide (1) is an therapeutic agent for ulcerative colitis. It is used as disodium dehydrate
salt. It’s molecular formula is C17H13N3O6Na2.2H2O and molecular weight is 437.32amu. The
commonly used dose of balsalazide is 6.75g per day, which is equivalent to 2.3g of mesalamine
(2).[17]
REVIEW OF LITERATURE:
Balsalazide disodium and its complete synthesis was first disclosed by Chan[18]
in 1983,
assigned to Biorex Laboratories Limited, England, claiming product ‘Balsalazide’ and process
of its preparation. The synthesis involves converting 4-nitrobenzoyl chloride (6) to 4-
nitrobenzoyl-β-alanine (7), hydrogenating with Pd/C (5%) in ethanol and isolating by adding
diethyl ether to produce 4-aminobenzoyl-β-alanine (8). Thereafter, 4-aminobenzoyl-β-alanine
(8) was treated with hydrochloric acid and sodium nitrite to generate N-(4-diazoniumbenzoyl)-
β-alanine hydrochloride salt (9) which was reacted at low temperature with disodium salicylate
to furnish Balsalazide disodium insitu which was added to dilute hydrochloric acid at low
temperature to produce Balsalazide (1) (Scheme-1.1). Thus obtained Balsalazide was
recrystallized with hot ethanol and converted to pharmaceutically acceptable salt (disodium
salt).
H2N
O
NH
O
NH
NN
HO
O
HO
O
HO
HO
O
HO
HO
O
NN
NH
O
HO
O
O2N
Cl
O
O2N
O
NHHO
O
.Cl
Beta alanine
water / NaOH
methanol
Pd/C, H2
water, Con. HCl
Aq. NaNO2 solution
water
NaOH, Na2CO3
(6) (7) (8)
(9)(10)(1)
.....Scheme-1.1
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 5
Chapter - I
Optimization of this diazonium salt based process was performed by Huijun et al[19]
and
reported the preparation of the title compound in 64.6% overall yield. Zhenhau et al[20]
have
synthesized 1 from 4-nitrobenzoic acid (12) via chlorination, condensation, hydrogenation,
diazotization, coupling and salt formation with overall yield 73%. Li et al[21]
have given product
in 73.9% total yield starting from 4-nitrobenzoyl chloride (6), where as Yuzhu et al[22]
confirmed chemical structure of Balsalazide disodium by elemental analysis, UV, IR, 1H-NMR
and ESI-MS etc. Shaojie et al[23]
have also followed same process for its preparation. Yujie et
al[24]
synthesized 1 in this way; preparation of 4-nitrobenzoyl-β-alanine (7) under microwave
irradiation of 420 W at 52oC for 10sec., reduction in ethyl acetate in the presence of Pd/C
catalyst then diazotization, coupling and salt formation.
Eckardt et al[25]
have developed a process for the preparation of Balsalazide which comprises,
conversion of 4-aminobenzoyl-β-alanine (8) to 4-ammoniumbenzoyl-β-alanine sulfonate salt
using a sulfonic acid in water. This was treated with aq. sodium nitrite solution at low
temperature to generate 4-diazoniumbenzoyl-β-alanine sulfonate salt (11) which was quenched
with aq. disodium salicylate to furnish Balsalazide disodium solution. This was further acidified
to allow isolation of 1 and then conversion to disodium salt (Scheme-1.2) in 76% yield.
H2N
O
NH
O
NH
NN
HO
O
HO
O
HO
HO
O
HO
HO
O
NN
NH
O
HO
O
water, MSA
Aq. NaNO2 solution
water
NaOH, Na2CO3
.MSA
(8) (11)(10)
(1)
.....Scheme-1.2
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 6
Chapter - I
PRESENT WORK:
Present work uncovered a new synthetic process to prepare Balsalazide disodium consisting no
isolation of any intermediate which is cost effective, safe and industrially feasible. Hence, we
have developed and optimized new process, impurities formed in the process were identified,
prepared and characterized. A new process is developed for the preparation of Balsalazide (1)
and analogs starting from salicylic acid. Further, we have prepared different analogs, positional
isomers and metabolites.
RESULTS AND DISCUSSION:
Four synthetic approaches are described herein, among which approach A deals with 3-steps
preparation of Balsalazide in water. Process development and identification of impurities also
included in this approach. Approach B discloses almost twenty analogs of Balsalazide
preparation without isolation of any intermediate (in situ). Approach C depicted synthesis of
Balsalazide and analogs in four consecutive steps starting with salicylic acid and Approach D
uncovered reactions due to isomers of nitro benzoic acids and hydroxy benzoic acids.
APPROACH A:
The present investigation is directed towards an improved process to prepare Balsalazide
disodium (Scheme-1.3), by reacting 4-nitrobenzoic acid (12) with an halogenating agent[26-32]
selected from thionyl chloride, oxalyl chloride in an organic solvent such as toluene, diisopropyl
ether, cyclohexane or methylene chloride, to give 4-nitrobenzoyl chloride (6), which insitu was
reacted with sodium salt of β-alanine in water to give 4-nitrobenzoyl-β-alanine (7). The ESI
mass spectrum of 7 [(M-H)-] was observed at m/z 237 in negative ion mode, which suggested
the molecular weight of 7 was 238. IR stretching at 3379cm-1
indicates NH stretching of amide.
The 1HNMR spectrum of compound 7, in (DMSO-d6), β-alanine corresponding chemical shifts
at δ 2.54 ppm and δ 3.48 ppm were appeared. Similarly, shift at δ 8.89 ppm in 1HNMR
corresponds to amide of 7 observed. The assigned structure for compound 7 hence clearly
confirmed the above spectral data.
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 7
Chapter - I
4-nitrobenzoyl-β-alanine (7) was suspended in water in the presence of a base and hydrogenated
using palladium on carbon, and thereafter treated with an acid to give 4-aminobenzoyl-β-alanine
(8). The base was selected from sodium hydroxide, sodium carbonate, sodium bicarbonate,
potassium hydroxide or aqueous ammonia and acid was selected from hydrochloric acid,
sulfuric acid or acetic acid. The ESI mass spectrum of 8 [(M-H)-] was observed at m/z 207.3,
suggests the molecular weight of 8 was 208. IR stretching at 3418, 3334 and 3241cm-1
indicate
NH and NH2 stretching. In 1HNMR spectrum of compound 8, corresponding chemical shift of
NH2 at δ 5.60 ppm observed. Thus assigned structure for compound 8 was clearly confirmed by
the above spectral data.
4-aminobenzoyl-β-alanine (8) was treated with hydrochloric acid and sodium nitrite to generate
N-(4-diazoniumbenzoyl)-β-alanine hydrochloride salt (9) and treated with disodium salicylate to
furnish Balsalazide disodium. This was acidified with an acid to pH 4.2-5.0 and stirred at 50-
80oC, more preferably at 60-65
oC for four hours to give a mixture of Balsalazide (1) and its
monosodium salt [60:40 to 80:20]. The ESI mass spectrum of 1 as [(M-H)-]displayed peaks at
m/z 356.1, indicates the mass of the product was 357. IR stretching at 3371, 3039 indicates NH
and OH stretching. In 1HNMR spectrum of compound 1, chemical shifts corresponds to
salicylic acid at δ 6.95 ppm, δ 7.95 ppm and δ 8.34 ppm were observed. The assigned structure
for compound 1 was clearly confirmed by the above spectral data.
Thus obtained product was treated with sodium carbonate in water and disodium salt was
precipitated with alcohol, more preferably isopropyl alcohol at 5-35oC to obtain
pharmaceutically accepted salt (disodium salt).
The Balsalazide and its monosodium salt mixture obtained was purified using aqueous 1,4-
dioxane to yield highly pure Balsalazide acid and its monosodium salt mixture that was ideal for
the preparation of disodium salt. Purification occurs when 1,4-dioxane suspension was heated at
high temperature at 90-95oC and filtered at relatively high temperature 60-65
oC. Several
impurities go into solution by heating at 90-95oC. Structures of these impurities were given in
Figure-1.1.
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 8
Chapter - I
H2N
O
NH
O
NH
NN
HO
O
HO
O
HO
HO
O
HO
HO
O
NN
NH
O
HO
O
O2N
OH
O
O2N
O
NHHO
O
.Cl
Beta alanine
water / NaOH
water / NaOH
Pd/C, H2
water, Con. HCl
Aq. NaNO2 solution
water
NaOH, Na2CO3
SOCl2 / IPE
(12) (7) (8)
(9)(10)(1)
.....Scheme-1.3
PROCESS DEVELOPMENT AND IMPURITY PROFILE:
For the preparation of N-(4-nitrobenzoyl)-β-alanine (7), 4-nitrobenzoic acid (12) was selected as
a starting material because of its easy commercial availability and it was also well known in
chemical literature that acid group can be converted to amide conveniently via chloride
formation. Further, preparation of acid chloride has been described in literature, wherein acid
has been reacted with thionyl chloride[26]
/ oxalyl chloride[27]
/ phosphorous pentachloride[28]
/
phosphorous trichloride[29]
/ phosphorous oxychloride[30]
/ triphosgene[31]
etc[32]
to obtain acid
chloride, which on reaction with amines provides amides. We intended to prepare acid chloride
but owing to handling advantages decided to take it in situ for further conversion into amide.
Thus, 4-nitrobenzoic acid (12) was reacted with thionyl chloride in presence of DMF (catalyst)
in different solvents and after completion of reaction, isolated product, 4-nitrobenzoyl chloride
(6) was added to sodium salt of β-alanine. Results of the some batches are summarized in
Table-1.3.
It was clear from the above experiments that major impurity formed in above reaction was 4-
nitrobenzoic acid (12), which was forming due to decomposition of 4-nitrobenzoyl chloride (6)
with water. Subsequent to this observation, we tried to minimize the exposure of 6 to water.
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 9
Chapter - I
Figure-1.1
HO
HO
O
NN
OH
O
N
O
NHO
HN OH
O
N
HO
HO
O
HO
O
NN
NH
O
HO
O
OHN
N
NH
O
HO
O
HO
NN
NH
O
HO
O
HO
O
HO
NN
HNO
O
OH
NN
NH
O
HO
O
HO
O
HO
HNO
OH
O
NN
NH
O
HO
O
HO
N
N
HN
O
OH
O
NN
NH
O
HO
O
HO
N
N
HN OH
O
O
NH
OH
O O
(13) (14)
(15) (16)
(17) (18)
(19) (20)
Table-1.3
Solvent Thionyl
chloride
HPLC purity of
(6)
HPLC purity of
(7)
Impurity
formed (12)
Toluene 1.75 m. eq. 89.58% 84.87% 9.68%
n-Heptane 1.25 m. eq. 99.28% 95.89% 4.02%
Cyclohexane 1.25 m. eq. 99.86% 93.30% 6.62%
Cyclohexane 1.25 m. eq. 99.57% 93.47% 6.22%
Cyclohexane 1.25 m. eq. 99.46% 92.10% 7.69%
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 10
Chapter - I
Therefore, after formation of 4-nitrobenzoyl chloride (6), instead of isolation, it was reacted
with sodium salt of β-alanine. Results of some experiments are summarized in Table-1.4.
Table-1.4
Solvent Thionyl chloride HPLC purity of (7) Impurity formed
(12)
Methylene chloride 1.20 m. eq. 92.12% 7.59%
Toluene 1.20 m. eq. 95.87% 3.45%
Tetrahydrofuran 1.25 m. eq. 85.53% 13.40%
Tetrahydrofuran 1.25 m. eq. 88.07% 10.46%
1,4-Dioxane 1.25 m. eq. 85.69% 13.59%
Diisopropyl ether 1.25 m. eq. 99.48% 0.29%
Diisopropyl ether 1.25 m. eq. 99.15% 0.68%
Diisopropyl ether 1.10 m. eq. 99.52% 0.35%
Diisopropyl ether 1.10 m. eq. 99.51% 0.43%
However, 4-nitrobenzoic acid (12) mostly gets eliminated during filtration into mother liquor in
presence of diisopropyl ether. In one experiment, after reaction, diisopropyl ether layer was
separated first and then adjusted pH. The presence of 12 was observed more in 7.
It is known that 4-nitrobenzoic acid (12) would convert in to Des-β-alanine Balsalazide (13) and
may contaminate the final product. Therefore to fix a limit of 12 in 7 some experiments were
carried out to know its impact in product i.e., Balsalazide (1). Results of some experiments are
summarized in Table-1.5.
Table-1.5
(12) in (7) (27) in (8) (13) in (1)
1.38% 0.18% 0.07%
1.08% 0.07% Not detected
0.80% 0.08% Not detected
0.75% 0.07% Not detected
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 11
Chapter - I
Other impurity which forms in preparation of 7 at ~0.5% level was confirmed by LCMS as N-
(2-(3-hydroxypropylcarbamoyl)ethyl)-4-nitrobenzamide (21), does not have any adverse impact
on the final product quality. This impurity was eliminated during the isolation of 8 in the
reduction stage, which remains in the mother liquor owing to its higher solubility in water.
O2N
O
NHO
HN OH
O (21)
Formation of 7 was studied by varying the temperature and it was observed that slow addition
of 6 to sodium salt of β-alanine at < 10oC maintaining pH > 8 gave the best results. By these
conditions, we could obtain 7 close to 98% of chromatographic purity.
In the next step, which is well known in the chemical literature that nitro group can be
converted to amino by catalytic hydrogenation.[33]
Hydrogenation is a facile reaction, which is
carried by reacting 7 with hydrogen in presence of palladium on carbon. This reaction we tried
in different solvents at 25-35oC with varying quantities of palladium on carbon and at different
hydrogen pressure, which are summarized in Table-1.6.
Table-1.6
Solvent Pd/C (w/w) Hydrogen pressure
Kg/cm2
Impurity A
(27)
Impurity B
(26)
Impurity C
(25)
Ethanol 4% 4 0.50% 0.31% 0.27%
Ethanol 5% 5 0.25% 0.58% 0.75%
Methanol 3% 5 0.05% 0.12% Not detected
Methanol 2% 10 0.08% 2.02% 0.21%
Based on the above data, we concluded that impurities were found in all experimental
conditions. We analyzed the sample, 8 by LCMS and found the related substances / side
reaction were formed exactly as reported in the literature (Figure-1.2).[34]
One experiment was
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 12
Chapter - I
carried out using ethanol as a solvent and added BHT (anti-oxidant) in reaction itself. The result
was similar as of the above.
Figure-1.2
O
HN OH
O
NN
O
NHHO
O
O
O
NHHO
O
O2N
O
NHHO
O
ON
O
NHHO
O
HOHN
O
NHHO
O
H2N
O
HN OH
O
NN
O
NHHO
O
O
HN OH
O
NH
HN
O
NHHO
O
(7)
(22)
(23)
(8)
(24)
(25)
(26)
Some experiments were carried out using methanol and modified the product isolation by using
anti solvents, which has no significant impact on product quality. The purification study was
also not encouraging to get the quality product.
We explored alternatives to hydrogenate 7 in less volume of solvent and conditions, where these
impurities may form in minimum amount. For that water was used as a solvent. As 7 was almost
insoluble in water, one mole equivalent of base was used to dissolve it as its sodium salt in
water and hydrogenated using Pd/C at 30-45oC. The reaction mass was filtered and after
removal of catalyst one mole equivalent of acid was added to precipitate the 8. Details of some
experiments are summarized in Table-1.7.
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 13
Chapter - I
Table-1.7
Solvent /
Volume
Pd/C
(w/w)
Hydrogen
Pressure
(Kg/cm2)
Time Impurity
A (27)
Impurity
B (26)
Impurity
C (25)
Water / 14 4% 15-20 30 min 0.06% ND ND
Water / 5 2% 18-22 1 hr 0.79% ND ND
Water / 5 2% 15-20 2 hr 2.75% 0.48% ND
Water / 5 2% 20-30 30 min ND 0.08% ND
Water / 5 2% 20-30 2 hr 30 min 0.05% ND ND
The advantages of hydrogenation reaction in water are:
(1) Higher purity and conversion of product and less formation of impurities,
(2) Less volume of reaction mass hence high throughput,
(3) Environment friendly,
(4) High productivity,
(5) Cost effective,
(6) Inherent safety where solvents are used and recovery are avoided.
The impurities except 27, formed in hydrogenation step were not capable of forming
hydrochloride salt, therefore these can be removed by filtration of 4-ABBA hydrochloride in
next step.
It is also well known that azo compounds are prepared by interaction of diazonium salt with a
phenol in the presence of sodium hydroxide or with an amine in the presence of sodium acetate.
The coupling is an electrophilic substitution reaction wherein diazonium ion reacts at the
position of greatest electron availability i.e., the position of ortho or para to the electron
releasing phenoxy or amino group (Figure-1.3).
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 14
Chapter - I
Figure-1.3
HO
N O2O
NO
NO
+-H2O
H2N
O
NHHO
O
slow
N
O
NHHO
O
NO H
H
-NO2
-H+
N
O
NHHO
O
NO
H
N
O
NHHO
O
HON
H+
tautomerization
N
O
NHHO
O
N
(8)
Keeping the like sequence we prepared the diazonium salt of 8 and added to disodium salt of
salicylic acid (10) using water as a solvent. 10 was used in 1.02 m. eq. with respect to 8 and
found conversion to product only 94% by HPLC. In another experiment with 1.0 m. eq. of
salicylic acid (10), product formation was reduced to only 86%. Upon increasing the mole ratio
to 1.2, product formation was ~97%, which was decreased again (93%) when 1.5 m. eq. of
salicylic acid (10) was used. Based on above observation optimization of coupling reaction has
been done with 1.2 m. eq. of 10.
