synthesis tetrahydroisoquinoline-based peptidomimetics mimicking reverse turn secondary structures...
TRANSCRIPT
Synthesis
NH2
MeO
MeO
NH
O
MeNH
MeO
MeO
NH
O
Me
O
CbzHN COOMe
H
N
MeO
MeO O
NH
O
Me
H1
NHCbz
5% TFA, DCM 1.Toluene, Reflux
2. Chromatographic Separation
1. H2, Pd/C
2. Ac2O, py
(35%) (86%)
1
N
MeO
MeO O
NH
O
Me
H1
NHCbz(38%) (82%)
H3
H3
NHCbz
COOMe
N
MeO
MeO O
NH
O
Me
H1
NHAc
N
MeO
MeO O
NH
O
Me
H1
NHAc
H3
H3
H10
H10
TETRAHYDROISOQUINOLINE-BASED PEPTIDOMIMETICS MIMICKING REVERSE TURN SECONDARY STRUCTURES
Nicola Landoni, Giordano Lesma, Alessandro Sacchetti and Alessandra Silvani
Dipartimento di Chimica Organica e Industriale, Università degli Studi di Milano, via Venezian 21 – 20133 Milano, Italy E-mail: [email protected]
The Tic heterocyclic frame (Tic = 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid) is present in many biologically active natural alkaloids and in a great number of pharmaceutical compounds. Particularly, the presence of the Tic nucleus, which is a conformationally constrained Phe analogue, seems to be essential in many synthetic peptidomimetics showing agonistic and antagonistic activity towards many G protein-coupled receptors.
This project is aimed to identify new Tic-based privileged structures having the capability to mimic reverse turn secondary motifs.
MeO
MeON
O
NH
Me
O
HN
H
MeO
MeON
O
NH
Me
O
HN
H
O
O
N
NO
O
H
H
O
NH
Me
N
OH
O
R1
R2
R3
R4
R5
Conformational analysis (intramolecolar hydrogen bond evaluation):
- 1H NMR;- IR;- CD.
Peptidomimetics synthesis:
- Control of stereochemistry .
Peptidomimetics design through computational chemistry:
- Conformational analysis (MM / MC);- Analysis of geometrical parameters of low energy conformers.
Pyrrolo-tetrahydroisoquinoline (AHPIC)(AHPIC = 2-amino-8,9-dimethoxy-3-oxo-1,2,3,5,6,10b-hexahydro-pyrrolo[2,1-a]isoquinoline-5-carboxylic acid)
Conformational analysis of the structures AHPIC (Spartan ‘06, MC search, MMFF94 force field):
No. of conf. < 6
kcal/mol
% dα < 7Å
% β < 30°
% HA bond % HB bond
1 50 64 (32) 52 (26) 12 (6) 34 (17)
2 47 45 (21) 83 (39) 4 (2) 38 (18)Results expressed as % of the conformers that meet the requirement. In parentheses, the number of conformers.
MeO
MeON
O
N
1HN
O
3
HO
H
A
BMeO
MeON
O
N
1HN
O
3
HO
H
A
B
-turn typeConf. n° I I’ II II’ III III’
1 1 0.88 0.84 0.82 0.97 0.86 0.83
21 0.72 0.66 0.71 0.75 0.71 0.67
15 0.86 0.85 0.78 0.97 0.86 0.82
Similarity analysis of Ac-AHPIC-NHMe 1 and 2 with standard type β-turns.
The score is defined as [(1-R2)/N], where R2 is the r.m.s. of the distances between points of similarity of structures and N is the number of centres.
δ (ppm)b Δδ/ΔT (ppb/K)c IR (cm-1)
1NHMeNHAc
7.516.52
- 4.5- 5.5
3453, 3352
2NHMeNHAc
6.906.29
- 4.4- 4.0
3458, 3370
a All analyses were performed on 3.0 mM CDCl3 solutions. b At 298 K. c Determined between 298 and 328 K.
•NMR and IR spectroscopical data. a
MeO
MeON
O
N
1
HN
O
3
HO
H
A
BMeO
MeON
O
N
1
HN
O
3
HO
H
A
B
The presence of a reverse turn was observed in both the structures, with the C1 stereochemistry playing a central role in determining stable conformations. In particular, all the analyses led to the conclusion that a type II’ -turn is mostly stabilized in tetrapeptide mimic 1, while a typical inverse γ-turn geometry is revealed for the diastereoisomer 2.
Synthesis of a II’-turn mimic fragment of HOE 140.
BRADIKININ (BK): an endogenous ligand for G protein-coupled receptors (GPCRs):
GPCRs: membrane receptors involved in signal transduction;Control of different aspects of cell function, through the
mediation of the response to different extracellular stimuli;Adjust many biological processes, including sensory (smell,
taste, sight) and not sensory (appetite, digestion, blood pressure, reproduction, inflammation) activities;
Approximately 50% of drugs on the market today exerts its therapeutic function through interaction with the GPCRs.
