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Pergamon 0146-6380 94)00110-3Org. Geochem,Vol. 23, No. 1, pp. 21-27, 1995Copyright 1995 ElsevierScienceLtdPrinted in Great Britain.All rights reserved0146-6380/95 $9.50 + 0.00

c c u r r e n c e o f 2 8 n o r 1 8 ~ o l e a n a n e i n t h e h y d r o u s p y r o l y s a t e o f al i gn i t e

CARIM ARMANIOS, l ROBERT ALEXANDE R, l ROBERT I. KAGI, IBRIAN W. SKELT ON 2 and ALL AN H. WHIT E 2~Australian Petroleum CRC/Centre for Petroleum Environmental Organic Geochemistry, CurtinUniversity of Technology, GPO Box U 1987, Perth, Western Australia 6001 and 2Department ofChemistry, University of Western Australia, Nedlands, Western Australia 6009

Received 23 May 1994; returned or revision 28 July 1994; accepted 20 September 1994)Abstraet--28-nor-18ct-Oleanane has been isolated from the hydrous pyrolysate of a Western Australianlignite and characterised by a single crystal X-ray structure determination.Key words--28-nor-18ct-oleanane, triterpane, lignite, X-ray crystallography, ~3C NMR spectroscopy,molecular sieves

INTRODUCTIONOleanane and 18ct-oleanane (I) occur in crude oilsand sediments (e.g. Ekweozor and Udo, 1988). Thesecompounds arise from either the defunctionalisationof higher plant derived natural product precursorssuch as the amyrins or from acid-induced conversionof other pentacyclic triterpenoids (Ames et al., 1954;Halsall et al., 1952; Coates, 1967; Rullk6 tter et aL,1994). In immature sediments oleanane is often themost abundant isomer (according to IUPAC rulesole anane has 18fl stereochemistry), but with in-creasing maturation the more thermodynamicallystable 18ct-oleanane assumes greater relative abun-dance (ten Haven and Rullk6tter, 1988; Ekweozorand Telnaes, 1990). In addition to these two isomers,24,28-bisnor-18a-oleanane has also been identified inpetroleum (Trendel et al., 1991). In this paper wereport the isolation and identification of 28-nor-18ct-oleanane from the hydrous pyrolysate of a lignite.

EXPERIMENTALSample

The Heartbreak lignite sample was obtained ascore material. The sample had been sealed in PVCtubes to prevent moisture loss and exposure to airduring storage. The lignite was from a deposit ofEocene age located in the Bremer Basin, southeasternWestern Australia.Isolation of a C29 triterpane

The coal was dried, crushed and extracted withdichloromethane for 48 h using a Soxhlet apparatus.The extracted coal (4 x 250 g) was pyrolysed in thepresence of water (150 ml) in a stainless steel vessel

(1L) at 330C for 72h. The aqueous phase wasextracted with dichloromethane and the insolublematerial air dried and extracted with dichloro-methane. The two extracts were combined and thesolvent removed by distillation. The bitumen extract(125 g) was subjected to a series of liquid chromatog-raphy procedures. First the extract was chromato-graphed on alumina to collect the less polarcomponents eluted with n-pentan e. This fraction waschromatographed on silica gel to obtain a totalalkane fraction which was then chromatographed onZSM-5 molecular sieve to give a branched and cyclicalkane fraction (4.5 g). A high molecular weightfraction (0.7 g) enriched in the 28-nor-18ct-oleananewas obtained by reduced pressure distillation of thebranched and cyclic alkane fraction. This was thenchromatographed on an ultrastable-Y modecularsieve colu mn 40 x 1 cm i.d. using n -pe nta ne andfractions were collected. The first eluted fraction,cont aini ng compound s which were too large to besorbed by the sieves, was comprised (75% by GC) oftwo pentacyclic hydrocarbons, namely a C29 (1) anda C30 (2) triterpane (Fig. la). The C29 triterpane(5.8 mg) was fractionally crystallised from the mix-ture using ethylmethylke tone (200 p l) as a solvent.Recrystal lisa tion from ethylacetate (150/~ 1) gave longneedle-like crystals suitable for a single crystal X-raystudy.X-ray crystallography

A unique room-temperature diffractometer dataset (T ~ 295 K; Enraf-Nonius machine, monochro-matic MoK~ radiation, 2 0.71073 ~; co scan mode,20m~~ 45 ) was measured for the un know n C29 triter -pane (Fig. l(a), peak 1), yielding 2693 independen treflections, 877 with I> 3 a ( I ) being considered

o~ 23,1~ 21

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22 Car im A r manios et al.