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 15
Chapter - I
HO
HO
O
NN
OH
O
N
O
NHO
HN OH
O
N
HO
HO
O
HO
O
NN
NH
O
HO
O
OH
NN
NH
O
HO
O
HO
NN
NH
O
HO
O
HO
O
HO
NN
HNO
O
OH
NN
NH
O
HO
O
HO
O
HO
HNO
OH
O
NN
NH
O
HO
O
HO
N
N
HN
O
OH
O
NN
NH
O
HO
O
HO
N
N
HN OH
O
O
NH
OH
O O
O2N
Cl
O
O2N
OH
O
O2N
NH
O
HO
O
O2N
O
NHO
HN OH
O
H2N
OH
O
H2N
NH
O
HO
O
H2N
O
NHO
HN OH
O
NN
NH
O
HO
O
O
HN
O
OH
NN
NH
O
HO
O
O
HN
O
OH
NH
HN
NH
O
HO
O
O
HN
O
OH
O
N
OH
O
N
NH
O
HO
O
N
O
NHO
HN OH
O
N
NN
Cl
Cl
Cl
NN
NH
O
HO
O
HO
HO
O
H2N OH
O
PNB
COUPLING
HYDROGINATION
Pd-C / H2
Pd-C / H2Pd-C
/ H 2
DIA
ZO
CO
UP
LIN
G
NaNO2 / HCl NaNO2 / HCl NaNO2 / HCl
HO
HO
O
HO
HO
O
HO
HO
O
NaOH / Na2CO3
NaOH / Na2CO3
NaOH / Na2CO3
BALSALAZIDE PROCESS
HO
HO
O
NaOH / Na2CO3
DE
CA
RB
OX
YL
AT
ION
GOMBERG-BACHMANN
COUPLING
N
NH
O
HO
O
N
Cl
N
NH
O
HO
O
N
Cl
DECARBOXYLATION
GOMBERG-BACHMANN
COUPLING
N
NH
O
HO
O
N
Cl
.....Scheme-1.4
Analysis of Balsalazide (1) sample by LCMS found some unknown impurities. The presence of
impurities in an Active Pharmaceutical Ingredient (API) can have a significant impact on the
quality and safety of the drug products. Therefore, it was necessary to study the impurity profile
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 16
Chapter - I
of the API to be used in the manufacturing of a drug product. International Conference on
Harmonization (ICH) guidelines recommends identification and characterization of all
impurities which were present in API in a level of ≥0.05% (based on daily dose).[35]
In this
context, we have undertaken a comprehensive study to synthesize and characterize the
impurities in Balsalazide API (Scheme-1.4).
These impurities were: 5-[[4-[carboxy]phenyl]azo]-2-hydroxybenzoic acid (Des-β-alanine
Balsalazide, 13); 5-[4-[2-(2-carboxyethyl carbamoyl)ethyl carbamoyl]phenyl azo]-2-hydroxy-
benzoic acid (Balsalazide β-alanine, 14); 3-[[4-[[(2-carboxyethyl)amino]carbonyl]phenyl]-azo]-
2-hydroxybenzoic acid (Balsalazide 3-isomer, 15); 3-[4-(4-hydroxy phenylazo)benzoylamino]-
propionic acid (Decarboxy Balsalazide, 16); 2,4-bis-[[4-[(2-carboxyethyl)amino]carbonyl]-
phenyl]azo salicylic acid (Bis-azo salicylic acid, 17); 5-[2-[4’,5-bis[(2-
carboxyethyl)carbamoyl]-biphenyl-2-yl]diazenyl]-2-hydroxybenzoic acid (Biphenyl-azo
salicylic acid, 18); 3-[4-[5-[4-(2-carboxy ethyl carbamoyl)phenylazo]-2-hydroxy
phenylazo]benzoyl amino]propionic acid (Bis azo diacid, 19); 2,4-bis[[4[[(2-
carboxyethyl)amino]carbonyl]phenyl]azo]-3-[4-[[(2-carboxyethyl)-amino]-
carbonyl]phenyl]phenol (Bis-azo triacid, 20). In addition to these we have also synthesized and
characterized two metabolites[36]
namely 3-(4-acetylamino benzoylamino)-propionic acid (N-
acetyl-8) and 5-acetylamino 2-hydroxybenzoic acid (N-acetyl-2).
Des-β-alanine Balsalazide 13, a carryover impurity, originates due to the presence of 4-
nitrobenzoic acid 12 in intermediate 7 of the Balsalazide process. This impurity may also form
due to the amide hydrolysis of Balsalazide during the process. Des-β-alanine Balsalazide (13)
was prepared starting with 4-nitrobenzoic acid 12 according to the following scheme (Scheme-
1.5). Catalytic hydrogenation of 12 with Pd/C in methanol yielded 27, which was diazotized
with sodium nitrite in aqueous hydrochloride and coupled with sodium salicylate to give the
desired compound 13 in excellent yield. The ESI mass spectrum of 13 displayed peaks at m/z
285.2 [(M-H)+] in negative ion mode and as sodium ion adduct at m/z 307.0 [(M-H)+Na]. In
positive ion mode this compound appeared at m/z 287.2 [(M+H)+] in the mass spectrum. In
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 17
Chapter - I
1HNMR spectrum of compound 13, corresponding peaks of β-alanine at δ 2.61 ppm and δ 3.56
ppm were absent. Similarly in 13
CNMR spectrum peaks at δ 34.6 ppm and δ 36.6ppm due to β-
alanine moiety were also not observed. The assigned structure for compound 13 is clearly
confirmed by the above spectral data.
HO
HO
O
HO
HO
O
NN
OH
O
O2N
Oa b c
(10)
OH
H2N
O
OH
O
OH
NN
(12) (27) (28)
(13)
.Cl
Reagents and conditions: (a) Methanol, Pd/C, H2, RT, 2-3 h, 98%; (b) Water, conc. HCl , 0-5°C then aq. NaNO2
solution, 0-5°C, 1 h, ~100%;(c) Water , NaOH / Na2CO3, Salicylic acid, 0-5°C then addition of diazonium salt 28
solution, 1 h, ~100%.
.....Scheme-1.5
Like Des-β-alanine Balsalazide 13, Balsalazide β-alanine 14 originates from N-(4-
nitrobenzoyl)di-β-alanine 21, which may present in intermediate 7 and carry through the
synthetic process to give this impurity in Balsalazide finish product.
Balsalazide β-alanine 14 was prepared by hydrogenating N-(4-nitrobenzoyl)di-β-alanine 21
with Pd/C in methanol to give the corresponding amine 29 ,which on diazotization followed by
coupling with salicylic acid in alkaline medium results the desired compound 14 (Scheme-1.6).
The ESI mass spectrum of 14 displayed peaks at m/z 427.2 [(M-H)-] and as sodium ion adduct at
m/z 449.0 [(M-H)-+Na] in -ve ion mode; in +ve ion mode this impurity appeared at m/z 429.2
[(M+H)+]. The
1H and
13C NMR spectra of compound 14 also support the assigned structure for
14 (Di-β-alanine analog of Balsalazide).
Balsalazide 3-isomer 15 is a positional isomer of Balsalazide 1 and can form due to the coupling
of diazonium salt 9 to 3-position of salicylic acid 10 instead of 5-position (Scheme-1.7).
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 18
Chapter - I
N-(4-Aminobenzoyl)-β-alanine 8 as hydrochloride salt was diazotized with aqueous sodium
nitrite solution at 0-5°C and further treated with sodium salicylate in water/ isopropyl alcohol
mixture at 0-5°C to yield compound 15 as a byproduct along with 1. The ESI mass spectrum of
compound 15 was showing equal mass value as that of Balsalazide. The 1H-NMR of 15 exhibits
three doublet of doublets at δ 6.61 ppm (dd, J = 7.7 Hz, 1H), 7.57 ppm (dd, J = 8.0 Hz and 1.7
Hz, 1H), and 7.87 ppm (dd, J = 8.0 Hz and 1.7 Hz, 1H) corresponding to three hydrogen at 4, 5
and 6 position of aromatic ring of salicylic acid. 13
C-NMR data also confirmed the assigned
structure of compound 15.
O2N
O
NHO
HN OH
O
H2N
O
NHO
HN OH
O
N
O
NHO
HN OH
O
N
N
O
NHO
HN OH
O
N
HO
HO
O
HO
HO
O
c
(10)
(21) (29) (30)
(14)
ba
Cl
Reagents and conditions: (a) Methanol, Pd/C, H2, RT, 2-3 h, 98%; (b) Water, Conc. HCl, 0-5°C aq. NaNO2
solution, 0-5°C, 1 h, 100%; (c) Water, NaOH /Na2CO3, Salicylic acid, 0-5°C then addition of diazonium salt 30
solution, 1 h, 82%.
.....Scheme-1.6
O
NH
NN
HO
O
(9)
(10)
HO
O
NN
NH
O
HO
O
(15)
OH
H2N
O
NHHO
O
(8)
a b
Cl
Reagents and condition: (a) Water, conc. HCl, 0-5°C aq. NaNO2 solution, 0-5°C, 1 h, ~100%; (b) Water, NaOH /
Na2CO3, Salicylic acid, 0-5°C then addition of diazonium salt 9 solution, 1 h, ~7%.
.....Scheme-1.7
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 19
Chapter - I
Decarboxy Balsalazide 16 was detected in 1 as a degradation product. Decarboxylation of
Balsalazide would result in this impurity. We have prepared this impurity from 4-
hydroxybenzoic acid 31, wherein N-(4-aminobenzoyl) β-alanine 8 was diazotized with aqueous
sodium nitrite solution / hydrochloric acid at 0-5°C and added to aqueous alkaline solution of 31
to obtain compound 16 (Scheme-1.8). The ESI mass spectrum of compound 16 displayed peak
at m/z 312.1 [(M-H)-] in -ve ion mode, which was 44 mass unit (amu) less than Balsalazide
(m/z356.2). In +ve ion mode its base peak appeared at m/z 314.0 [(MH) +
] and peak
corresponding to sodium ion adduct appeared at m/z 336.0 [(MH)+Na]. The 1H-NMR spectrum
of this compound showed signals at δ 6.97 (d, J = 8.8 Hz, 2H), 7.84 (d, J = 8.8 Hz, 2H), 7.88 (d,
J = 8.8 Hz, 2H), and 8.04 (d, J = 8.8 Hz, 2H), these values indicates that both aromatic rings are
para-substituted in addition 13
CNMR and DEPT spectra are also supporting the assigned
structure for compound in the structure, 116.1(CH), 121.9(CH), 125.2(CH), 128.4(CH).
O
NH
NN
HO
O
HO
(9) (31)
NN
NH
O
HO
O(16)
H2N
O
NHHO
O
(8)
a b
O
OH
HO
Cl
Reagents and conditions: (a) Water, conc. HCl, 0-5°C aq. NaNO2 solution, 0-5°C, 1 h, 100%; (b) Water, NaOH /
Na2CO3, salicylic acid, 0-5°c then addition of solution of diazonium salt 9, 1 h, 91%.
.....Scheme-1.8
Bis-azo salicylic acid 17 formed due to the coupling of Diazo intermediate 9 with Balsalazide 1
on ortho-position with respect to phenolic –OH group during its preparation, and carry through
the process to give this impurity in Balsalazide. The synthetic sequence for the preparation of
this impurity is depicted in Scheme-1.9. Using half mole of salicylic acid in diazo coupling
reaction yielded this impurity. But due to number of side reactions, formation of 17 was less.
The ESI mass spectrum of impurity 17 displayed peak at m/z 577.2 [(MH)+], 221 mass unit
(amu) more than Balsalazide (m/z 356.2) indicating attachment of Diazo intermediate 9 to
Balsalazide. The signals in 1H-NMR spectrum of this impurity at δ 7.90 (2d, J = 8.8 Hz, 4H)
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 20
Chapter - I
and 8.01 (2d, J = 8.8 Hz, 4H) represents two Diazo intermediate moieties, the remaining two
aromatic peaks at δ 8.15 (d, J = 2.5 Hz, 1H) and 8.51 (d, J = 2.5 Hz, 1H) due to benzene ring of
salicylic acid. The smaller coupling constant value (J = 2.5 Hz) indicates the meta-coupling in
the benzene ring, which authenticates the assigned structure for compound 17.
Base-promoted free radical coupling (Gomberg-Bachmann reaction)[37-39]
between the aryl
diazonium salt 9 and Balsalazide lead to the formation of Biphenyl-azo salicylic acid 18. The
synthetic sequence to prepare this impurity is illustrated in Scheme-1.9. Using half mole of
salicylic acid in reaction yielded this impurity. The formation of 18 was very less as there were
various side reactions. ESI mass spectrum of impurity 18 displayed peak at m/z 549.2 [(MH)+],
28 mass unit (amu) less than Bis-azo salicylic acid 17, indicating Diazo group detachment from
Bis-azo salicylic acid 17. 1HNMR data for compound 18 are 6.70 (d, J = 8.8 Hz, 1H), 7.58 (d, J
= 8.5 Hz, 2H), 7.60 (dd, J = 8.8 Hz and 2.5 Hz, 1H), 7.70 (d, J = 8.8 Hz, 1H), 7.93 (d, J = 8.5
Hz, 2H), 7.97 (dd, J = 8.8 Hz and 1.4 Hz, 1H), 8.05 (d, J = 1.4 Hz, 1H), 8.17 (d, J = 2.5 Hz,
1H).
O
NH
NN
HO
O
(9)
(10)
NN
NH
O
HO
O
H2N
O
NHHO
O
(8)
a b
HO
O
HO
NN
HNO
O
OH
NN
NH
O
HO
O
HO
O
HO
(17)
(18)
HNO
OH
O
Cl
Reagents and conditions: (a) Water, conc. HCl, 0-5°C aq. NaNO2 solution, 0-5°C, 1h, ~100%; (b) Water, NaOH /
Na2CO3, 0.5 mole eq. Salicylic acid, 0-5°C then addition of solution of 9, 1 h, 3-7%.
.....Scheme-1.9
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 21
Chapter - I
Bis-azo diacid 19 originates due to decarboxylation of the compound 17 and contaminate the
product. Bis-azo triacid 20 originates due to Gomberg-Bachmann type coupling of 9 and 19
(Scheme-1.10). The compound 19 was prepared by reacting diazonium salt 9 with alkaline
solution of para-hydroxybenzoic acid 31 (0.5 mole equivalent), whereas the compound 20 was
obtained by reacting 9 with alkaline solution of 0.25 mole equivalent of 31.
O
NH
NN
HO
O
(9)
(31)
NN
NH
O
HO
OH2N
O
NHHO
O
(8)
a b
HO
NN
NH
O
HO
O
HO
N
N
(19)
(20)
N
N
HN
O
OH
O
HN OH
O
O
NH
OH
O O
Cl
Reagents and conditions: (a) Water, conc. HCl, 0-5°C, aq. NaOH solution, 0-5°C, 1 h, ~100%; (b) Water, NaOH
/Na2CO3, 0.5 (for 19) / 0.25 (for 20) mole eq. 4-hydroxy benzoic acid 31, 0-5°C, solution of 9, 1 h, 19 (~32%) and
20 (~36%).
.....Scheme-1.10
Balsalazide disodium is freely soluble in water. After completion of the reaction, the mass was
acidified to different pH and filtered small sample at different temperature as Balsalazide (1).
Result of some experiments are summarized in Table-1.8.
Table-1.8
pH of
reaction
mass
Filtration
Temp
(oC)
Balsalazide-3-
isomer (15)
Bisazo
salicylic acid
(17)
Bis-azo
diacid
(19)
Bis-azo
triacid
(20)
HPLC
purity
0.5 2-5 0.43 0.21 0.16 0.16 96.53
0.5 2-5 0.39 0.19 0.17 0.21 97.26
2.0 2-5 0.44 0.33 0.17 0.26 96.18
2.0 25-30 0.42 0.09 0.11 0.10 98.40
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 22
Chapter - I
Isolation of Balsalazide by filtration was very slow and taken plenty of time. Due to poor
filterability, Balsalazide was extracted in organic solvents at lower pH and recrystallized from
the same solvent. Results of some experiments are summarized in Table-1.9.
Table-1.9
Solvent Balsalazide-3-
isomer (15)
Bisazo
salicylic acid
(17)
Bis-azo
diacid (19)
Bis-azo
triacid (20)
HPLC
purity
Ethyl acetate 0.24 0.16 0.16 0.15 97.25
Ethyl acetate 0.33 0.05 0.13 0.14 98.07
Methyl ethyl
ketone
0.31 0.06 0.24 0.11 99.07
Methyl ethyl
ketone
0.22 0.07 0.19 0.18 98.68
It was observed from above experimental results that during extraction / recrystallization
Balsalazide-3-isomer (15) was decreasing in both ethyl acetate and methyl ethyl ketone,
whereas Bisazo salicylic acid (17) was decreasing only in ethyl acetate while remained almost
same in ethyl methyl ketone. Bis-azo diacid (19) and Bis-azo triacid (20) impurities were not
decreasing much in both the solvents. Requirement of high volume and higher temperature were
major drawbacks for use of both the solvents owing to lower solubility of Balsalazide in these
solvents. This process suffered from disadvantages such as use of large volume of solvents, it's
recovery and adverse cost impact and compromised safety. Moreover, the yield was also low.
Therefore to resolve this problem, the reaction mass was acidified to pH 4.2-5.0 and stirred at
50-80oC. Isolated a mixture of Balsalazide and its monosodium salt at 25-45
oC (sodium content
~3.54%, by ion chromatography).
This process improved not only filterability but also purity. Most of the impurities had also
reduced to reasonable levels. See Table-1.10.
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 23
Chapter - I
Table-1.10
pH of
the
reaction
mass
Filtration
temp.