NH
ON
HON
COOH
NH
NH
H2N
O
H-(D)-Arg-Arg-Pro-Hyp-Gly-Thi
H
O
N
H H
Ser6
D-Tic7
Oic8
Arg9
BRADIKININ (BK): H-Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9-OH
NH
ON
HO
O HN
N OH
O
HN NH
NH2
O
Ser6
Pro7Phe8
Arg9
H -turn (type II’)
Receptors (GCPRs) FunctionConcerned Pathologies
B2 receptors
(physiologically expressed)
Mediators of physiological action of BK (eg vasodilatation)
Bronchial asthma, allergic rhinitis, hypertension
B1 receptors
(overexpressed in case of trauma or infection)
Mediators of BK action during pathologies (eg
prostaglandin synthesis)
Chronic pain, inflammation
Spyro-pyrrolo-tetrahydroisoquinoline (SIPP)(SIPP = 2-(2'-oxo-2,4-dihydro-1H-spiro[isoquinoline-3,3'-pyrrolidine]-1'-yl)propanoic acid)
HOE 140: A powerful antagonist for the bradykinin B2 receptor
Type II’ -turn with D-Tic in the i+1 position.
(1) Boc-O-benzyl-L-serine,BOP-Cl, CH2Cl2, TEA
NH
N
CO2MeO
N
N
CO2MeO
OOBn
NHBoc
N
NO
OOBn
NHBoc
NH
O COOMe
(1) LiOH, THF, 0°C(2) N-Nitro-L-arginine methyl ester hydrochloride,BOP-Cl, CH2Cl2, TEA
MeNH2 8M in EtOH
33%
35% 97%
HN N
NH2
NO2
N
NO
OOBn
NHBoc
NH
O CONHMe HN N
NH2
NO2
δ (ppm) Δδ/ΔT (ppb/K) IR (cm-1)
NHMe n.d. n.d. 3323, 3435
•NMR and IR spectroscopical data.
CD (MeOH 0.2 mM)
Type II’ -turn
Biochemistry, 1978, 17, 4951.
Synthesis
N O
NO NHMe
O
n
n = 0, 1, 2, 3
% of conformers which meet the requirements.
NH2
COOH
(1) NaOH, H2O, EtOH(2) t-BuCHO, CH2Cl2, Reflux
(3) CbzCl, CH2Cl2, DMAP, 0°C
NO
Cbz
H O
NO
Cbz
O
KHMDS -78°C
Br
(45%) (86%) (99%)(4) F.C.
NO
Cbz
O
O
HO3, CH2Cl2/MeOH
Me2S, -78 °C+ H2N
OMe
O(1) NaCNBH4, MeOH NaOAc, 4 Å MS
(2) HOBt,Toluene, Reflux HN
N
MeO2C
Cbz
O
MeNH2, MeOH
(67%)
H2, Pd/C
DioxaneNH2
N
MeO2C
O(HCHO)n
20% TFA, CH2Cl2 NH
N
CO2MeO
N
NO
O
(95%) (48%)
Ac2O, Py
N
N
CO2MeO
(98%)
Ac
O
NH
Me
H
(90%)
Synthesis
δ (ppm)b Δδ/ΔT (ppb/K)c IR (cm-1)
NHMe 7.79 - 2.75 3351
•NMR e IR spectroscopical data. a
7,5
7,7
7,9
8,1
8,3
0 10 20 30
ppm
% DMSO-d6
Titration with DMSO-d6
a All analyses were performed on 3.0 mM CDCl3 solutions. b At 298 K. c Determined between 298 and 328 K.
X-Ray Structure (from isopropanol)
dα (Å) β (o) Φ2 (o) Ψ2 (o) Φ3 (o) Ψ3 (o)
Type II’ -turn 4.75 1.05 60 -120 -80 0
X-Ray 5.467 -11.98 48.86 -133.68 -89.44 10.79
MM 5.586 -19.54 51.69 -136.43 -103.77 41.15
HF (6-31G*) 5.942 -28.10 48.44 -136.52 -108.51 26.97
• Analysis of geometrical parameters of 3.
Application of the SIPP scaffold to mimic a bioactive peptide
N
NO
O
OBnBocHN
N
O CONHMe
H
HN N
NH2
NO2
1
2
3
1
2
1 2
3
3
4
4
1
2
1 2
1
G. Lesma, E. Meschini, T. Recca, A. Sacchetti, A. Silvani, Tetrahedron 2007, 63, 5567-5578;N. Landoni, G. Lesma, A. Sacchetti, A. Silvani, J. Org. Chem. 2007, 72, 9765-9768.