4 3I

Scheme 1.

~ C O O HNO 4 ~

4 3o b s e r v e d a n d u s e d i n t h e l ar g e b l o c k l e as t s q u a r e s

r e f i n e m e n t w i t h o u t a b s o r p t i o n c o r r e c t i o n .N M R s p e c tr o s co p y

A 13 C s p e c t r u m o f t h e u n k n o w n C 9 t r i t e r p a n e w a so b t a i n e d u s i n g a B r u k e r A R X - 5 0 0 n u c l e a r m a g n e t i cr e s o n a n c e s p e c t r o m e t e r o p e r a t i n g a t 1 27 .7 7 M H z .T h e ~3C c h e m i c a l s h i f t a s s i g n m e n t s w e r e r e c o r d e di n p p m r e l a ti v e t o T M S u s i n g C D C 1 3 a s i n t e rn a lr e f e r ence .G a s c h r o m a t o g r a p h y - m a s s s p e c t r o m e t r y

T h e a n a l y s i s o f b r a n c h e d a n d c y c li c a l k a n ef r a c t i o n s b y G C - M S w a s c a r r i e d o u t u s i n g aH e w l e t t - P a c k a r d 5 89 0 S e ri e s I I g a s c h r o m a t o g r a p hc o n n e c t e d t o a H P 5 9 7 1 m a s s s e l e c ti v e d e t e c t o ro p e r a t i n g a t 7 0 e V . T h e g a s c h r o m a t o g r a p h w a se q u i p p e d w i th a 4 0 m 0 . 1 8 m m i .d . f u se d s il ic ac a p i l l a r y c o l u m n c o a t e d w i t h a D B - 1 s t a t i o n a r y p h a s e( J & W ) . H e l i u m w a s u s e d a s t h e c a r r i e r g a s a t a l i n e a rf lo w v e l o c i t y o f 2 7 c m / s . T h e o v e n w a s p r o g r a m m e df r o m 7 0 t o 2 8 0 C a t 4 C / m i n .

RESULTS AND DISCUSSIONG C - M S a n a ly s is o f t ri te r p an e s

T h e h y d r o u s p y r o l y s a t e o f a li g n i te f r o m W e s t e r nA u s t r a l i a w a s s u b j e c te d t o s e q u e n t i a l t r e a t m e n t w i t ha l u m i n a , s i l ic a ge l , a n d m o l e c u l a r s i e v e s a n d f i n a l l y t or e d u c e d p r e s s u re d i s t i l la t i o n t o o b t a i n a h i g h m o l e c u -l a r w e i g h t b r a n c h e d a n d c y c li c a l k a n e f r a c t io n e n -r i c h e d i n t r i t e r p a n e s . F i g u r e l ( a ) s h o w s a p a r t i a lm / z 191 m a s s c h r o m a t o g r a m o f p e n t a c y c l i c t r i t e rp a n ec o m p o n e n t s i n t h e h y d r o u s p y r o l y s a t e . B e s i d e s t h eh o m o l o g o u s s e r ie s o f 1 7 g , 2 1 ~ ( H ) - h o p a n e s a n d m o r e -t a n e s , f o u r o t h e r t r i t e r p a n e s w e r e d e t e c t e d ( p e a k s1 4 ). A n u n k n o w n C 29 ( 1 ) t r i t e r p a n e , w h i c h h a s as l i g h t l y l o n g e r r e t e n t i o n t i m e t h a n 30- nor hopane ( 29) ,w a s t h e m o s t a b u n d a n t t r i t e r p a n e in t h is s a m p l e a n dis the subjec t o f th i s paper . A C30 t r i t e r pane ( 2) , a l soi s o l a t e d i n t h i s w o r k , w a s i d e n t i f i e d b y ~3C N M Rs p e c t r o s c o p y to b e l u p a n e . G C - M S a n a l y s i s o f th ec o m p o u n d r e p r e s e n t e d b y p e a k 2 u s i n g a p o l a r B P - 2 0c o l u m n , w h i c h e n a b l e d t h e c o m p l e t e r e s o l u t i o n o f