(oC)
HPLC
Purity
Balsala
zide-3-
isomer
(15)
Bis-
azo
triacid
(20)
Bis-
azo
diacid
(19)
Des-β-
alanine
Balsalazi
de (13)
Bisazo
salicyl
ic acid
(17)
Yield
(w/w)
4.0 25-30 97.97 0.25 0.28 0.14 0.15 0.19 1.63
4.1 25-30 99.22 0.08 0.14 0.17 0.16 ND 1.56
4.2 25-30 99.58 ND 0.05 0.11 ND ND 1.45
4.2 40-45 99.34 0.05 0.10 0.13 0.05 0.05 1.27
4.5 40-45 99.46 0.06 0.06 0.15 0.07 0.07 1.46
4.5 40-45 99.58 0.04 0.03 0.12 ND 0.06 1.35
From the above table, we concluded that pH ~4.2 of the reaction mass and the filtration
temperature (25-35oC) was suitable for our process. Under these conditions most of the
impurities decreased and product quality as well as yield increased. In the case of pH (4.5) and
filtration temperature (40-50oC), results are same as that of above but decrease in yield was
noted. Yield was less due to pH as well as temperature owing to high solubility of Balsalazide at
particular pH (4.5) as it was in the form of a mixture of Balsalazide and its monosodium salt.
To know the behavior of these impurities in the final product, we converted Balsalazide (1)
having above impurities into Balsalazide disodium. 3-[4-[5-[4-(2-carboxy ethyl
carbamoyl)phenylazo]-2-hydroxy phenylazo]benzoyl amino]propionic acid (Bis azo diacid, 19);
2,4-bis[[4[[(2-carboxyethyl)amino]carbonyl]phenyl]azo]-3-[4-[[(2-carboxyethyl)-amino]-
carbonyl]phenyl]phenol (Bis-azo triacid, 20); 2,4-bis-[[4-[(2-carboxyethyl)amino]carbonyl]-
phenyl]azo salicylic acid (Bis-azo salicylic acid, 17) and 5-[[4-[carboxy]phenyl]azo]-2-
hydroxybenzoic acid (Des-β-alanine Balsalazide, 13) did not eliminate in mother liquor, hence
contaminating the product. So it was necessary to purify the product in this stage only. Different
solvents were tried to attain the good quality of Balsalazide. Results of some purification
attempts are summarized in Table-1.11. Values given in brackets are Input quantities.
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 24
Chapter - I
Table-1.11
Solvents Balsala
zide-3-
isomer
(15)
Bis-
azo
triacid
(20)
Bis-azo
diacid
(19)
Des-β-
alanine
Balsalazide
(13)
Bisazo
salicylic
acid
(17)
HPLC
purity
Aq. Ethanol (1:1) 0.03
(0.20)
0.13
(0.13)
0.21
(0.19)
ND
(ND)
ND
(0.06)
99.04
(99.36)
Aq. Methanol (20%
w/v)
0.08
(0.20)
0.13
(0.13)
0.20
(0.19)
0.12
(ND)
0.06
(0.06)
99.37
(99.36)
Aq. n-propanol (1:1) 0.06
(0.20)
0.12
(0.13)
0.22
(0.19)
ND
(ND)
0.05
(0.06)
99.47
(99.36)
Aq. THF (1:1) 0.03
(0.14)
0.07
(0.20)
0.22
(0.20)
ND
(ND)
0.03
(0.05)
99.65
(99.41)
Aq. Acetone (10%
w/w)
ND
-
0.32
(0.30)
0.16
(0.21)
1.01
(1.98)
ND
(ND)
98.32
(97.37)
Aq. acetic acid
(10%w/w)
0.05
(0.20)
0.16
(0.14)
0.16
(0.50)
ND
(ND)
0.22
(0.17)
99.09
(97.15)
Aq. acetic acid
(10%w/w)
0.12
(0.28)
0.11
(0.10)
0.17
(0.18)
ND
(ND)
0.08
(0.07)
99.42
(98.65)
Aq. DMF 0.43
(0.58)
0.72
(0.81)
0.14
(1.13)
0.74
(ND)
ND
(0.07)
97.50
(97.72)
Aq. ACN (10% w/v) 0.06
(0.58)
0.11
(0.81)
0.19
(0.13)
ND
(ND)
ND
(0.07)
99.55
(97.92)
Aq. 1,4-dioxane (10%
w/v)
0.21
(0.31)
0.14
(0.13)
0.19
(0.17)
0.05
(0.09)
0.05
(0.07)
98.97
(98.27)
Aq. 1,4-dioxane (5%
w/v)
0.16
(0.31)
0.07
(0.13)
0.11
(0.17)
ND
(0.09)
0.05
(0.07)
99.24
(98.27)
Aq. 1,4-dioxane (5%
w/v)
0.12
(0.31)
0.06
(0.13)
0.09
(0.17)
ND
(0.09)
0.05
(0.07)
99.24
(98.27)
DMF / Toluene 0.05
(0.05)
0.17
(0.17)
0.20
(0.16)
0.21
(0.27)
0.06
(0.22)
99.09
(98.78)
Acetonitrile, Water
(1:1)
0.17
(0.70)
0.05
(0.07)
0.16
(0.15)
ND
(ND)
ND
(ND)
99.25
(95.03)
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 25
Chapter - I
According to above study, 1,4-dioxane was slightly a better solvent to remove all impurities in
Balsalazide and its monosodium salt mixture. So based on above conclusion, we optimized the
purification in Aq. 1,4-dioxane (50%w/v) and the experimental results are summarized in
Table-1.12.
Table-1.12
Balsalazide-
3-isomer
(15)
Bis-azo
triacid
(20)
Bis-azo
diacid
(19)
Des-β-
alanine
Balsalazide
(13)
Bisazo
salicylic
acid
(17)
Highest
Unknown
HPLC
purity
Yield
(w/w)
ND
(0.06)
ND
(0.10)
0.01
(0.16)
0.06
(0.24)
0.04
(0.07)
ND
(0.29)
99.89
(98.91)
0.80
ND
(0.30)
ND
(0.05)
ND
(0.15)
ND
(0.05)
0.05
(0.06)
0.05
(0.10)
99.90
(99.30)
0.80
0.03
(0.48)
0.01
(0.12)
0.03
(0.19)
0.04
(0.15)
0.07
(0.11)
0.06
(0.14)
99.75
(98.53)
0.77
ND
(0.05)
ND
(0.04)
0.02
(0.23)
ND
(ND)
0.03
(0.07)
0.03
(0.08)
99.92
(99.39)
0.77
From the above tabulated results, we have concluded that Balsalazide purification was
necessary to remove all the impurities in this stage. The yield by the above purification method
is also higher compared to earlier purification method.
In next step, Balsalazide and its monosodium salt mixture was converted to disodium salt by
using sodium hydroxide, sodium carbonate or sodium bicarbonate etc.
Our aim was to achieve the maximum yield with good product quality using the mild condition
i.e., low temperature and mild base (sodium carbonate) for the preparation of Balsalazide
disodium. Therefore, Balsalazide and its monosodium salt mixture was taken in water pH was
adjusted to neutral (6.5) using aq. sodium carbonate to prepare a clear solution. The obtained
solution was filtered to remove any insoluble and isopropyl alcohol was added to the filtrate to
precipitate the product. The obtained yield was 1.15w/w. In this modified and optimized
process, extra impurity formation was not observed.
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 26
Chapter - I
APPROACH B:
Approach B discloses almost twenty analogs of Balsalazide preparation without isolation of any
intermediate (in situ). The synthetic process is same as of Approach A which directs towards a
green and improved process to prepare Balsalazide disodium and its analogs in situ three steps
in aqueous condition. It starts by reacting 4-nitrobenzoic acid (12) with an halogenating agent
such as thionyl chloride, in an organic solvent such as diisopropyl ether, to give 4-nitrobenzoyl
chloride (6), which in situ is reacted with sodium salts of various amino acids, selected from α,
β and γ amino acids (40[a-t], Figure-1.4) in water to give 4-nitrobenzoyl-amino acid sodium
salt (7[a-t]),. After completion of reaction, biphasic reaction mass was separated, and the lower
aq. layer, containing 4-nitrobenzoyl-amino acid sodium salt is hydrogenated using palladium on
carbon, to give 4-aminobenzoyl-amino acid sodium salt (8[a-t]), Scheme-1.11.
Amino acids
(40[a-t])
O2N
O
AA
H2N
O
AA
N
O
AA
N
.Cl
HO
HO
O
NN
O
AAHO
HO
O
O2N
OH
O
water / NaOH
Pd/C, H2
water, Con. HCl
Aq. NaNO2 solution
water
NaOH, Na2CO3
SOCl2 / IPE
O2N
O
Cl
water / NaOH
(12) (6) (7[a-t])
(8[a-t]) (9[a-t])
(10)
(1[a-t])
.....Scheme-1.11
Thus obtained, 4-aminobenzoyl-amino acid was treated with hydrochloric acid and sodium
nitrite to generate N-(4-diazoniumbenzoyl)-amino acid hydrochloride salt (9[a-t]) and treated
with disodium salicylate to furnish Balsalazide disodium and its analogs (1[a-t]).
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 27
Chapter - I
This is acidified with an acid to pH 4.2-5.0 and stirred at 50-80oC, more preferably at 60-65
oC
for four hours to give a mixture of Balsalazide and its monosodium salt. Thus obtained product
is treated with sodium carbonate in water and disodium salt was precipitated with alcohol, more
preferably isopropyl alcohol at 5-35oC to obtain pharmaceutically accepted salt (disodium salt).
Figure-1.4 (40[a-t])
H2N
O OH
H2N
O OH
H2N
O OH
H2N
O OH
H2N
O OH
H2N
O OH
SH
H2N
O OHO
OH H2N
O OHO
NH2
H2N
O OH
OHH2N
O OH
Cl
H2N
O OH
NH O
OH
NH O
OH
HO
H2N
O OH
O
OH H2N OH
O
H2N
O
OHH2N
O
OH
H
H2N
O
OH
H
H2N
O
OH
H
H2N
O
OH
H
a b cd e
f g h i
j k l m
n o p q
r s t
The detailed experimental procedure with analytical data of all analogs are given in
experimental section.
APPROACH C:
Balsalazide and its analogs (1[a-t]) consisting four steps and starting from salicylic acid (10)
were prepared. The history starts with the conversion of salicylic acid (10) to its methyl ester
(32) using thionyl chloride with catalytic amount of DMF in methanol as a solvent. 4-
aminobenzoic acid (27) is treated with hydrochloric acid and sodium nitrite to generate an
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 28
Chapter - I
diazonium salt and treated with methyl salicylate (32) as obtained above to furnish an
intermediate (33, a key raw material in this approach) as shown in Scheme-1.12.
HO
HO
O
HO
O
O
Methanol
SOCl2
(10) (32)
H2N
O
OH
water, Con. HCl
Aq. NaNO2 solution
HO
O
O
NN
O
OH
(33)
(27)
.....Scheme-1.12
For the formation of peptide bond in the next stage, we treated 33 with methyl esters of different
amino acids (40[a-t]) using following strategies;
1) hydroxy group protection with acetic anhydride,
2) acid acivation with thionyl chloride,
3) acid activation with chloroformates,
4) acid activation with sulfonyl chlorides, and
5) using carbodiimides, as peptide coupling agent.
The results of these reactions are summarized schematically in Scheme-1.13.
It is clear from reaction Scheme-1.13 that, reaction is going to complete only by carbodiimide
reagents, without formation of any major impurity / by product.
Reaction of 33 with acetic anhydride under reflux gives impurity 35. Proton NMR of the
isolated product showing mixture of products 34 and 35 i.e., chemical shift observed at δ 2.35
ppm (s, 3H, COCH3), δ 3.88 ppm (s, 3H, OCH3) and δ 2.44 ppm (s, 1.6H, COCH3). This 1.6H
corresponds to impurity 35. Mass also conformed formation of di-acetylated impurity with mass
value is m/z 385, more 42 mass value than m/z 343 in positive ion mode [M+H]+. In -ve mode
it's showing m/z 341 as [M-H]- for 34.
Reaction of 33 with thionyl chloride in toluene under reflux condition with catalytic amount of
DMF confirms conversion to acid chloride 36 by TLC. This is reacted with methyl ester of
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 29
Chapter - I
amino acid salt (40o) with base to yield product 37 as a gummy mass with lots of impurities (as
monitored by TLC).
In another approach, 33 is activated with phenyl chloroformate and then reacted with methyl
ester of amino acid salts (40o). Analytical data supports the formation of product 37 with mass
value m/z 386 as [M+H]+, as well as impurity 38 with mass value was m/z 506. In
1H NMR
spectrum (DMSO-d6) the chemical shift observed are not clear due to mixture of products.
HO
O
O
NN
O
OH
O
O
O
NN
O
OH
O
O
O
O
NN
O
O
O
O
HO
O
O
NN
O
Cl
HO
O
O
NN
NH
O
O
O
O
O
O
NN
NH
O
O
O
OO
HO
O
O
NN
NH
O
O
O
O
O
O
NN
NH
O
O
O
S
O
O
HO
O
O
NN
NH
O
O
O
PRODUCT +
IMPURITIES (A
GUMMY MASS)
(34) (35)
(36)
(37)
(39)
(37)
(33)
(37)
(38)
+
+
+
ace
tic
an
hy
dri
de
thio
nyl chlo
ride
phenyl chloroformate
meth
an
e su
lfon
yl
chl o
rid
e
DCC/HOBt
.....Scheme-1.13
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 30
Chapter - I
In yet another approach, acid group of 33 is activated with methane sulfonyl chloride, in
methylene chloride using N,N-diisopropyl ethyl amine as base. After reaction with methyl ester
of amino acid salts (40o), we obtained gummy mass, which solidified on keeping. 1H-NMR and
mass disclosed formation of 37 with 39 as process impurity. This impurity has a mass value of
m/z 463.
Finally, we opted to use DCC, HOBt as peptide coupling reagent for coupling of 33 with methyl
ester of amino acid salts (40o), to got desired product 37 with good purity and yield. The 1H
NMR and mass spectral data confirms the structure of 37. In the mass spectrum of 37 the
[M+H]+ was observed at m/z 386, and [M-H]
- was observed at m/z 384.2, which suggested the
molecular weight of 37 was 385. In 1H NMR spectrum (DMSO-d6) the chemical shift observed
at δ 3.63 ppm and δ 3.94 ppm both singlets confirms two methyl groups as ester of 1.
Following this successful methodology, around 20 analogs (37[a-t]) were prepared as described
schematically in Scheme-1.14. Dimethyl ester 37 was converted to 1, by treating with aqueous
alkaline solution Scheme-1.15. The detailed experimental procedure with analytical data of all
analogs are given in experimental section.
HO
HO
O
HO
O
O
H2N
O
OH
Methanol
SOCl2
HO
O
O
NN
O
OH
Methyl ester
of
Amino acids
DCC / HOBt
HO
O
O
NN
O
AA Ester
NaOH
HO
HO
O
NN
O
AA
(1a-t)
(10) (32)
water, Con. HCl
Aq. NaNO2 solution
(27)
(33) (37 [a-t])
(40 [a-t])
.....Scheme-1.14
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 31
Chapter - I
APPROACH D:
Positional isomers of Balsalazide have been prepared by coupling o-, m-, and p-isomers of nitro
benzoic acid with 4-hydroxy benzoic acid and salicylic acid. This is summarized schematically
in Scheme-1.15.
H2N
O
OH
O2N
OH
OO2N
O2NO
OH HO
O
O2N
O
NHHO
O
water / NaOH
SOCl2 / IPE
water / NaOH
SOCl2 / IPE
water / NaOH
SOCl2 / IPE
O2N
O2N
NH
O
OHO
O
HN
O
OH
water / NaOH
Pd/C, H2
water / NaOH
Pd/C, H2
water / NaOH
Pd/C, H2
H2N
O
NHHO
O
H2NNH
O
OHO
H2N
O
HN
O
OH
HO
HO
O
HO
O
OH
water, Con. HClAq. NaNO2
solution
NaOH, Na2CO3
water, Con. HClAq. NaNO2
solutionNaOH, Na2CO3
water, Con. HClAq. NaNO2
solutionNaOH, Na2CO3HO
HO
O
HO
HO
O
HO
O
OH
HO
O
OH
OHOH
O
NN
NH
O
OH
O
OH
NN
NH
O
OH
O
N
NH
O
O
HO
N
OH
O
OH
N
NH
O
O
HO
N
OH
NN
N
O
OHO
(40o)
(12) (41) (42)
(7) (43) (44)
(8) (45)(46)
(10) (10)(10)(31) (31)
(31)
(1) (16) (47) (48)
(49)
.
....Scheme-1.15
Synthesis of 1 and Decarboxy Balsalazide, 16, were already discussed in approach A. 47 and 48
are the meta analogs of 1 and 16. Both of the isomers are prepared starting from 3-nitrobenzoic
acid, 41 and β-alanine 40o. After amide formation, catalytic hydrogenation of 43 with Pd/C in
water yielded 45, which was diazotized with sodium nitrite in aqueous hydrochloride and
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 32
Chapter - I
coupled with sodium salicylate to give the desired compound 47 in excellent yield. The ESI
mass spectrum of 47 displayed peaks at m/z 356 [(M-H)-] in negative ion mode, and in positive
ion mode this compound appeared at m/z 358 [(M+H)+], suggests the mass of the product is m/z
357. In 1HNMR spectrum of compound 47, corresponding peaks at 7.69 (dd, J = 8.8 Hz, 1H),
7.99 and 8.02 (2dd, J = 8.8 Hz and J = 2.5 Hz, 2H), and 8.33 (dd, J = 2.5 Hz, 1H), represents
meta coupling of protons as J value is 2.5 Hz. The assigned structure for compound 47 is clearly
confirmed the above spectral data.