l u p a n e f r o m t h e o l e a n a n e s , c o n f i r m e d t h a t i t w a sa l m o s t e n t i r e ly c o m p r i s e d o f l u p a n e w i t h n o d e -t e c t a b l e c o n t r i b u t i o n f r o m e i t h e r o l e a n a n e o r 1 8 ~ -o l e a n a n e . A n o t h e r C 29 t r i t e r p a n e ( 3 ) , w h i c h e l u t e s j u s tb e f o r e h o p a n e ( 3 0 ) , w a s a l s o o b s e r v e d i n a T e r t i a r yc r u d e o i l fr o m I n d o n e s i a a n d w a s p r e v i o u s l y t e n t a -t ive ly iden t i f i ed as a 2 8 - n o r t a r a x a s t a n e ( A r m a n i o set al . 1994) . Las t ly , a C30 t r i t e r pa ne ( 4) w as ten ta -t i v e l y i d e n t i f i e d a s a t a r a x a s t a n e i s o m e r b a s e d o nm a s s s p e c t r a l f e a t u r e s a n d i t s r e p o r t e d G . C . r e t e n t i o nb e h a v i o u r ( e .g . R u l l k 6 t t e r et al . 1994).X- r ay s t ruc ture de term inat ion o f C29 t r i t e rpane

T h e m o l e c u l a r s t ru c t u r e a n d s t e r e o c h e m i s t ry o f t hei s o l a t e d C 2 9 t r i t e r p a n e ( m e l t i n g p o i n t o f 1 8 5 - 1 8 6 C )w a s e s t a b l i s h e d b y a s i n g l e c r y s t a l X - r a y s t u d y t o b e2 8 - n o r - 1 8 ~ - o l e a n a n e ( II ). T h e w e a k a n d l i m i te d d a t aa v a i l a b l e f r o m a m a r g i n a l l y s m a l l s p e c i m e n w o u l dn o t s u p p o r t m e a n i n g f u l a n i s o t r o p i c t h e r m a l p a r -a m e t e r r e f i n e m e n t a n d t h e i s o t r o p i c f o r m w a s r e f i n e dt h r o u g h o u t f o r C , O ; ( x , y , z , U i ,o )n w e r e i n c l u d e dc o n s t r a i n e d a t e s t i m a t e d v a l u e s . T h e a s s i g n m e n to f t h e m e t h y l s u b s t i t u e n t d i s p o s i t i o n t h r o u g h o u t ,n e v e r t h e l e s s , a p p e a r s u n a m b i g u o u s . C o n v e n t i o n a lr e s i d u a l s R , R w , o n I F [ a t c o n v e r g e n c e w e r e 0 . 0 7 4 ,0 .0 6 0 ( s t a t i s t ic a l w e i g h t s , d e r i v a t i v e o f a 2 ( i ) = a2I d i f f + 0 . 0 00 4 o 4 (l ai n- ). N e u t r a l a t o m c o m p l e x s c a t t e r -i n g f a c t o r s w e r e u s e d , c h i r a l i t y b e i n g a s s i g n e d f r o mt h e e x p e c t a t i o n s o f t h e a s s o c i a t e d ch e m i s t ry ; c o m p u -t a t i o n u s e d t h e X T A L 3 . 2 p r o g r a m s y s t e m ( H a l let al . 1992) . Pe r t inen t r e su l t s a r e g iven in F ig . 2 ( a )a n d T a b l e 1 ; f u ll m o l e c u l a r n o n - h y d r o g e n g e o m e t r ie sa n d t h e r m a l a n d h y d r o g e n p a r a m e t e r s h a v e b e e nd e p o s i t e d w i th t h e C a m b r i d g e C r y s t a l l o g r a p h i c D a t aC e n t r e .

Crys ta l da ta . C 2 9 H 5 0 , M 3 9 8.7 . O r t h o r h o m b i c ,space gr oup P212121 ( D ~ , N o. 19) , a 43 .27( 3) , b15.91(1), c 7.217(5) ~ . V 4970 ,~3 . D . ( Z = 8 )1 .0 7 g . c m - 3 ; F ( 0 0 0 ) 1 7 9 2 . ~M o 0 .6 c m - l ; s p e c i m e n :0 .04 0 .05 x 0 .62 mm.1~C N M R s p e c t r o sc o p yT h e ~3C N M R s p e c t r u m o f t h e 28- nor - 18~-o l e a n a n e s h o w e d 2 9 r e s o n a n c e s w h i c h w e r e r e s o l v e dw i t h t h e a i d o f D E P T e x p e r i m e n t s i n to s e v e n m e t h y l ,

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Occurrence of 28 nor 18ct oleanane in the hydrou s pyrolysate of a l ignite 23

m / z 1 9 1

2 9 2

17I x , 2 l l ~ ( H ) - hop ane sm o r e t a n e s

t r i te r p a n e s 1 - 4

a )

3 0

t 4 31R 31 32S S R

e~0

2929,

30

30

b )

t

31Rt s 3 2 R

5 0 5 5 6 0 6 5Retention time min)

Fig. 1. Partial m/z 191 mass chromatograms showing the presence of 28 nor 18~ oleanane in the hydrouspyrolysate branched and cycl ic a lkane f ract ion f rom two Aust ra l ian l ignites . (a) Hear tb reak l igni te f romthe Bremer Basin and (b) Loy Yang l igni te f rom the Gippsland Basin.

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2 4 C a r i m A r m a n i o s et at w e l v e m e t h y l e n e , f i v e m e t h i n e a n d f i v e q u a t e r n a r yc a r b o n s i g n a l s . T h e ~3C N M R c h e m i c a l s h i f t sT a b l e 2 ) w e r e a s s i g n e d b a s e d o n t h o s e r e p o r t e d f o r

24 28-d inor -18e t -o leanane T r e n d e l et al. 1991) andl u p a n e A m m a n n et al. 1982).

Mass spectrometryT h e m a s s s p e c t r u m o f 28-nor -18~-o leanane

F i g . 2 b ) s h o w s a s t r o n g C 29 m o l e c u l a r i o n a t m / z 3 9 8a n d a b a s e p e a k a t m / z 1 91 . F r a g m e n t i o n s a t m / z 260

~

a )C 9~

C2 A

C l A

C25A

CgA

C11AC 2A

C 6A

C 7A

C I lM

e 2 ~ f l ~ e4A

o

F i g . 2 a )

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O c c u r r e n c e o f 28-nor-18ct-oleanane i n t h e h y d r o u s p y r o l y s a t e o f a l i g n i te 2 5

1 0 0 %

8

. ~ 6 0~

4

2 0 5 5

51 9

L L t i 7 6 3L1 0 0

191

177

260

I I H q - - . _

2 4 5 2 6 0, I t 2 ~ 7 I I .2o0 300

- - m / z

b )

398383

I

4 0 0

F i g . 2 ( b )F i g . 2 . P r o j e c t i o n o f m o l e c u l e A n o r m a l t o a n d t h r o u g h t h e s k e le t al p l a n e s ( a ) a n d m a s s s p e c t r u m ( b )o f 28-nor-18t-oleanane i s o la t e d f r o m t h e h y d r o u s p y r o l y s a t e o f a l i g ni t e f r o m W e s t e r n A u s t r a l i a .

a n d m / z 2 4 5 a r e s u g g e s te d t o b e d u e t o A B C - r i n g a n dC D E - r i n g f r a g m e n t a t i o n , r e s p e c t i v e l y ,O r i g i n

2 8 - n o r - 1 8 c t - O l e a n a n e h a s a l ik e l y o r i g i n f r o m C - 2 8f u n c t i o n a l is e d n a t u r a l p r o d u c t s s u c h a s o l e a n - 1 2 - e n -3 f l -o l - 2 8 - o ic a c i d ( I l l ) w h i c h o c c u r w i d e ly i n e x t a n t

p l a n t s ( P a n t a n d R a s t o g i , 1 97 9 ; D a s a n d M a h a t o ,1 9 8 3 ) . D u r i n g d i a g e n e s i s , t h e s e n a t u r a l p r o d u c t p r e -c u r s o rs m a y u n d e r g o d e f u n c ti o n a li s a ti o n a n d h y d r o -g e n a t i o n t o g i v e 2 8 - n o r - t r i t e r p e n o i d s ( t e n H a v e ne t a l . 1 9 9 2 ) . B e c a u s e a c i d c a t a l y s e d i n t e r c o n v e r s i o no f t r it e r p a n e s o f d i ff e r e n t s k e le t a l t y p e s m a y o c c u r( e . g . A m e s e t a L 1954 ; H a l sa l l e t a l . 1 9 5 2 ; C o a t e s ,

T a ble 1 . Non-hydroge n pos i t iona l a nd i s o t rop ic d i s p la c e m e nt pa ra m e te r sAtom x y z U x y z U