For preparation of 48, taken 45, and was diazotized with sodium nitrite in aqueous
hydrochloride and coupled with sodium salt of 4-hydroxy benzoic acid, 31 to give the desired
compound 48 in excellent yield. The ESI mass spectrum of 48 displayed peak in positive ion
mode and compound appeared at m/z 314 [(M+H)+], suggests the mass of the product is m/z
313. In 1HNMR spectrum of compound 48, corresponding peaks at 6.96 (d, J = 8.8 Hz, 2H) and
7.82 (d, J = 8.8 Hz, 2H) represents decarboxylated compound, where as δ values at 7.64 (dd, J
= 8.8 Hz, 1H), 8.15 (dd, J = 8.8 Hz and J = 2.5 Hz, 1H), 8.18 (dd, J = 8.8 Hz and J = 2.5 Hz,
1H), 8.62 (dd, J = 2.5 Hz, 1H) represents meta coupling of protons as J value 2.5 Hz. The
assigned structure for compound 48 is clearly confirmed the above spectral data.
Interestingly, when we tried to prepare 50 and 51, ortho analogs of 1 and 16, starting with 2-
nitrobenzoic acid 42, and follow the sequence as described in Scheme-1.16, we got 49 from 46.
This is exactly what we got from Makino et al[40]
work.
H2N
O
HN
O
OH
NN
N
O
OHO
HO
HO
O
HO
O
OH
water, Con. HClAq. NaNO2
solutionNaOH, Na2CO3
water, Con. HClAq. NaNO2
solutionNaOH, Na2CO3
N
O
HN
O
OH
N
HO
O
HO
N
O
HN
O
OH
N
HO(46)
(10)
(31)
(49)
(50)
(51)
.....Scheme-1.16
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 33
Chapter - I
The ESI mass spectrum of 49 displayed peak in positive ion mode and appeared at m/z 220
[(M+H)+] and m/z 242.2 as [(M+Na)
+] suggests the mass of the product is m/z 219. Analytical
data are available in experimental section.
CONCLUSION:
We have developed an excellent process to prepare Balsalazide in aqueous medium without
isolating any reaction intermediate. To have a thorough understanding of impurity formation
pathways of the anti-inflammatory drug Balsalazide Disodium, it is essential to have detail
information about the various possible impurities, metabolites and their synthetic routes. In
view of regulatory importance of the impurities in active pharmaceutical ingredient, a detail
study on various impurities in Balsalazide API was conducted. Different process related
impurities, degradation product and metabolites in Balsalazide API were identified, synthesized
and characterized by using various spectroscopic techniques like LCMS, Mass, 1
HNMR,
13CNMR, Infrared. A new process was developed for the preparation of Balsalazide (1) and
analogs starting from salicylic acid. Further, we have prepared different analogs, positional
isomers and metabolites.
EXPERIMENTAL SECTION:
SYNTHESIS OF 7:
To a suspension of 4-nitrobenzoic acid, 12 (200 g, 1.20 mole) in diisopropyl ether (2000 mL) ,
added thionyl chloride (164 g, 1.38 mole) and DMF (4g) at 30-35oC. The contents were heated
slowly to reflux at 65oC and stirred at the same temperature to complete the reaction. After
completion of reaction, the reaction mass was cooled to 5-10oC , and added to β-alanine, 40o
(127.9 g, 1.44 mole) in DM water (6000 mL) containing sodium hydroxide (127.8 g) at 5-15oC
maintaining pH >8 and the reaction mass was stirred at this temperature to complete the
reaction. After completion of the reaction the pH of the reaction mass was adjusted to 1.8 using
aqueous hydrochloric acid at 8-12oC and thereafter, product was filtered and washed with
precooled water to obtain 4-nitrobenzoyl-β-alanine, 7. Yield 271 g (95% of theory).
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 34
Chapter - I
Chromatographic purity: 99.53 % (by HPLC, area normalization). IR (KBr, cm-1
): 3379 (N-H),
3072 (Ar-CH), 1725 (C=O), 1626 and 1595 (C=C ring), 1411 (aliphatic CH), 799 and 776 (Ar-
H, out of plane bend). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.54 (t, 2H), 3.48 (m, 2H), 8.06
(d, J = 8.5 Hz, 2H), 8.32 (d, J = 8.5 Hz, 2H), 8.89 (t, J = 5.5 Hz, 1H), 12.28 (brs, 1H). MS m/z
(ESI): 237 [(M-H)-], Calculated; m/z 238.
SYNTHESIS OF 8:
To 4-nitrobenzoyl-β-alanine, 7 (260 g, 1.09 mole) suspended in D M water (780ml), sodium
carbonate (58 g, 0.55 mole) was added at 20-25oC and stirred the contents at 20-30
oC to obtain
clear solution. The reaction mass was hydrogenated at 20-35oC using 10% w/w Pd/C (5.2 g,
wet) and at 15-20 Kg pressure. After completion of reaction the reaction mass was filtered
under nitrogen atmosphere. Thereafter, added concentrated sulfuric acid (53.53 g, 0.55 mole) to
the filtrate at 20-25oC and stirred the reaction mass further at 5-10
oC to complete the
precipitation. The solids were filtered, washed with water and dried to yield 4-aminobenzoyl-β-
alanine, 8. Yield 202 g (89% of theory). Chromatographic purity: 99.42 % (by HPLC, by area
normalization). IR (KBr, cm-1
): 3418, 3334, 3241 (N-H), 3061 (Ar-CH), 1716 (C=O), 1619 and
1595 (C=C ring), 1458 (aliphatic CH), 1212 (C-N), 1077 (C-O), 796 and 785 (Ar-H, out of
plane bend). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.48 (t, 2H), 3.40(m, 2H), 5.60(brs, 2H),
6.53 (d, J = 8.5 Hz, 2H), 7.53 (d, J = 8.5 Hz, 2H), 8.05 (t, J = 5.5 Hz, 1H), 12.18 (brs, 1H). MS
m/z (ESI): 207.3 [(M-H)-], Calculated; m/z 208.
SYNTHESIS AND PURIFICATION OF 1:
To a suspension of 4-aminobenzoyl-β-alanine, 8 (80 g, 0.385mole) in DM water (960 mL)
added concentrated hydrochloric acid (80 mL) at 20-35oC. Filtered the reaction mass and cooled
to 2 to -2oC. Added aqueous sodium nitrite solution (27.86g, 0.403mol dissolved in 120ml D M
water), prepared separately, to the filtrate maintaining temperature 2 to -2oC. The resulting
diazotized solution was added to a solution of salicylic acid, 10 (63.7 g, 0.462mole in 1280ml
D M water containing 30.77g sodium hydroxide and 81.54 g sodium carbonate) at 2 to -2 oC
maintaining pH > 8. After completion of reaction, reaction mass was heated to 60-70oC and pH
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 35
Chapter - I
adjusted to 4.5 using concentrated hydrochloric acid. After a further maintaining the reaction
mass at 60-70oC for 3 hours it was slowly cooled to 40
oC, filtered, washed with water and dried
to yield mixture of Balsalazide and its monosodium salt. Yield 121 g (88% of theory).
Chromatographic purity: 99.27 % (by HPLC, by area normalization).
Balsalazide and its monosodium salt mixture (120g) was added to 50%w/v aqueous 1,4-dioxane
(120 ml) and heated the contents to 90-95oC. After maintaining temperature 90-95
oC for 10
minutes, the suspension was slowly cooled to 60-65oC, filtered, washed with water and dried to
yield mixture of Balsalazide and its monosodium salt. Yield 100g (73% of theory).
Chromatographic purity: 99.78 % (by HPLC, by area normalization). IR (KBr, cm-1
): 3371 and
3039 (OH and NH), 1705 and 1699 (C=O), 1634 (C=O amide), 1590 and 1538 (C=C aromatic),
1464 and 1404 (aliphatic C-H), 1229 (C-N), 1073 (C-O), 773 and 738 (Ar-H out of plane bend).
1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.54 (t, 2H), 3.50 (m, 2H), 6.95 (d, J = 8.8 Hz, 1H),
7.87 (d, J = 8.5 Hz, 2H), 8.02 (d, J = 8.5 Hz, 2H), 7.95 (dd, J = 8.8 Hz and 2.5 Hz, 1H), 8.34 (d,
J = 2.5 Hz, 1H), 8.68 (t, J = 5.5 Hz, 1H), 12.12 (brs, 1H). MS m/z (ESI): 356 [(M-H)-],
Calculated; m/z 357.
SYNTHESIS OF 13:
To a suspension of 4-aminobenzoic acid, 27 (30 g, 0.22 moles) in DM water (360 mL),
concentrated hydrochloric acid (30 mL, ~36% w/w)) was added at 20-25°C and thereafter
resultant solution was cooled to 2 to -2°C. To this solution, aqueous solution of sodium nitrite
(15.86 g, 0.23 moles) in DM water (60 mL) was added at 2 to -2°C. Thus obtained diazotized
solution was added to pre-cooled alkaline solution of salicylic acid (36.26 g, 0.26 moles) in DM
water (630 mL) containing sodium hydroxide (17.52 g) and sodium carbonate (46.42 g) at 2 to -
2°C, maintaining pH ≥ 8. After completion of reaction, reaction mass was heated to 60-65°C,
acidified and stirred for 3 h maintaining same temperature. Thereafter, resulting slurry was
cooled to 40°C, filtered, washed with DM water and dried to give compound 2 as brown
crystalline solid. (62.6 g, ~100% yield). IR (KBr, cm-1
): 3425 (O-H), 3072 (Ar-CH), 1686
(C=O), 1602 and 1587 (C=C ring), 1457 (aliphatic CH), 1208 (C-N), 1077 (C-O), 799 and 776
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 36
Chapter - I
(Ar-H, out of plane bend). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 6.96 (d, J = 8.8 Hz, 1H),
7.90 (d, J = 8.5 Hz, 2H), 7.98 (dd, J = 8.8 Hz and 2.5 Hz, 1H), 8.11 (d, J = 8.5 Hz, 2H), 8.34 (d,
J = 2.5 Hz, 1H), 13.20 (brs, 1H). 13
C NMR and DEPT (DMSO-d6, 300 MHz, δ ppm): 116.6(C),
118.2(CH), 122.1 (CH), 126.5 (CH), 128.0 (CH), 130.6 (CH), 131.9 (C), 143.5 (C), 154.6 (C),
166.8 (C), 166.9 (C), 171.1(C). MS m/z (ESI): 285.2 [(M-H)-], 307.0 [(M-H)
-+Na].
SYNTHESIS OF 14:
To a suspension of N-(4-aminobenzoyl) di-β-alanine (6 g, 0.02 mole) in DM water (72 mL),
concentrated hydrochloric acid (6 mL, ~36% w/w)) was added at 20-25°c and resultant solution
was cooled to 2 to -2°C. To this solution, aqueous solution of sodium nitrite (1.4 g, 0.02 mole)
in DM water (6 mL) was added at 2 to -2°C. Thereafter, resulting diazotized solution was added
to pre-cooled solution of salicylic acid (3.2 g, 0.02 mole) in (120 mL) DM water containing
sodium hydroxide (1.55 g) and sodium carbonate (4.15 g) at 2 to -2°C, maintaining pH ≥ 8.
After completion of reaction, resultant mass was heated to 60-65°c and acidified. Resulting
suspension was cooled to 30-35°C, filtered, washed with DM water and dried to obtain desired
product 3. (7.7 g, ~82% yield). IR (KBr, cm-1
): 3375 (O-H), 3019 (Ar-CH), 1675 (C=O), 1600
and 1577 (C=C ring), 1455 (aliphatic CH), 1212(C-N), 1067 (C-O), 795 and 770 (Ar-H, out of
plane bend). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.40 (m, 4H, 2CH2), 3.26 (m, 2H, CH2),
3.47 (m, 2H, CH2), 6.77 (d, J = 8.8 Hz, 1H), 7.83 (d, J = 8.8 Hz, 1H), 7.85 (d, J = 8.5 Hz, 2H),
7.97 (d, J = 8.5 Hz, 2H), 8.02 (t, J = 5.5 Hz, 1H), 8.28 (d, J = 2.5 Hz, 1H), 8.62 (t, J = 5.5 Hz,
1H), 12.21(brs, 1H). 13
C NMR and DEPT (DMSO-d6, 300 MHz, δ ppm): 34.8 (CH2), 35.6
(CH2), 36.2 (CH2), 37.1 (CH2), 118.9 (CH), 119.8 (C), 122.5 (CH), 123.4 (C), 127.2 (CH),
127.8 (CH), 129.2 (CH), 135.9 (C), 134.1 (C), 154.7 (C), 166.5 (C), 170.8 (C), 171.3 (C), 173.7
(C). MS m/z (ESI): 427.2 [(M-H)-], 449.0 [(M-H)
-+Na].
SYNTHESIS OF 15:
Concentrated hydrochloric acid (10 mL, ~36% w/w)) was added to a suspension of N-(4-
aminobenzoyl) β-alanine (10 g, 0.05 mole) in DM water (145 mL) at 20-25°C. Obtained clear
solution was cooled to 0 to -2°C and a solution of sodium nitrite (3.5 g, 0.05 mole) in DM water
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 37
Chapter - I
(20 mL) was added to it. Thus obtained, diazotized solution was added to a solution of salicylic
acid (8 g, 0.06 mole) in water / isopropyl alcohol mixture (1:1, 150 mL) containing sodium
carbonate (18 g) at 2 to -2°C, maintaining pH ≥ 8. After completion of reaction, reaction mass
acidified, filtered, washed and dried. Thereafter, desired impurity Balsalazide 3-isomer 4 was
purified by flash chromatography (ethyl acetate / methanol as eluant) to get brown solid. (1.2 g,
7% yield). IR (KBr, cm-1
): 3426 and 3185 (OH and NH), 1717 and 1711 (C=O), 1631(C=O
amide), 1572 and 1545 (C=C aromatic), 1444 and 1399 (aliphatic C-H), 1229 (C-N), 1071 (C-
O), 771 and 736 (Ar-H out of plane bend). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.52 (m,
2H, CH2), 3.47 (m, 2H, CH2), 6.61 (dd, J = 7.7 Hz, 1H), 7.57 (dd, J = 8.0 Hz and 1.7 Hz, 1H),
7.86 (d, J = 8.2 Hz, 2H), 7.87 (dd, J = 8.0 Hz and 1.7 Hz, 1H), 8.00 (d, J = 8.5 Hz, 2H), 8.70 (t,
J = 5.5 Hz, 1H), 18.43 (brs, 1H). 13
C NMR and DEPT (DMSO-d6, 300 MHz, δ ppm): 35.0
(CH2), 36.7 (CH2), 115.1 (CH), 119.3 (CH), 122.8 (CH), 123.5 (C), 129.1 (CH), 135.0 (CH),
136.1 (C), 142.1 (C), 155.0 (C), 165.5 (C), 166.4 (C), 171.4 (C), 174.1 (C). MS m/z (ESI): 356.2
[(M-H)-], 378.0 [(M-H)
-+Na].
SYNTHESIS OF 16:
To a suspension of N-(4-aminobenzoyl)-β-alanine (20 g, 0.1 mole) in DM water (300 mL)
concentrated hydrochloric acid (20 mL, ~36% w/w) was added at 20-25°c, and resulting clear
solution was cooled to 2 to -2°C. To the obtained solution, aqueous solution of sodium nitrite
(6.88 g, 0.1 mole) in DM water (20 mL) was added at 2 to -2°c. Thus obtained, diazotized
solution was added slowly to pre-cooled solution of 4-hydroxybenzoic acid (13.53 g, 0.1 mole)
in DM water (200 mL), containing (8.15 g) of sodium hydroxide and (15.9 g) of sodium
carbonate at 2 to -2°C, maintaining pH ≥ 8. Thereafter, after completion of reaction, reaction
mass was acidified, filtered, washed and dried to obtain the desired Impurity 5. (27.38 g, 91%
yield). IR (KBr, cm-1
): 3336 (OH and NH); 3048 (Ar-H); 2969 (aliphatic C-H); 1707 and 1606
(C=O); 1589 and 1543 (C=C aromatic); 1464 (aliphatic C-H); 1228 (C-N) 1087 (C-O), 774 and
724 (Ar-H out of plane bend). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.54 (m, 2H, CH2), 3.50
(m, 2H, CH2), 6.97 (d, J = 8.8 Hz, 2H), 7.84 (d, J = 8.8 Hz, 2H), 7.88 (d, J = 8.8 Hz, 2H), 8.04
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 38
Chapter - I
(d, J = 8.8 Hz, 2H), 8.72 (t, J = 5.5 Hz, 1H), 10.47 (brs, 1H), 12.30 (brs, 1H). 13
C NMR and
DEPT (DMSO-d6, 300 MHz, δ ppm): 33.8 (CH2), 35.7 (CH2), 116.1 (CH), 121.9 (CH), 125.2
(CH), 128.4 (CH), 135.6 (C), 145.3 (C), 153.6 (C), 161.5 (C) , 165.6 (C), 172.9 (C). MS m/z
(ESI): 314.0 [(MH)+], 336.0 [M
++Na].
SYNTHESIS OF 17:
To a suspension of N-(4-aminobenzoyl)-β-alanine (20 g, 0.1 mole) in DM water (250 mL)
concentrated hydrochloric acid (20 mL, ~36 % w/w) was added at 20-25°C. Resulting clear
solution was cooled to 2 to --2°C and (6.7 g, 0.1 mole) of sodium nitrite in DM water (30 mL)
was added to it .Thus obtained, diazotized solution was added to a pre-cooled solution of
salicylic acid (6.6 g, 0.05mole) in DM water (300 mL) containing sodium hydroxide (7.68 g)
and sodium carbonate (15.26 g) at 2 to -2°C and maintaining pH above 8. After addition,
reaction mass was acidified, filtered, washed with DM water and dried. Thereafter, desired
impurity was purified by flash chromatography. IR (KBr, cm-1
): 3440 and 3178 (OH and NH),
2968 and 2975 (aliphatic C-H), 1713 and 1631 (C=O), 1548 and 1493 (C=C aromatic), 1451
(aliphatic C-H), 1242 (C-N), 1074 (C-O), 772 and 739 (Ar-H out of plane bend). 1H NMR
(DMSO-d6, 300 MHz, δ ppm): 2.47 (m, 4H, 2CH2), 3.48 (m, 4H, 2CH2), 7.90 (2d, J = 8.8 Hz,
4H), 8.01 (2d, J = 8.8 Hz, 4H), 8.15 (d, J = 2.5 Hz, 1H), 8.51 (d, J = 2.5 Hz, 1H), 8.70 and 8.74
(2t, J = 5.2 Hz, 2H), 18.89 (brs, 1H). 13
C NMR and DEPT (DMSO-d6, 300 MHz, δ ppm): 34.2
(CH2), 35.9 (CH2), 113.7 (CH), 121.2 (C), 121.7 (CH), 122.2 (CH), 128.3 (CH), 128.8 (CH),
135.2 (C), 135.6 (C), 139.5 (C), 142.4 (C), 153.7 (C), 154.0 (C), 165.5 (C), 169.5 (C), 171.2
(C), 173.2 (C). MS m/z (ESI): 577.2 [(MH)+], 599.0 [M
++Na].
SYNTHESIS OF 18:
This related substance was prepared in laboratory as described in previous example. IR (KBr,
cm-1
): 3446 and 3180 (OH and NH), 2960 and 2971 (aliphatic C-H), 1720 and 1635 (C=O),
1552 and 1490 (C=C aromatic), 1443 (aliphatic C-H), 1248 (C-N), 1076 (C-O), 775 and 731
(Ar-H out of plane bend). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.54 (m, 4H, 2CH2), 3.49 (m,
4H, 2CH2), 6.70 (d, J = 8.8 Hz, 1H), 7.58 (d, J = 8.5 Hz, 2H), 7.60 (dd, J = 8.8 Hz and 2.5 Hz,
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 39
Chapter - I
1H), 7.70 (d, J = 8.8 Hz, 1H), 7.93 (d, J = 8.5 Hz, 2H), 7.97 (dd, J = 8.8 Hz and 1.4 Hz, 1H),
8.05 (d, J = 1.4 Hz, 1H), 8.17 (d, J = 2.5 Hz, 1H), 8.64 (t, J = 5.2 Hz, 1H), 8.77 (t, J = 5.2 Hz,
1H), 18.34 (brs, 1H). 13
C NMR and DEPT (DMSO-d6, 300 MHz, δ ppm): 34.6 (CH2), 36.5
(CH2), 116.9 (CH), 119.2 (CH), 119.9 (C), 126.2 (CH), 127.5 (CH), 128.6 (CH), 129.4 (CH),
130.4 (CH), 131.3 (CH), 134.0 (C), 135.6 (C), 138.7 (C), 141.9 (C), 143.5 (C), 151.8 (C), 166.4
(C), 166.8 (C), 171.1 (C), 173.8 (C). MS m/z (ESI): 549.2 [(MH)+], 571.0 [M
++Na].
SYNTHESIS OF 19:
To a suspension of N-(4-aminobenzoyl)-β-alanine (5 g, 0.024 mole) in DM water (75 mL),
added concentrated hydrochloric acid (5 mL, ~36% w/w) at 20-25°C and the resulting solution
was cooled to 2 to -2°C. A solution of sodium nitrite (1.74 g, 0.025 mole) in DM water (10 mL)
was added at 2 to -2°C. The resulting diazotized solution was added to a pre-cooled solution of
4-hydroxybenzoic acid (1.65 g, 0.012 mole) in DM water (100 mL) containing sodium
carbonate (9.1 g) at 2 to -2°C and maintaining pH above 8. After completion of reaction,
reaction mass acidified, filtered, washed with DM water and dried. Thereafter, obtained product
was suspended in aqueous acetic acid (400 mL) and refluxed for 20 min. Cooled the suspension
to 25-30°C, filtered and dried to obtain impurity 8. (4.28 g, 32% yield). IR (KBr, cm-1
): 3298
(NH), 3057 (Ar-H), 2921 (aliphatic C-H), 1630 and 1604 (C=O), 1577 and 1538 (C=C
aromatic), 1430 (C-H), 1214 (C-N), 1085 (C-O), 799 and 772 (Ar-H out of plane bend). 1H
NMR (DMSO-d6, 300 MHz, δ ppm): 2.57 (m, 4H, 2CH2), 3.52 (m, 4H, 2CH2), 7.32 (d, J = 8.8
Hz, 1H), 7.94 (d, J = 8.2 Hz, 1H), 7.95-8.15 (m, 8H), 8.24 (s, 1H), 8.72 and 8.75 (2t, J = 5.2 Hz,
2H), 11.54 (brs, 1H), 12.27 (brs, 2H). 13
C NMR and DEPT (DMSO-d6, 300 MHz, δ ppm): 33.7
(CH2), 35.7 (CH2), 114.1 (CH), 119.3 (CH), 122.2 (CH), 122.8 (CH), 128.0 (CH), 128.4 (CH),
128.5 (CH), 136.1 (C), 136.5 (C), 139.0 (C), 145.1 (C), 153.2 (C), 153.3 (C), 159.0 (C), 165.5
(C), 165.5 (C), 172.9 (C). MS m/z (ESI): 533.3 [(MH)+], 555.1 [M
++Na].
SYNTHESIS OF 20:
Suspended (10 g, 0.05 mole) N-(4-aminobenzoyl)-β-alanine in DM water (120 mL) at 20-25°C.
Added concentrated hydrochloric acid (10 mL, ~36% w/w) to the obtained suspension and
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 40
Chapter - I
cooled to 2 to -2°C. A solution of sodium nitrite (3.5 g, 0.05 mole) in DM water (20 mL) was
added at 2 to -2°C. Resulting diazotized solution was added to a solution of 4-hydroxybenzoic
acid (1.65 g, 0.01mole) in DM water (100 mL) containing sodium carbonate (18 g) at 2 to -2°C
maintaining pH above 8. After completion of reaction, temperature of reaction mass was raised
to 35-40°C and acidified,. Thereafter, precipitated product was filtered, washed and dried.
Obtained product was suspended in ethyl methyl ketone (100 mL) having 10% v/v water and
refluxed for 20min. Thereafter, suspension was cooled to 20-25°C, filtered and dried to obtain
product 9. (3.15 g, 36% yield). IR (KBr, cm-1
): 3261 (OH and NH), 1714 and 1639 (C=O), 1548
and 1494 (C=C aromatic), 1228 (aliphatic C-N), 1070 (C-O), 789 and 760 (Ar-H out of plane
bend). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.41 (m, 4H, 2CH2), 2.47 (m, 2H, CH2), 3.43
(m, 4H, 2CH2), 3.49 (m, 2H, CH2), 6.98 (d, J = 9.3 Hz, 1H), 7.43 (d, J = 8.2 Hz, 2H), 7.51 (2d, J
= 8.8 Hz and 2.5 Hz, 4H), 7.87 (d, J = 8.0 Hz, 6H), 7.93 (d, J = 9.3 Hz, 1H), 8.55, 8.64 and 8.72
(3t, J = 5.2 Hz, 3H). 13
C NMR and DEPT (DMSO-d6, 300 MHz, δ ppm): 37.3 (CH2), 37.4
(CH2), 38.4 (CH2), 121.6 (CH), 123.8 (CH), 124.2 (CH), 124.3 (CH), 127.4 (CH), 130.4 (CH),
130.6 (CH), 134.6 (CH), 135.1 (C), 136.5 (C), 137.7 (C), 138.4 (C), 139.8 (C), 144.3 (C), 146.5
(C), 154.0 (C), 155.7 (C), 158.2 (C), 167.6 (C), 167.8 (C), 168.6 (C), 176.5 (C), 176.8 (C). MS
m/z (ESI): 724.1 [(MH)+], 746.2 [M
++Na].
SYNTHESIS OF N-acetyl-8:
Added N-(4-aminobenzoyl)-β-alanine (30 g, 0.15 mole) to acetic acid / water mixture (2:1, 90
mL), at 25-30°C. Acetic anhydride (30 g, 0.29 mole) was added to the obtained suspension
maintaining temperature 30-45°C. Stirred the reaction mass at 35-40°C for 1h.and diluted with
acetone (90 mL), Thus, precipitated product was filtered, washed with DM water followed by
acetone and dried to obtain 10. (32.46 g, 90% yield). IR (KBr, cm-1
): 3326 and 3196 (OH and
NH), 3064 (Ar-H), 2907 (aliphatic C-H), 1706, 1693 and 1626 (C=O), 1590 and 1537 (C=C
aromatic), 1429 (aliphatic C-H), 1262 (C-N), 1083 (C-O), 813 and 763 (Ar-H out of plane
bend). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.06 (s, 3H, CH3), 2.48 (t, 2H, CH2), 3.44 (m,
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 41
Chapter - I
2H, CH2), 7.62 (d, J = 8.5 Hz, 2H), 7.77 (d, J = 8.5 Hz, 2H), 8.38 (t, J = 5.2 Hz, 1H), 10.13 (s,
1H).
SYNTHESIS OF N-acetyl-2:
Added 5-aminosalicylic acid (50 g, 0.33 mole) to acetic acid / acetic anhydride mixture (1:1,
100 mL) and stirred the contents at reflux for 30min, cooled to 20-25°C. Filtered the
precipitated product, washed with DM water. Suspended the obtained product in 10% w/w
aqueous sodium hydroxide solution and stirred for 1h at 25-30°C. Adjusted the pH of solution
to 2.to precipitate the product. Filtered the product 11, washed with DM water and dried. (59.7
g, 94% yield). IR (KBr, cm-1
): 3357 and 3106 (OH and NH), 2874 (aliphatic C-H), 1685 and
1603 (C=O), 1539 and 1516 (C=C aromatic), 1420 (aliphatic C-H), 1238 (C-N), 807 and 792
(Ar-H out of plane bend). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.14 (s, 3H, CH3), 7.07 (dd, J
= 8.78 Hz and 1.92 Hz, 1H), 7.32 (d, J = 1.92 Hz, 1H), 7.74 (d, J = 8.78 Hz, 1H), 9.60 (s, 1H),
11.32 (brs, 1H).
SYNTHESIS OF 21:
To a suspension of 4-nitrobenzoyl-β-alanine, 7 (25 g, 0.11 mole) in diisopropyl ether (250 mL) ,
added thionyl chloride (15 g, 0.13 mole) and DMF (1g) at 30-35oC. The contents were heated
slowly to reflux at 65oC and stirred at the same temperature to complete the reaction. After
completion of reaction, the reaction mass was cooled to 5-10oC , and added to β-alanine, 40o
(11.21 g, 0.12 mole) in DM water (500 mL) containing sodium hydroxide (12 g) at 5-15oC
maintaining pH >8 and the reaction mass was stirred at this temperature to complete the
reaction. After completion of the reaction the pH of the reaction mass was adjusted to 1.8 using
aqueous hydrochloric acid at 8-12oC and thereafter, product was filtered and washed with
precooled water to obtain N-(2-(3-hydroxypropylcarbamoyl)ethyl)-4-nitrobenzamide (21).
Yield 6.8 g, (20% of theory). Chromatographic purity: 99.53 % (by HPLC, area normalization).
1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.38 (t, 2H, CH2), 2.62 (t, 2H, CH2), 3.26 (m, 2H,
CH2), 3.47 (m, 2H, CH2), 8.08 (d, J = 8.5 Hz, 2H), 8.33 (d, J = 8.5 Hz, 2H), 8.92 (m, J = 5.5 Hz,
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 42
Chapter - I
2H), 12.28 (brs, 1H). MS m/z (ESI): 308 [(M-H)-], m/z 310.1 [(M+H)
+], m/z 332.1
[(M+H)++Na].
SYNTHESIS OF 25:
To 4-nitrobenzoyl-β-alanine, 7 (260 g, 1.09 mole) suspended in ethanol (3400 mL) at 20-25oC
and stirred the contents at 20-30oC to obtain clear solution. The reaction mass was hydrogenated
at 20-35oC using 10% w/w Pd/C (18.2 g, wet) and at 15-20 Kg pressure. After completion of
reaction the reaction mass was filtered under nitrogen atmosphere and concentrated to remove
solvent. Thereafter, diluted with water (3120 mL), concentrated hydrochloric acid (260 mL) was
added at 20-25oC and stirred the reaction mass further at 5-10
oC to dissolve 8. The solids were
filtered, washed with water and dried to yield a mixture of 25 and 26. This was separated
through column chromatography. Yield 2.5 g, 25. 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.57
(t, 4H, CH2), 3.54 (m, 4H, CH2), 8.01 (d, J = 8.5 Hz, 4H), 8.06 (d, J = 8.5 Hz, 4H), 8.77 (t, J =
5.5 Hz, 2H), 12.30 (brs, 2H). MS m/z (ESI): 411.4 [(M-H)-], m/z 413 [(M+H)
+], m/z 435.1
[(M+Na)+], m/z 457.2 [(M+2Na)
+].
SYNTHESIS OF 26:
Same process as described in 25. Yield 4.3 g, 26. 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.56
(t, 4H, CH2), 3.40 (m, 4H, CH2), 6.70 (d, J = 8.5 Hz, 4H), 7.65 (d, J = 8.5 Hz, 4H), 8.17 (t, J =
5.5 Hz, 2H), 8.23 (s, 2H), 12.21 (brs, 2H). MS m/z (ESI): 413.3 [(M-H)-], m/z 415.2 [(M+H)
+],
m/z 437.3 [(M+Na)+].
SYNTHESIS OF 27:
To 4-nitrobenzoic acid, 12 (100 g, 0.6 mole) suspended in D M water (500 mL), sodium
hydroxide (24 g, 0.6 mole) was added at 20-25oC and stirred the contents at 20-30
oC to obtain
clear solution. The reaction mass was hydrogenated at 20-35oC using 10% w/w Pd/C (2 g, wet)
and at 15-20 Kg pressure. After completion of reaction the reaction mass was filtered under
nitrogen atmosphere. Thereafter, added concentrated sulfuric acid (29.35 g, 0.3 mole) to the
filtrate at 20-25oC and stirred the reaction mass further at 5-10
oC to complete the precipitation.
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 43
Chapter - I
The solids were filtered, washed with water and dried to yield 4-aminobenzoic acid, 27. Yield
70 g (85% of theory). Chromatographic purity: 99.68 % (by HPLC, by area normalization). 1H
NMR (DMSO-d6, 300 MHz, δ ppm): 5.87 (s, 2H, NH2), 6.55 (d, J = 8.5 Hz, 2H), 7.62 (d, J =
8.5 Hz, 2H), 11.96 (brs, 1H). MS m/z (ESI): 136 [(M-H)-], m/z 138 [(M+H)
+].
SYNTHESIS OF 1a-t: (General procedure for In-situ reaction)
To a suspension of 4-nitrobenzoic acid, 12 (200 g, 1.20 mole) in diisopropyl ether (2000 mL) ,
added thionyl chloride (164 g,1.38 mole) and DMF (4g) at 30-35oC. The contents were heated
slowly to reflux at 65oC and stirred at the same temperature to complete the reaction. After
completion of reaction, the reaction mass was cooled to 5-10oC , and added to amino acids,
40(a-t), (1.44 mole) in DM water (6000 mL) containing sodium hydroxide (127.8 g) at 5-15oC
maintaining pH >8 and the reaction mass was stirred at this temperature to complete the
reaction. After completion of the reaction the lower aqueous layer was separated containing 7(a-
t). Thereafter, the reaction mass was hydrogenated at 20-45oC using 10% Pd/C (2% w/w, based
on 12) and at 15-20 Kg/cm2
pressure. After completion of reaction the catalyst was filtered off
under nitrogen atmosphere (containing 8(a-t)), added DM water (1000 mL) and concentrated
hydrochloric (200mL, 36% w/w) to the filtrate at 20-35oC. Filtered the reaction mass and cooled
to 2 to -2oC. Added aqueous sodium nitrite solution (1.25 mole in 400mL DM water) to the
obtained filtrate maintaining temperature 2 to -2 oC. Resulting diazotized solution was added to
a solution of salicylic acid, 10 (1.44 mole in 2400 mL D M water containing sodium hydroxide
and sodium carbonate) at 2 to -2oC maintaining pH > 8. After completion of reaction, reaction
mass was heated to 60-70oC and pH adjusted to 4.2 using concentrated hydrochloric acid.
Further maintaining temperature 60-70oC for 3 hours the reaction mass was slowly cooled to
30oC, filtered, washed with water and dried to yield 1(a-t).
This crude 1(a-t), (65 g) was added to 50%w/v aqueous 1,4-dioxane (195mL) and heated the
contents to 90-95oC. After maintaining temperature 90-95
oC for 10 minutes, the suspension was
slowly cooled to 60-65oC, filtered, washed with water and dried to yield pure 1(a-t).
Chromatographic purity: >99.00 %. (by HPLC, by area normalization).
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 44
Chapter - I
The analytical data of all analogs are given in Table-1.13.
SYNTHESIS OF 32:
To salicylic acid, 10 (50 g, 0.36 mole) suspended in methanol (400 mL), DMF (1 mL, cat.) was
added at 20-25oC and then thionyl chloride (51.74 g, 0.44 mole) at 22-30
oC. The reaction mass
was heated to reflux at 60-70oC. After completion of reaction (checked by TLC), the reaction
mass was concentrated to remove solvents. Thereafter, diluted with methylene chloride (100
mL) and water (50 mL), adjusted pH to 9.8 with aqueous ammonia solution. Methylene chloride
layer was separated, washed with water (50 mL) and concentrated under reduced pressure to get
32 as an oil. Yield 50 g (91% of theory). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 3.89 (s, 3H,
CH3), 6.96 (m, J = 8.5 Hz and J = 2.5 Hz, 2H), 7.53 (m, J = 8.5 Hz and J = 2.5 Hz, 1H), 7.79
(m, J = 8.5 Hz and J = 2.5 Hz, 1H), 10.51 (s, 1H). MS m/z (ESI): 151 [(M-H)-].