Molecule A Molecule BC( I) 0.5890 (5) 0.538 (I) 0.793 (4) 0.047 (8) 0.6559 (5) 0.561 (1) 1.302 (4) 0.062 (9)C(2 ) 0.5916 (6) 0.638 (I) 0.819 (4) 0.060 (9) 0.6526 (5) 0.463 (1) 1,327 (4) 0.055 (8)C(3) 0.5907 (6) 0.679 (I) 0.632 (5) 0.065 (9) 0.6544 (5) 0.422 (1) 1.137 (4) 0.055 (9)C(4 ) 0.5627 (6) 0.659 (2) 0.511 (5) 0.053 (9) 0.6836 (6) 0.438 (2) 1.014 (4) 0.050 (9)C(5) 0.5594 (6) 0,560 (2) 0.499 (4) 0.05 (I) 0.6872 (5) 0.539 (l ) 1.023 (4) 0.031 (8)C(6 ) 0.5317 (5) 0.528 (I) 0.378 (4) 0.037 (8) 0.7119 (6) 0.563 (2) 0.896 (4) 0.051 (9)C(7 ) 0.5387 (5) 0.434 (2) 0.330 (5) 0.062 (9) 0.7101 (5) 0.658 (l ) 0.834 (4) 0.044 (8)C(8) 0.5424 (6) 0.376 (2) 0.487 (4) 0.039 (8) 0.7061 (6) 0.717 (2) 0.996 (4) 0.043 (9)C(9 ) 0.5657 (5) 0.414 (1) 0.637 (4) 0.039 (8) 0.6818 (5) 0.683 (l) 1.132 (4) 0.039 (8)COO ) 0.5608 (6) 0.513 (2) 0.676 (5) 0.054 (9) 0.6860 (5) 0.585 (I ) 1.199 (4) 0.041 (8)C 0 1) 0.5690 (6) 0.358 (2) 0.813 (5) 0.08 (1) 0.6779 (6) 0.742 (2) 1.304 (4) 0.054 (8)C(12) 0.5789 (5) 0.269 (I) 0.744 (4) 0.054 (9) 0.6692 (5) 0,832 (1) 1.235 (4) 0.048 (9)C(13) 0.5590 (5) 0.230 (2) 0.606 (4) 0.032 (8) 0.6925 (6) 0.869 (2) 1.102 (4) 0.045 (9)C(14) 0.5564 (5) 0.284 (2) 0.428 (4) 0.031 (9) 0.6944 (6) 0.809 (2) 0.935 (4) 0.046 (9)C(15) 0.5356 (6) 0,245 (2) 0.287 (5) 0.07 (l) 0.7185 (5) 0.845 (1) 0.786 (4) 0.048 (8)C(16) 0.5428 (6) 0.153 (2) 0.236 (5) 0.061 (9) 0.7096 (5) 0.936 (2) 0.739 (4) 0.057 (9)C(17) 0.5457 (5) 0.099 (2) 0.413 (4) 0.047 (9) 0.7086 (5) 0.989 (2) 0.903 (5) 0.048 (9)C(18) 0.5690 (6) 0.137 (l ) 0.548 (4) 0.035 (8) 0.6850 (5) 0.958 ( I) 1,042 (4) 0.033 (9)C(19) 0.5711 (5) 0.083 (2) 0.719 (4) 0.050 (9) 0.6835 (5) 1.017 (1) 1.218 (4) 0.052 (8)C(20) 0.5798 (6 ) -0 .0 12 (2) 0.667 (4) 0.051 (9) 0.6776 (7) 1.114 (2) 1.161 (5) 0.09 (1)C(21) 0.5576 (6) -0 ,0 46 (2) 0.535 (5) 0.07 (1) 0.6988 (7) 1.138 (2) 1.013 (5) 0.08 (1)C 22) 0.5542 (5) 0,009 (2) 0.367 (5) 0.06 (I) 0.7014 (5) 1.085 (2) 0.852 (4) 0.055 (9)C(23) 0.5324 (6) 0.701 (2) 0.589 (5) 0.08 (l) 0.7103 (5) 0.394 (1) 1.106 (4) 0.048 (8)C(24) 0.5648 (6) 0.693 (2) 0.321 (5) 0.08 (I) 0.6779 (6) 0.404 (2) 0.846 (5) 0.08 (1)C(25) 0.5328 (5) 0.523 (2) 0.817 (4) 0.059 (8) 0.7123 (5) 0.571 (2) 1.322 (4) 0.057 (8)C(26) 0.5106 (5) 0.364 (I ) 0.571 (4) 0.051 (8) 0.7381 (5) 0.724 (1) 1.088 (4) 0.059 (9)C(27) 0.5875 (5) 0.298 (1) 0.338 (4) 0.048 (8) 0.6639 (5) 0.802 (1) 0.837 (4) 0.048 (8)C(29) 0.6126 (6) -0 .01 8 (2) 0.592 (5) 0.08 (I) 0 .6446 (6) 1.120 (I) 1 .089 (5) 0.065 (9)C(30) 0.5789 (5) -0 .0 62 (1) 0.858 (4) 0.059 (9) 0.6784 (6) 1.163 (2) 1.340 (5) 0.08 (1)