SYNTHESIS OF 33:
To a suspension of 4-aminobenzoic acid, 27 (30 g, 0.22mole) in DM water (360 mL) added
concentrated hydrochloric acid (30 mL) at 20-35oC. Filtered the reaction mass and cooled to 2
to -2oC. Added aqueous sodium nitrite solution (15.86 g, 0.23mole dissolved in 60 mL D M
water), prepared separately, to the filtrate maintaining temperature 2 to -2oC. The resulting
diazotized solution was added to a solution of methyl salicylate, 32 (40 g, 0.26 mole in 630 mL
D M water containing 17.52g sodium hydroxide and 46.42 g sodium carbonate) at 2 to -2 oC
maintaining pH > 8. After completion of reaction, reaction mass was heated to 15-20oC and pH
adjusted to 6.5 to 7 using concentrated hydrochloric acid. After that, raised the temperature to
50-55oC and pH adjusted to 2. A further maintaining the reaction mass at 50-55
oC for 3 hours
and was slowly cooled to 40oC, filtered, washed with water and dried to yield 33. Yield 60.23 g
(92% of theory). Chromatographic purity: 99.21 % (by HPLC, by area normalization). 1H NMR
(DMSO-d6, 300 MHz, δ ppm): 3.94 (s, 3H, CH3), 7.22 (d, J = 8.8 Hz, 1H), 7.93 (d, J = 8.5 Hz,
2H), 8.10 (dd, J = 8.8 Hz and J = 2.5 Hz, 1H), 8.14 (d, J = 8.5 Hz, 2H), 8.34 (d, J = 2.5 Hz, 1H),
11.01 (s, 1H), 13.21 (brs, 1H). MS m/z (ESI): 299.2 [(M-H)-], m/z 300.8 [(M+H)
+].
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 45
Chapter - I
SYNTHESIS OF 37a-t: (General procedure)
Placed DCC (3.61 g, 0.017 mole), to methylene chloride (50 mL) at 20-25oC. 33 (5 g, 0.016
mole) and methyl ester hydrochloride salt of β-alanine, 40(a-t) (0.018 mole) were added to
above reaction mass, followed by cat. HOBt (0.45 g, 0.003 mole) at 20-25oC. Thereafter,
DIPEA (2.58 g, 0.02 mole) was added slowly at 20-25oC, and maintained stirring for 18hr. After
completion of reaction, cooled to 0-2oC and maintained for 1hr. Filtered out DCU and washed
with chilled methylene chloride. Obtained filtrate was washed consequently with 10% aqueous
hydrochloric acid, 10% aqueous ammonia and then with water. Methylene chloride layer was
concentrated and concentrated mass was taken in to water (20 mL). It was stirred for 2hr to get a
solid. Filtered, washed with water and dried to get the desired compound, 37(a-t) in good
quality. Yield 5.8 g (91% of theory).
The analytical data of all analogs are given in Table-1.14.
SYNTHESIS OF 1a-t: (general procedure)
To a suspension of 37(a-t) (0.013 mole) in DM water (50 mL) added 50% aqueous sodium
hydroxide solution (2.2 mL, 0.027 mole) at 20-35oC. Stirred the reaction mass at 25-35
oC to
complete the hydrolysis. After that, raised the temperature to 50-55oC and pH adjusted to 2. A
further maintaining the reaction mass at 50-55oC for 3 hours and was slowly cooled to 40
oC,
filtered, washed with water and dried to yield 1(a-t). Yield 4.28 g (92% of theory). Analytical
data given in Table-1.13.
SYNTHESIS OF 43:
Followed same operating parameters as described in synthesis of 7. 3-nitrobenzoic acid, 41 was
used as a starting material. Yield 26.3 g (92% of theory). 1H NMR (DMSO-d6, 300 MHz, δ
ppm): 2.56 (m, 2H, CH2), 3.50 (m, 2H, CH2), 7.78 (t, J = 8.5 Hz, 1H), 8.29 (m, J = 8.8 Hz and J
= 2.5 Hz, 1H), 8.38 (m, J = 8.8 Hz and J = 2.5 Hz, 1H), 8.68 (t, J = 2.5 Hz, 1H), 8.95 (t, J = 5.5
Hz, 1H), 12.25 (brs, 1H). MS m/z (ESI): 237.2 [(M-H)-], m/z 239.2 [(M+H)
+].
SYNTHESIS OF 44:
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 46
Chapter - I
Followed same operating parameters as described in synthesis of 7. 2-nitrobenzoic acid, 42 was
used as a starting material. Yield 25.1 g (88% of theory). 1H NMR (DMSO-d6, 300 MHz, δ
ppm): 2.52 (t, 2H, CH2), 3.43 (m, 2H, CH2), 7.57 (dd, J = 8.5 Hz and J = 2.5 Hz, 1H), 7.69 (ddd,
J = 8.5 Hz, J = 8.5 Hz and J = 2.5 Hz, 1H), 7.77 (ddd, J = 8.5 Hz, J = 8.5 Hz and J = 2.5 Hz,
1H), 8.03 (dd, J = 8.5 Hz and J = 2.5 Hz, 1H), 8.74 (t, J = 5.5 Hz, 1H), 12.27 (brs, 1H). MS m/z
(ESI): 237.2 [(M-H)-], m/z 239.2 [(M+H)
+].
SYNTHESIS OF 45:
Followed same operating parameters as described in synthesis of 8. 3-nitrobenzoyl-β-alanine, 43
was used as a starting material. Yield 20 g (92% of theory). 1H NMR (DMSO-d6, 300 MHz, δ
ppm): 2.46 (t, 2H, CH2), 3.40 (m, 2H, CH2), 5.60 (brs, 2H, NH2), 6.83 (dd, J = 2.5 Hz, 1H), 7.08
(dd, J = 8.8 Hz and J = 2.5 Hz, 1H), 7.15 (dd, J = 8.8 Hz and J = 2.5 Hz, 1H), 7.20 (dd, J = 8.8
Hz and J = 2.5 Hz, 1H), 8.33 (t, J = 5.5 Hz, 1H), 11.91 (brs, 1H). MS m/z (ESI): 207.2 [(M-H)-
], m/z 209.2 [(M+H)+].
SYNTHESIS OF 46:
Followed same operating parameters as described in synthesis of 8. 2-nitrobenzoyl-β-alanine, 44
was used as a starting material. Yield 18.7 g (86% of theory). 1H NMR (DMSO-d6, 300 MHz, δ
ppm): 2.55 (t, 2H, CH2), 3.48 (m, 2H, CH2), 5.20 (brs, 2H, NH2), 6.71 (dd, J = 8.8 Hz and J =
2.5 Hz, 1H), 6.84 (dd, J = 8.8 Hz and J = 2.5 Hz, 1H), 7.23 (ddd, J = 8.8 Hz and J = 2.5 Hz,
1H), 7.67 (dd, J = 8.8 Hz and J = 2.5 Hz, 1H), 8.54 (t, J = 5.5 Hz, 1H), 9.09 (s, 1H). MS m/z
(ESI): 207.2 [(M-H)-], m/z 209.2 [(M+H)
+].
SYNTHESIS OF 47:
Followed same operating parameters as described in synthesis of 1. 3-aminobenzoyl-β-alanine,
45 was used as a starting material. Yield 60 g (100% of theory). IR (KBr, cm-1
): 3279 (OH and
NH); 3062 (Ar-H); 2632 (aliphatic C-H); 1696 and 1654 (C=O); 1632 and 1539 (C=C
aromatic); 1491 and 1452 (aliphatic C-H); 1212 (C-N) 1075 (C-O), 897 and 712 (Ar-H out of
plane bend). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.56 (t, 2H, CH2), 3.50 (m, 2H, CH2), 7.18
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 47
Chapter - I
(d, J = 8.8 Hz, 1H), 7.69 (dd, J = 8.8 Hz, 1H), 7.99 and 8.02 (2dd, J = 8.8 Hz and J = 2.5 Hz,
2H), 8.12 (dd, J = 8.8 Hz and J = 2.5 Hz, 1H), 8.33 (dd, J = 2.5 Hz, 1H), 8.38 (d, J = 2.5 Hz,
1H), 8.76 (t, J = 5.5 Hz, 1H). MS m/z (ESI): 356 [(M-H)-], m/z 358 [(M+H)
+].
SYNTHESIS OF 48:
Followed same operating parameters as described in synthesis of 16. 3-aminobenzoyl-β-alanine,
45 was used as a starting material. Yield 26.6 g (88% of theory). 1H NMR (DMSO-d6, 300
MHz, δ ppm): 2.58 (m, 2H, CH2), 3.47 (m, 2H, CH2), 6.96 (d, J = 8.8 Hz, 2H), 7.82 (d, J = 8.8
Hz, 2H), 7.64 (dd, J = 8.8 Hz, 1H), 8.15 (dd, J = 8.8 Hz and J = 2.5 Hz, 1H), 8.18 (dd, J = 8.8
Hz and J = 2.5 Hz, 1H), 8.62 (dd, J = 2.5 Hz, 1H), 8.75 (t, J = 5.5 Hz, 1H), 12.30 (brs, 1H). MS
m/z (ESI): 314.0 [(MH)+], 336.0 [(M+Na)
+].
SYNTHESIS OF 49:
Followed same operating parameters as described in synthesis of 1. 2-aminobenzoyl-β-alanine,
46 was used as a starting material. Yield 30 g . IR (KBr, cm-1
): 2930 (Ar-H), 2804 (aliphatic C-
H), 1719 and 1694 (C=O), 1601 and 1577 (C=C aromatic), 1441 (C-H) 783 and 692 (Ar-H out
of plane bend). 1H NMR (DMSO-d6, 300 MHz, δ ppm): 2.87 (t, 2H, CH2), 4.59 (t, 2H, CH2),
7.94 (m, J = 8.5 Hz and J = 2.5 Hz , 1H), 8.10 (m, J = 8.5 Hz and J = 2.5 Hz , 1H), 8.21 (m, J =
8.5 Hz and J = 2.5 Hz , 1H), 8.26 (m, J = 8.5 Hz and J = 2.5 Hz , 1H), 12.46 (brs, 1H). MS m/z
(ESI): 218 [(M-H)-], m/z 220 [(M+H)
+], 242.2 [(M+Na)
+].
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 48
Chapter - I
Table-1.13
S. No. COMPOUND 7 1
1 a 3.97 (d, J = 6 Hz, 2H), 8.12 (d, J = 9 Hz, 2H), 8.35 (d,
J = 9 Hz, 2H), 9.23 (t, J = 6 Hz, 1H), 12.70 (brs, 1H).
MS m/z (ESI): 223 [(M-H)-], Calculated; m/z 224.
3.98 (d, J = 3 Hz, 2H), 7.11 (d, J = 8.7 Hz, 1H), 7.95 (d, J = 9 Hz,
2H), 8.08 (d, J = 9 Hz, 2H), 8.12 (dd, J = 3 Hz and J = 9 Hz, 1H),
8.38 (d, J = 3 Hz, 1H), 9.05 (t, J = 6 Hz, 1H), 12.18 (brs, 1H).
MS m/z (ESI): 342.1 [(M-H)-], Calculated; m/z 343.
2 b 1.42 (d, J = 9 Hz, 3H), 4.44 (m, J = 9 Hz and J = 6 Hz,
1H), 8.12 (d, J = 9 Hz, 2H), 8.32 (d, J = 9 Hz, 2H),
9.05 (d, J = 6 Hz, 1H), 12.69 (brs, 1H).
MS m/z (ESI): 237 [(M-H)-], 239.1 [(M+H)
+],
Calculated; m/z 238.
1.43 (d, J = 6 Hz, 3H), 4.46 (m, J = 9 Hz and J = 6 Hz, 1H), 7.19 (d, J
= 9 Hz, 1H), 7.96 (d, J = 9 Hz, 2H), 8.11 (d, J = 9 Hz, 2H), 8.14 (d, J
= 3 Hz and J = 9 Hz, 1H), 8.39 (d, J = 3 Hz, 1H), 8.88 (d, J = 9 Hz,
1H), 12.28 (brs, 2H).
MS m/z (ESI): 356.1 [(M-H)-], 358.2 [(M+H)
+], Calculated; m/z 357.
3 c 1.00 (dd, J = 6 Hz, 6H), 2.20 (m, J = 6 Hz, 1H), 4.32
(t, J = 6 Hz and J = 9 Hz , 1H), 8.11 (d, J = 9 Hz, 2H),
8.33 (d, J = 9 Hz, 2H), 8.84 (d, J = 6 Hz, 1H), 12.76
(brs, 1H).
MS m/z (ESI): 265 [(M-H)-], 267 [(M+H)
+],
Calculated; m/z 266.
1.00 (dd, J = 6 Hz and J = 9 Hz, 6H), 2.22 (m, J = 6 Hz and J = 9 Hz,
1H), 4.32 (t, J = 6 Hz and J = 9 Hz , 1H), 7.18 (dd, J = 3 Hz and J = 9
Hz, 1H), 7.95 (d, J = 9 Hz, 2H), 8.09 (d, J = 9 Hz, 2H), 8.14 (dd, J =
3 Hz and J = 9 Hz, 1H), 8.39 (d, J = 3 Hz, 1H), 8.64 (d, J = 6 Hz,
1H), 12.70 (brs, 1H).
MS m/z (ESI): 384 [(M-H)-], 386 [(M+H)
+], Calculated; m/z 385.
4 d 1.00 (dd, J = 6 Hz, 6H), 2.20 (m, J = 6 Hz, 1H), 4.32
(t, J = 6 Hz and J = 9 Hz , 1H), 8.11 (d, J = 9 Hz, 2H),
8.33 (d, J = 9 Hz, 2H), 8.84 (d, J = 6 Hz, 1H), 12.76
(brs, 1H).
MS m/z (ESI): 265 [(M-H)-], 267 [(M+H)
+],
Calculated; m/z 266.
0.99 (dd, J = 6.6 Hz, 6H), 2.23 (m, J = 6.6 Hz, 1H), 4.32 (t, J = 7.2
Hz and J = 7.8 Hz , 1H), 7.16 (d, J = 9 Hz, 1H), 7.94 (d, J = 8.4 Hz,
2H), 8.10 (d, J = 8.4 Hz, 2H), 8.13 (dd, J = 2.4 Hz and J = 8.4 Hz,
1H), 8.38 (d, J = 2.4 Hz, 1H), 8.64 (d, J = 8.1 Hz, 1H), 12.68 (brs,
1H).
MS m/z (ESI): 384 [(M-H)-], 386 [(M+H)
+], Calculated; m/z 385.
5 e 1.06 (s, 9H), 4.39 (d, J = 9 Hz, 1H), 8.08 (d, J = 9 Hz , 1.07 (s, 9H), 4.40 (d, J = 9 Hz, 1H), 7.17 (d, J = 8.7 Hz , 1H), 7.81 (d,
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 49
Chapter - I
2H), 8.32 (d, J = 9 Hz, 2H), 8.66 (d, J = 9 Hz, 1H),
12.83 (brs, 1H).
MS m/z (ESI): 279.1 [(M-H)-], 281.2 [(M+H)
+],
Calculated; m/z 280.
J = 8.4 Hz, 2H), 8.10 (d, J = 8.4 Hz, 2H), 8.13 (dd, J = 2.4 Hz and J =
6.6 Hz, 1H), 8.38 (d, J = 2.4 Hz, 1H), 12.72 (brs, 1H).
MS m/z (ESI): 398.1 [(M-H)-], 400.2 [(M+H)
+], Calculated; m/z 399.
6 f 3.05 (dd, J = 10.8 Hz and J = 3 Hz, 1H), 3.23 (dd, J =
4.2 Hz and J = 9.6 Hz, 1H), 4.64 (m, J = 1.5 Hz, J =
2.4 Hz and J = 4.5 Hz , 1H), 7.18 (m, J = 6.9 Hz and J
= 6.6 Hz , 1H), 7.29 (m, J = 6.9 Hz, J = 2.4 Hz and J =
7.8 Hz, 4H), 8.01 (d, J = 8.7 Hz, 2H), 8.30 (d, J = 8.7
Hz, 2H), 9.10 (d, J = 8.1 Hz, 1H), 12.85 (brs, 1H).
MS m/z (ESI): 313 [(M-H)-], 315 [(M+H)
+],
Calculated; m/z 314.
3.11 (dd, J = 10.8 Hz and J = 3 Hz, 1H), 3.23 (dd, J = 4.2 Hz and J =
9.6 Hz, 1H), 4.67 (m, J = 4.5 Hz, J = 6.3 Hz and J = 6.9 Hz , 1H),
7.17 (d, J = 9 Hz, 1H), 7.20 (m, J = 7.2 Hz, 1H), 7.30 (m, J = 7.5 Hz
and J = 7.8 Hz, 4H), 7.92 (d, J = 7.8 Hz, 2H), 8.00 (d, J = 8.4 Hz,
2H), 8.11 (dd, J = 8.7 Hz and J = 0.9 Hz , 1H), 8.37 (t, J = 0.9 Hz and
J = 1.5 Hz, 1H), 8.93 (d, J = 7.8 Hz, 1H), 12.26 (brs, 1H).
MS m/z (ESI): 432.1 [(M-H)-], Calculated; m/z 333.
7 g 6.03 (dd, J = 7.5 Hz, 1H), 7.40 (m, J = 4.5 Hz and J =
2.7 Hz, 2H), 7.55 (m, J = 4.5 Hz, J = 2.4 Hz and J =
2.7 Hz , 2H), 8.14 (d, J = 8.7 Hz, 2H), 8.33 (d, J = 9
Hz, 2H), 9.54 (d, J = 7.5 Hz, 1H), 13.18 (brs, 1H).
MS m/z (ESI): 333 [(M-H)-], Calculated; m/z 334.5.
6.07 (d, J = 6 Hz, 1H), 7.17 (d, J = 9 Hz, 1H), 7.41 (m, J = 6 Hz and J
= 3 Hz, 2H), 7.58 (m, J = 9 Hz and J = 3 Hz , 2H), 7.95 (d, J = 9 Hz,
2H), 8.12 (d, J = 9 Hz, 2H), 8.14 (d, J = 9 Hz and J = 3 Hz, 1H), 8.39
(d, J = 3 Hz, 1H), 9.36 (d, J = 6 Hz, 1H), 13.18 (brs, 2H).
MS m/z (ESI): 452.4 [(M-H)-], Calculated; m/z 453.5.
8 h 3.08 (m, J = 9.9 Hz and J = 3.9 Hz, 2H), 4.53 (m, J =
4.5 Hz and J = 4.2 Hz, 1H), 8.12 (d, J = 8.7 Hz, 2H),
8.35 (d, J = 8.7 Hz, 2H), 9.04 (d, J = 7.8 Hz, 1H).
MS m/z (ESI): 269.1 [(M-H)-], 271.2 [(M+H)
+],
Calculated; m/z 270.
3.12 (m, J = 9 Hz and J = 3.9 Hz, 2H), 4.54 (m, J = 5 Hz and J = 3
Hz, 1H), 7.19 (d, J = 9 Hz, 1H), 7.98 (d, J = 9 Hz, 2H), 8.14 (d, J = 9
Hz, 2H), 8.16 (dd, J = 9 Hz and J = 2.5 Hz, 1H), 8.40 (d, J = 2.5 Hz,
1H), 9.06 (d, J = 9 Hz, 1H).
MS m/z (ESI): 388 [(M-H)-], Calculated; m/z 389.
9 i 3.82 (d, J = 6 Hz, 2H), 4.51 (m, J = 6 Hz, J = 9 Hz and
J = 3 Hz, 1H), 8.14 (d, J = 9 Hz, 2H), 8.34 (d, J = 9
Hz, 2H), 8.87 (d, J = 9 Hz, 1H), 12.84 (brs, 1H).
MS m/z (ESI): 253 [(M-H)-], 255.1 [(M+H)
+],
3.84 (d, J = 6 Hz, 2H), 4.52 (m, J = 6 Hz, J = 9 Hz and J = 3 Hz, 1H),
7.19 (d, J = 9 Hz, 1H), 7.97 (d, J = 9 Hz, 2H), 8.12 (d, J = 9 Hz, 2H),
8.15 (dd, J = 9 Hz and J = 2.5 Hz, 1H), 8.39 (d, J = 2.5 Hz, 1H), 8.73
(d, J = 9 Hz, 1H), 12.22 (brs, 1H).
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 50
Chapter - I
Calculated; m/z 254. MS m/z (ESI): 372 [(M-H)-], Calculated; m/z 373.
10 j 2.46 (dd, J = 3.9 Hz, 1H), 2.77 (dd, J = 6 Hz, and J =
9.9 Hz, 1H), 4.54 (m, J = 3.9 Hz, J = 6 Hz and J = 7.5
Hz, 1H), 8.09 (d, J = 8.7 Hz, 2H), 8.33 (d, J = 9 Hz,
2H), 8.82 (d, J = 7.5 Hz, 1H).
MS m/z (ESI): 281.1 [(M-H)-], 283.1 [(M+H)
+],
Calculated; m/z 282.
2.74 (dd, J = 8.4 Hz and J = 8.1 Hz, 1H), 2.89 (dd, J = 5.7 Hz, and J =
10.8 Hz, 1H), 4.79 (m, J = 8.1 Hz and J = 5.7 Hz, 1H), 7.18 (d, J =
8.7 Hz, 1H), 7.96 (d, J = 8.4 Hz, 2H), 8.06 (d, J = 8.4 Hz, 2H), 8.13
(dd, J = 2.4 Hz and J = 6.3 Hz , 1H), 8.39 (d, J = 2.4 Hz, 1H), 8.96 (d,
J = 7.8 Hz, 1H), 11.13 (brs, 1H), 12.76 (brs, 2H).
MS m/z (ESI): 399.9 [(M-H)-], Calculated; m/z 401.
11 k 2.63 (m, J = 3 Hz, J = 6 Hz, J = 9 Hz and J = 12 Hz,
2H), 4.74 (m, J = 6 Hz and J = 9 Hz, 1H), 6.97 and
7.42 (d, J = 135 Hz, 2H), 8.08 (d, J = 9 Hz, 2H), 8.34
(d, J = 9 Hz, 2H), 9.05 (d, J = 6 Hz, 1H), 12.85 (brs,
1H).
MS m/z (ESI): 280.1 [(M-H)-], 282.2 [(M+H)
+],
Calculated; m/z 281.
2.69 (m, J = 6 Hz, J = 9 Hz and J = 12 Hz, 2H), 4.77 (m, J = 6 Hz and
J = 9 Hz, 1H), 6.99 and 7.49 (d, J = 150 Hz, 2H), 7.16 (d, J = 9 Hz,
1H), 7.95 (d, J = 9 Hz, 2H), 8.07 (d, J = 9 Hz, 2H), 8.14 (dd, J = 9 Hz
and J = 2.5 Hz, 1H), 8.38 (t, J = 2.5 Hz, 1H), 8.90 (d, J = 9 Hz, 1H),
12.50 (brs, 1H).
MS m/z (ESI): 399 [(M-H)-], Calculated; m/z 400.
12 l 1.85 (m, J = 6 Hz, 1H), 1.89 (m, J = 9 Hz, 1H), 1.94
(m, J = 3 Hz, 1H), 2.29 (m, J = 6 Hz and J = 9 Hz ,
1H), 3.46 (m, J = 3 Hz and J = 6 Hz , 1H), 3.61 (m, J =
9 Hz , 1H), 4.44 (m, J = 3 Hz and J = 6 Hz , 1H), 7.77
(d, J = 9 Hz, 2H), 8.30 (d, J = 9 Hz, 2H), 12.70 (brs,
1H).
MS m/z (ESI): 263.1 [(M-H)-], 265.1 [(M+H)
+],
Calculated; m/z 264.
1.91 (m, J = 6 Hz and J = 9 Hz, 3H), 2.30 (m, J = 6 Hz and J = 9 Hz,
1H), 3.58 (m, J = 3 Hz, J = 6 Hz and J = 9 Hz, 2H), 4.44 (m, J = 6 Hz
and J = 3 Hz , 1H), 7.17 (d, J = 9 Hz, 1H), 7.73 (d, J = 9 Hz , 2H),
7.93 (d, J = 9 Hz, 2H), 8.11 (dd, J = 3 Hz, 1H), 8.37 (d, J = 1.5 Hz,
1H), 12.60 (brs, 1H).
MS m/z (ESI): 382.1 [(M-H)-], Calculated; m/z 383.
13 m 1.99 (m, J = 3 Hz and J = 6 Hz, 1H), 2.26 (m, J = 9 Hz
and J = 12 Hz, 1H), 3.25 (m, J = 12 Hz, 1H), 3.70 (m,
J = 3 Hz, J = 6 Hz and J = 24 Hz , 1H), 4.31 (m, 1H),
4.54 (m, J = 9 Hz , 1H), 7.80 (d, J = 9 Hz, 2H), 8.32
(d, J = 9 Hz, 2H).
1.99 (m, J = 3 Hz and J = 6 Hz, 1H), 2.25 (m, J = 9 Hz and J = 12 Hz,
1H), 3.34 (m, J = 9 Hz, 1H), 3.79 (m, J = 3 Hz and J = 6 Hz , 1H),
4.31 (m, J = 6 Hz, 1H), 4.54 (m, J = 9 Hz , 1H), 7.18 (d, J = 9 Hz,
1H), 7.74 (d, J = 9 Hz, 2H), 7.96 (d, J = 9 Hz, 2H), 8.12 (dd, J = 3 Hz
and J = 9 Hz, 1H), 8.38 (dd, J = 3 Hz, 1H), 12.10 (brs,1H).
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 51
Chapter - I
MS m/z (ESI): 279.1 [(M-H)-], 281.2 [(M+H)
+],
Calculated; m/z 280.
MS m/z (ESI): 398.1 [(M-H)-], Calculated; m/z 399.
14 n 1.97 (m, J = 3 Hz and J = 6 Hz, 1H), 2.12 (m, J = 6 Hz
and J = 9 Hz, 1H), 2.39 (m, J = 6 Hz and J = 9 Hz,
2H), 4.44 (m, J = 3 Hz, 1H), 8.11 (d, J = 9 Hz , 2H),
8.33 (d, J = 9 Hz , 2H), 9.00 (d, J = 6 Hz, 1H), 12.59
(brs, 1H).
MS m/z (ESI): 295.1 [(M-H)-], 297.2 [(M+H)
+],
Calculated; m/z 296.
2.00 (m, J = 5.4 Hz and J = 9.3 Hz, 1H), 2.12 (m, J = 6 Hz and J =
7.8 Hz, 1H), 2.40 (t, J = 7.2 Hz, 2H), 4.44 (m, J = 3 Hz and J = 9.6
Hz, 1H), 7.17 (d, J = 9 Hz, 1H), 7.95 (d, J = 9 Hz, 2H), 8.10 (d, J = 9
Hz, 2H), 8.13 (dd, J = 9 Hz and J = 2.4 Hz, 1H), 8.38 (d, J = 2.4 Hz ,
1H), 8.83 (d, J = 7.5 Hz, 1H), 12.20 (brs, 1H).
MS m/z (ESI): 414 [(M-H)-], Calculated; m/z 415.
15 o 2.54 (t, 2H), 3.48 (m, 2H), 8.06 (d, J = 8.5 Hz, 2H),
8.32 (d, J = 8.5 Hz, 2H), 8.89 (t, J = 5.5 Hz, 1H),
12.28 (brs, 1H).
MS m/z (ESI): 237 [(M-H)-], Calculated; m/z 238.
2.54 (t, 2H), 3.50 (m, 2H), 6.95 (d, J = 8.8 Hz, 1H), 7.87 (d, J = 8.5
Hz, 2H), 8.02 (d, J = 8.5 Hz, 2H), 7.95 (dd, J = 8.8 Hz and 2.5 Hz,
1H), 8.34 (d, J = 2.5 Hz, 1H), 8.68 (t, J = 5.5 Hz, 1H), 12.12 (brs,
1H).
MS m/z (ESI): 356 [(M-H)-], Calculated; m/z 357.
16 p 1.37-1.50 (m, J = 9 Hz and J = 12 Hz, 10H), 2.31 (s,
2H), 3.44 (d, J = 6 Hz, 2H), 8.07 (d, J = 9 Hz, 2H),
8.32 (d, J = 9 Hz , 2H), 8.58 (t, J = 6 Hz , 1H), 12.11
(brs, 1H).
MS m/z (ESI): 319.1 [(M-H)-], 321.2 [(M+H)
+],
Calculated; m/z 320.
1.37-1.50 (m, J = 9 Hz and J = 7.2 Hz, 10H), 2.33 (s, 2H), 3.44 (d, J =
5.7 Hz, 2H), 7.08 (d, J = 8.7 Hz, 1H), 7.92 (d, J = 8.4 Hz, 2H), 8.03
(d, J = 8.7 Hz, 2H), 8.06 (d, J = 8.4 Hz, 1H), 8.37 (d, J = 2.4 Hz ,
1H), 8.43 (t, J = 5.7 Hz , 1H), 11.94 (brs, 1H).
MS m/z (ESI): 438.1 [(M-H)-], Calculated; m/z 439.
17 q 0.87 (dd, J = 2.7 Hz and J = 6.6 Hz, 6H), 1.15 (m, J =
6.6 Hz and J = 6.9 Hz, 2H), 1.70 (m, J = 6 Hz, 1H),
2.16 (m, J = 12.9 Hz, 1H), 2.11 (m, J = 6.6 Hz, 1H),
2.32 (m, J = 7.8 Hz , 1H), 3.33 (m, J = 7.8 Hz, 1H),
3.38 (m, J = 7.8 Hz, 1H), 8.07 (d, J = 8.7 Hz, 2H), 8.33
(d, J = 8.7 Hz, 2H), 8.81 (t, J = 5.7 Hz, 1H), 12.12 (brs,
1H).
0.89 (dd, J = 2.7 Hz and J = 6.6 Hz, 6H), 1.16 (m, J = 6 Hz and J = 9
Hz, 2H), 1.71 (m, J = 6 Hz, 1H), 2.10 (m, J = 6 Hz, 1H), 2.15 (m, J =
9 Hz and J = 3 Hz, 1H), 2.33 (m, J = 9 Hz and J = 3 Hz , 1H), 3.17
(m, J = 6 Hz, 1H), 3.34 (m, J = 6 Hz, 1H), 7.19 (d, J = 8.7 Hz, 1H),
7.93 (d, J = 8.7 Hz, 2H), 8.03 (d, J = 8.7 Hz, 2H), 8.12 (dd, J = 9 Hz
and J = 3 Hz , 1H), 8.38 (d, J = 3 Hz, 1H), 8.66 (t, J = 6 Hz and J = 3
Hz, 1H), 12.03 (brs, 1H).
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 52
Chapter - I
MS m/z (ESI): 307.2 [(M-H)-], 308.9 [(M+H)
+],
Calculated; m/z 308.
MS m/z (ESI): 426.2 [(M-H)-], Calculated; m/z 427.
18 r 0.87 (dd, J = 2.7 Hz and J = 6.6 Hz, 6H), 1.15 (m, J =
6.6 Hz and J = 6.9 Hz, 2H), 1.70 (m, J = 6 Hz, 1H),
2.16 (m, J = 12.9 Hz, 1H), 2.11 (m, J = 6.6 Hz, 1H),
2.32 (m, J = 7.8 Hz , 1H), 3.33 (m, J = 7.8 Hz, 1H),
3.38 (m, J = 7.8 Hz, 1H), 8.07 (d, J = 8.7 Hz, 2H), 8.33
(d, J = 8.7 Hz, 2H), 8.81 (t, J = 5.7 Hz, 1H), 12.12
(brs, 1H).
MS m/z (ESI): 307.2 [(M-H)-], 308.9 [(M+H)
+],
Calculated; m/z 308.
0.89 (dd, J = 2.7 Hz and J = 6.6 Hz, 6H), 1.16 (m, J = 6 Hz and J = 9
Hz, 2H), 1.71 (m, J = 6 Hz, 1H), 2.10 (m, J = 6 Hz, 1H), 2.15 (m, J =
9 Hz and J = 3 Hz, 1H), 2.33 (m, J = 9 Hz and J = 3 Hz , 1H), 3.17
(m, J = 6 Hz, 1H), 3.34 (m, J = 6 Hz, 1H), 7.19 (d, J = 8.7 Hz, 1H),
7.93 (d, J = 8.7 Hz, 2H), 8.03 (d, J = 8.7 Hz, 2H), 8.12 (dd, J = 9 Hz
and J = 3 Hz , 1H), 8.38 (d, J = 3 Hz, 1H), 8.66 (t, J = 6 Hz and J = 3
Hz, 1H), 12.03 (brs, 1H).
MS m/z (ESI): 426.2 [(M-H)-], Calculated; m/z 427.
19 s 0.87 (m, J = 2.7 Hz, J = 3.9 Hz, J = 5.1 Hz, J = 6.6 Hz
and J = 7.5 Hz, 6H), 1.18 (m, 1H), 1.40 (m, 1H), 1.48
(m, J = 2.7 Hz and J = 3.9 Hz, 1H), 2.21 (m, 1H), 2.23
(m, J = 3.3 Hz, J = 4.5 Hz, J = 5.1 Hz and J = 8.1 Hz ,
2H), 3.13 (m, 1H), 3.38 (m, 1H), 8.07 (d, J = 8.7 Hz,
2H), 8.33 (d, J = 8.7 Hz, 2H), 8.83 (t, J = 5.1 Hz, 1H),
12.13 (brs, 1H).
MS m/z (ESI): 307.2 [(M-H)-], 308.9 [(M+H)
+],
Calculated; m/z 308.
0.87 (m, J = 2.7 Hz, J = 3.9 Hz, J = 5.1 Hz, J = 6.6 Hz and J = 7.5
Hz, 6H), 1.20 (m, 1H), 1.35 (m, 1H), 1.48 (m, J = 2.7 Hz and J = 3.9
Hz, 1H), 2.15 (m, 1H), 2.22 (m, J = 3.3 Hz, J = 4.5 Hz, J = 5.1 Hz
and J = 8.1 Hz , 2H), 3.18 (m, 1H), 3.36 (m, 1H), 7.18 (d, J = 8.7 Hz,
1H), 7.94 (d, J = 8.7 Hz, 2H), 8.03 (d, J = 8.7 Hz, 2H), 8.13 (dd, J =
8.7 Hz and J = 2.4 Hz , 1H), 8.37 (d, J = 2.4 Hz, 1H),8.61 (d, J = 5.1
Hz, 1H), 12.10 (brs, 1H).
MS m/z (ESI): 426.2 [(M-H)-], Calculated; m/z 427.
20 t 0.88 (t, J = 9 Hz, 3H), 1.28 (m, J = 12 Hz, 6H), 2.09
(m, 1H), 2.17 (m, J = 9 Hz and J = 15 Hz, 1H), 2.31
(m, J = 3 Hz and J = 12 Hz, 1H), 3.20 (m, J = 6 Hz,
1H), 3.35 (m, J = 6 Hz, 1H), 8.07 (d, J = 8 Hz, 2H),
8.33 (d, J = 8 Hz, 2H), 8.80 (t, J = 6 Hz, 1H), 12.24
(brs, 1H).
MS m/z (ESI): 307.2 [(M-H)-], 308.9 [(M+H)
+],
Calculated; m/z 308.
0.88 (t, J = 6.6 Hz, 3H), 1.30 (m, J = 12 Hz, 6H), 2.09 (m, 1H), 2.18
(m, J = 7.2 Hz and J = 15 Hz, 1H), 2.34 (m, J = 5.4 Hz and J = 9.6
Hz, 1H), 3.19 (m, J = 5.1 Hz, 1H), 3.36 (m, J = 6 Hz, 1H), 7.16 (d, J
= 9 Hz, 1H), 7.93 (d, J = 8.4 Hz, 2H), 8.03 (d, J = 8.4 Hz, 2H), 8.12
(dd, J = 5.7 Hz and J = 2.4 Hz, 1H), 8.37 (d, J = 2.4 Hz, 1H), 8.63 (t,
J = 5.5 Hz, 1H), 12.21 (brs, 1H).
MS m/z (ESI): 426.2 [(M-H)-], Calculated; m/z 427.
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Studies on the synthesis of anti-inflammatory drug, Balsalazide 53
Chapter - I
Table-1.14
S. No. COMPOUND 37
1 a 3.68 (s, 3H), 3.94 (s, 3H), 4.05 (d, J = 6 Hz, 2H), 7.21 (d, J = 8.7 Hz, 1H), 7.95 (d, J = 9 Hz, 2H), 8.08 (d, J = 9 Hz, 2H), 8.12 (dd,
J = 3 Hz and J = 9 Hz, 1H), 8.35 (d, J = 3 Hz, 1H), 9.15 (t, J = 6 Hz, 1H), 11.06 (brs, 1H).
MS m/z (ESI): 370.1 [(M-H)-], Calculated; m/z 371.
2 b 1.44 (d, J = 6 Hz, 3H), 3.67 (s, 3H), 3.94 (s, 3H), 4.53 (m, J = 9 Hz and J = 6 Hz, 1H), 7.21 (d, J = 9 Hz, 1H), 7.96 (d, J = 9 Hz,
2H), 8.11 (d, J = 9 Hz, 2H), 8.14 (d, J = 3 Hz and J = 9 Hz, 1H), 8.36 (d, J = 3 Hz, 1H), 8.98 (d, J = 9 Hz, 1H), 11.05 (brs, 2H).
MS m/z (ESI): 384.1 [(M-H)-], 386 [(M+H)
+], Calculated; m/z 385.
3 c 1.00 (dd, J = 6 Hz and J = 9 Hz, 6H), 2.22 (m, J = 6 Hz and J = 9 Hz, 1H), 3.68 (s,3H), 3.94 (s, 3H), 4.33 (t, J = 6 Hz and J = 9 Hz
, 1H), 7.21 (dd, J = 3 Hz and J = 9 Hz, 1H), 7.95 (d, J = 9 Hz, 2H), 8.10 (d, J = 9 Hz, 2H), 8.14 (dd, J = 3 Hz and J = 9 Hz, 1H),
8.35 (d, J = 3 Hz, 1H), 8.80 (d, J = 6 Hz, 1H), 11.06 (brs, 1H).
MS m/z (ESI): 412 [(M-H)-], Calculated; m/z 413.
4 d 0.99 (dd, J = 6.6 Hz, 6H), 2.23 (m, J = 6.6 Hz, 1H), 3.68 (s,3H), 3.94 (s, 3H), 4.33 (t, J = 7.2 Hz and J = 7.8 Hz , 1H), 7.16 (d, J =
9 Hz, 1H), 7.94 (d, J = 8.4 Hz, 2H), 8.10 (d, J = 8.4 Hz, 2H), 8.13 (dd, J = 2.4 Hz and J = 8.4 Hz, 1H), 8.35 (d, J = 2.4 Hz, 1H),
8.80 (d, J = 8.1 Hz, 1H), 11.06 (brs, 1H).
MS m/z (ESI): 412 [(M-H)-], Calculated; m/z 413.
5 e 1.05 (s, 9H), 3.68 (s, 3H), 3.94 (s, 3H), 4.46 (d, J = 6 Hz, 1H), 7.22 (d, J = 8.7 Hz , 1H), 7.87 (d, J = 8.4 Hz, 2H), 7.99 (d, J = 8.4
Hz, 2H), 8.13 (dd, J = 2.4 Hz and J = 6.6 Hz, 1H), 8.34 (d, J = 2.4 Hz, 1H), 8.57 (d, J = 5.4 Hz, 1H), 11.06 (brs, 1H).
MS m/z (ESI): 426.1 [(M-H)-], Calculated; m/z 427.
6 f 3.17 (m, J = 10.8 Hz and J = 3 Hz, 2H), 3.66 (s, 3H), 3.94 (s, 3H), 4.70 (m, J = 6.3 Hz and J = 9.1 Hz , 1H), 7.20 (d, J = 9 Hz,
1H), 7.29 (m, J = 7.5 Hz and J = 7.8 Hz, 5H), 7.92 (d, J = 8.5 Hz, 2H), 8.00 (d, J = 8.4 Hz, 2H), 8.11 (dd, J = 8.7 Hz and J = 0.9
Hz , 1H), 8.33 (t, J = 0.9 Hz and J = 1.5 Hz, 1H), 9.06 (d, J = 7.8 Hz, 1H), 10.94 (brs, 1H).
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Chapter - I
MS m/z (ESI): 360 [(M-H)-], Calculated; m/z 361.
7 g 3.73 (s, 3H), 3.94 (s, 3H), 6.11 (d, J = 6 Hz, 1H), 7.19 (d, J = 9 Hz, 1H), 7.42 (m, J = 6 Hz and J = 3 Hz, 2H), 7.53 (m, J = 9 Hz
and J = 3 Hz , 2H), 7.95 (d, J = 9 Hz, 2H), 8.12 (d, J = 9 Hz, 2H), 8.14 (d, J = 9 Hz and J = 3 Hz, 1H), 8.34 (d, J = 3 Hz, 1H), 9.49
(d, J = 6 Hz, 1H), 10.56 (brs, 1H).
MS m/z (ESI): 480.4 [(M-H)-], Calculated; m/z 481.5.
8 j 2.86 (dd, J = 8.4 Hz and J = 8.1 Hz, 1H), 2.98 (dd, J = 5.7 Hz, and J = 10.8 Hz, 1H), 3.64 (s, 3H), 3.67 (s, 3H), 3.94 (s, 3H), 4.88
(m, J = 8.1 Hz and J = 5.7 Hz, 1H), 7.21 (d, J = 8.7 Hz, 1H), 7.96 (d, J = 8.4 Hz, 2H), 8.06 (d, J = 8.4 Hz, 2H), 8.14 (dd, J = 2.4
Hz and J = 6.3 Hz , 1H), 8.34 (d, J = 2.4 Hz, 1H), 9.12 (d, J = 7.8 Hz, 1H), 11.04 (brs, 1H).
MS m/z (ESI): 442.1 [(M-H)-], Calculated; m/z 443.
9 k 2.69 (m, J = 6 Hz, J = 9 Hz and J = 12 Hz, 2H), 3.67 (s,3H), 3.96 (s,3H), 4.89 (m, J = 6 Hz and J = 9 Hz, 1H), 6.99 and 7.49 (d, J
= 150 Hz, 2H), 7.18 (d, J = 9 Hz, 1H), 7.95 (d, J = 9 Hz, 2H), 8.07 (d, J = 9 Hz, 2H), 8.14 (dd, J = 9 Hz and J = 2.5 Hz, 1H), 8.38
(t, J = 2.5 Hz, 1H), 8.85 (d, J = 9 Hz, 1H), 12.50 (brs, 1H).
MS m/z (ESI): 427 [(M-H)-], Calculated; m/z 428.
10 l 1.92 (m, J = 6 Hz and J = 9 Hz, 3H), 2.30 (m, J = 6 Hz and J = 9 Hz, 1H), 3.58 (m, J = 3 Hz, J = 6 Hz and J = 9 Hz, 2H), 3.70 (s,
3H), 3.94 (s, 3H), 4.52 (m, J = 6 Hz and J = 3 Hz , 1H), 7.20 (d, J = 9 Hz, 1H), 7.73 (d, J = 9 Hz , 2H), 7.93 (d, J = 9 Hz, 2H), 8.10
(dd, J = 3 Hz, 1H), 8.33 (d, J = 1.5 Hz, 1H), 11.03 (brs, 1H).
MS m/z (ESI): 406.1 [(M-H)-], Calculated; m/z 407.
11 m 2.03 (m, J = 3 Hz and J = 6 Hz, 1H), 2.23 (m, J = 9 Hz and J = 12 Hz, 1H), 3.69 (s,3H), 3.80 (m, J = 3 Hz and J = 6 Hz , 1H), 3.94
(s, 3H), 4.32 (m, J = 6 Hz, 1H), 4.61 (m, J = 9 Hz , 1H), 5.16 (d, J = 3 Hz , 1H), 7.21 (d, J = 9 Hz, 1H), 7.74 (d, J = 9 Hz, 2H),
7.96 (d, J = 9 Hz, 2H), 8.12 (dd, J = 3 Hz and J = 9 Hz, 1H), 8.34 (dd, J = 3 Hz, 1H), 11.05 (brs,1H).
MS m/z (ESI): 426.1 [(M-H)-], Calculated; m/z 427.
12 n 2.05 (m, J = 5.4 Hz and J = 9.3 Hz, 1H), 2.14 (m, J = 6 Hz and J = 7.8 Hz, 1H), 2.47 (t, J = 7.2 Hz, 2H), 3.60 (s, 3H), 3.67 (s, 3H),
3.94 (s, 3H), 4.50 (m, J = 3 Hz and J = 9.6 Hz, 1H), 7.20 (d, J = 9 Hz, 1H), 7.97 (d, J = 9 Hz, 2H), 8.09 (d, J = 9 Hz, 2H), 8.14
(dd, J = 9 Hz and J = 2.4 Hz, 1H), 8.36 (d, J = 2.4 Hz , 1H), 8.95 (d, J = 6 Hz, 1H), 11.06 (brs, 1H).
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Chapter - I
MS m/z (ESI): 456 [(M-H)-], Calculated; m/z 457.
13 o 2.63 (t, J = 6 Hz, 2H), 3.52 (m, J = 6 Hz, 2H), 3.62 (s, 3H), 3.94 (s, 3H), 7.20 (d, J = 8.8 Hz, 1H), 7.92 (d, J = 8.5 Hz, 2H), 8.03
(d, J = 8.5 Hz, 2H), 8.12 (dd, J = 8.8 Hz and 2.5 Hz, 1H), 8.33 (d, J = 2.5 Hz, 1H), 8.74 (t, J = 5.5 Hz, 1H), 11.01 (brs, 1H).
MS m/z (ESI): 384 [(M-H)-], Calculated; m/z 385.
14 p 1.37-1.50 (m, 10H), 2.40 (s, 2H), 3.42 (d, J = 5.7 Hz, 2H), 3.58 (s, 3H), 3.94 (s, 3H), 7.20 (d, J = 8.7 Hz, 1H), 7.92 (d, J = 8.4 Hz,
2H), 8.03 (d, J = 8.7 Hz, 2H), 8.12 (d, J = 8.4 Hz, 1H), 8.33 (d, J = 2.4 Hz , 1H), 8.37 (t, J = 5.7 Hz , 1H), 11.01 (brs, 1H).
MS m/z (ESI): 466.1 [(M-H)-], Calculated; m/z 467.
15 q 0.87 (dd, J = 2.7 Hz and J = 6.6 Hz, 6H), 1.16 (m, J = 6 Hz and J = 9 Hz, 2H), 1.68 (m, J = 6 Hz, 1H), 2.21 (m, J = 6 Hz, 2H),
2.42 (m, J = 9 Hz and J = 3 Hz, 1H), 3.17 (m, J = 6 Hz, 1H), 3.34 (m, J = 6 Hz, 1H), 3.54 (s, 3H), 3.94 (s, 3H), 7.21 (d, J = 8.7 Hz,
1H), 7.93 (d, J = 8.7 Hz, 2H), 8.03 (d, J = 8.7 Hz, 2H), 8.12 (dd, J = 9 Hz and J = 3 Hz , 1H), 8.34 (d, J = 3 Hz, 1H), 8.66 (t, J = 6
Hz and J = 3 Hz, 1H), 11.05 (brs, 1H).
MS m/z (ESI): 454.2 [(M-H)-], Calculated; m/z 455.
16 r 0.88 (dd, J = 2.7 Hz and J = 6.6 Hz, 6H), 1.16 (m, J = 6 Hz and J = 9 Hz, 2H), 1.69 (m, J = 6 Hz, 1H), 2.24 (m, J = 6 Hz, 2H),
2.40 (m, J = 9 Hz and J = 3 Hz, 1H), 3.18 (m, J = 6 Hz, 1H), 3.34 (m, J = 6 Hz, 1H), 3.56 (s, 3H), 3.94 (s, 3H), 7.20 (d, J = 8.7 Hz,
1H), 7.94 (d, J = 8.7 Hz, 2H), 8.03 (d, J = 8.7 Hz, 2H), 8.11 (dd, J = 9 Hz and J = 3 Hz , 1H), 8.32 (d, J = 3 Hz, 1H), 8.66 (t, J = 6
Hz and J = 3 Hz, 1H), 11.06 (brs, 1H).
MS m/z (ESI): 454.2 [(M-H)-], Calculated; m/z 455.
17 s 0.87 (m, J = 2.7 Hz, J = 3.9 Hz, J = 5.1 Hz, J = 6.6 Hz and J = 7.5 Hz, 6H), 1.17 (m, 1H), 1.35 (m, 1H), 1.48 (m, J = 2.7 Hz and J
= 3.9 Hz, 1H), 2.26 (m, 1H), 2.32 (m, J = 3.3 Hz, J = 4.5 Hz, J = 5.1 Hz and J = 8.1 Hz , 2H), 3.18 (m, 1H), 3.36 (m, 1H), 3.52 (s,
3H), 3.94 (s, 3H), 7.21 (d, J = 8.7 Hz, 1H), 7.93 (d, J = 8.7 Hz, 2H), 8.03 (d, J = 8.7 Hz, 2H), 8.13 (dd, J = 8.7 Hz and J = 2.4 Hz ,
1H), 8.34 (d, J = 2.4 Hz, 1H),8.62 (d, J = 5.1 Hz, 1H), 11.06 (brs, 1H).
MS m/z (ESI): 454.2 [(M-H)-], Calculated; m/z 455.
18 t 0.88 (t, J = 6.6 Hz, 3H), 1.30 (m, J = 12 Hz, 6H), 2.14 (m, 1H), 2.25 (m, J = 7.2 Hz and J = 15 Hz, 1H), 2.43 (m, J = 5.4 Hz and J
= 9.6 Hz, 1H), 3.19 (m, J = 5.1 Hz, 1H), 3.34 (m, J = 6 Hz, 1H), 3.57 (s, 3H), 3.95 (s, 3H), 7.20 (d, J = 9 Hz, 1H), 7.90 (d, J = 8.4
Hz, 2H), 8.06 (d, J = 8.4 Hz, 2H), 8.12 (dd, J = 5.7 Hz and J = 2.4 Hz, 1H), 8.32 (d, J = 2.4 Hz, 1H), 8.65 (t, J = 5.5 Hz, 1H),
MD. UMAR KHAN Thesis
Studies on the synthesis of anti-inflammatory drug, Balsalazide 56
Chapter - I
11.07 (brs, 1H).
MS m/z (ESI): 454.2 [(M-H)-], Calculated; m/z 455.
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Chapter - I
SPECTRA:
…..IR SPECTRUM OF COMPOUND 7
…..1H NMR SPECTRUM OF COMPOUND 7 IN DMSO-d6
…..MASS SPECTRUM OF COMPOUND 7
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…..IR SPECTRUM OF COMPOUND 8
…..1H NMR SPECTRUM OF COMPOUND 8 IN DMSO-d6
…..MASS SPECTRUM OF COMPOUND 8
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Chapter - I
…..IR, 1H NMR,
13C NMR AND MASS SPECTRUM OF COMPOUND 1
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Chapter - I
…..IR SPECTRUM OF COMPOUND 13
…..1H NMR SPECTRUM OF COMPOUND 13 IN DMSO-d6
…..13
C NMR SPECTRUM OF COMPOUND 13 IN DMSO-d6
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Chapter - I
…..1H NMR SPECTRUM OF COMPOUND 14 IN DMSO-d6
…..13
C NMR SPECTRUM OF COMPOUND 14 IN DMSO-d6
…..IR SPECTRUM OF COMPOUND 15
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…..1H NMR SPECTRUM OF COMPOUND 15 IN DMSO-d6
…..13
C NMR SPECTRUM OF COMPOUND 15 IN DMSO-d6
…..MASS SPECTRUM OF COMPOUND 15
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Chapter - I
…..IR, 1H NMR,
13C NMR AND MASS SPECTRUM OF COMPOUND 16
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Chapter - I
…..IR, 1H NMR AND
13C NMR SPECTRUM OF COMPOUND 17
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Chapter - I
….. 1H NMR,
13C NMR AND MASS SPECTRUM OF COMPOUND 18
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…..IR, 1H NMR,
13C NMR AND MASS SPECTRUM OF COMPOUND 19
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…..IR, 1H NMR AND
13C NMR SPECTRUM OF COMPOUND 20
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…..IR, 1H NMR AND
MASS SPECTRUM OF COMPOUND N-Ac-8
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Chapter - I
…..IR, 1H NMR AND
MASS SPECTRUM OF COMPOUND N-Ac-2
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….. 1H NMR SPECTRUM OF COMPOUND 25
….. MASS SPECTRUM OF COMPOUND 25
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Chapter - I
….. 1H NMR SPECTRUM OF COMPOUND 26
….. MASS SPECTRUM OF COMPOUND 26
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Chapter - I
….. 1H NMR SPECTRUM OF COMPOUND 32
….. 1H NMR AND MASS SPECTRUM OF COMPOUND 33
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….. 1H NMR SPECTRUM OF COMPOUND 37
….. MASS SPECTRUM OF COMPOUND 37
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….. 1H NMR AND MASS SPECTRUM OF COMPOUND 43 AND 44
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…..IR, 1H NMR AND MASS SPECTRUM OF COMPOUND 47
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…..IR, 1H NMR AND MASS SPECTRUM OF COMPOUND 49
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Chapter - I
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