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26 Carim Armanios et al.Table 2. ~3C Chemical shift assignments (ppm relative toTMS) for lupane (Ammannet al., 1982), 24,28-bisnor-18~-oleanane (Trendel et a l . , 1991) and 28-nor-18~-oleanane

24,28-bisnor- 28-nor-Carbon Lu pa ne 18~-Oleanane 18~-Oleanane1 40.36 39.81 40.372 18.69 21.51 18.69~3 42.16 36.63 42.114 33.20 30.58 33.265 56.36 54.42 56.466 18.72 20.97 18.60~7 34.42 33.06 33.888 41.12 40.49t 40.779 50.25 48.55 50.5810 37.47 37.07 37.4411 21.88 21.21 20.8912 26.94 25.03 24.9013 37.88 43.04 42.9814 43.08 41.61t 41.5015 27.36 31.06 31.1116 35.61 29.66 29.5717 43.12 43.75 43.6918 47.69 37.88 37.8219 44.75 43.94 43.8620 29.36 31.09 31.0521 21.93 39.19 39.1122 40.43 30.41 30.3323 33.34 20.54 33.3524 21.57 -- 21.5425 16.00 14.13 16.2526 16.08 15.78 15.7027 14.49 14.91 15.0228 18.08 -- - -29 15.13 25.39 25.3530 22.93 33.74 33.69

*t:~ ~3C resonance assignments are interchangeable.

1967) and such processes have been repor ted to occurin sediments (e.g. ten Haven and Rullk6tter, 1988;Ekweozor and Telnaes, 1990), it can be inferred that,provided the absence of a substituent at C-28 doesnot inhibit the rearrangement processes, 2 8 - n o r - 1 8 0 t -oleanane may be derived from a range of other2 8 - n o r - t r i t e r p e n o i d s .

The presence of 2 8 - n o r - 1 8 ~ - o l e a n a n e in thehydrous pyrolysate but not in the soluble organicmatter indicates that it is intimately associated withthe kerogen. This association may be due to thetriterpane being physically entrapped or alternativelybeing chemically bound to the kerogen.

This occurrence of 2 8 - n o r - 1 8 c t - o l e a n a n e in a ligniteformed in a temperate climate and the reportedoccurrence of 2 8 - n o r olean- 12-ene-3-one in sedimentsfrom the Mahakam Delta (Corbet e t a l . , 1980) de-posited in very different climatic conditio ns suggeststhat 2 8 - n o r - o l e a n a n e s might be more widespread insedimentary organic matter of Tertiary age than haspreviously been recognised. A comprehensive studyof the occurrence of 2 8 - n o r - 1 8 ~ - o l e a n a n e in sedimen-tary organic mat ter is beyo nd the scope of this paper,however its presence in the pyrolysate of anotherlignite from a different basin (Fig. lb) suggests to usthat it may be common to Tertiary lignites. Datapresented here confirms doubts expressed by tenHaven e t a l . (1992) regarding the authenticity of aprevious assignment of 2 8 - n o r - o l e a n a n e in a Jurassiccoal by Wang e t a l . (1990). Their compound had asignificantly lower GC retention time (relative to

3 0 - n o r h o p a n e compared with that for our authenticstandard. One explanation for the apparent absenceof 2 8 - n o r - 1 8 ~ - o l e a n a n e in sediments and crude oils isthat it is poorly resolved from C29Ts (Mol dow ane t a l . , 1991) and the spirotriterpane (Hills e t a l . , 1968)in gas chromatograms obtained using commonstationary phases an d may have gone un detected (e.g.Ekweozor and Udo, 1988).A s s o c i a t e E d i t o r A . G . RequejoA c k n o w l e d g e m e n t s - - W e thank CRA exploration Pty Lim-ited for providing the lignite sample and Dr Lindsay Byrnefor carrying out the ~3C NM R analysis. C.A. acknowledgesfinancial support in the form of an Australian PostgraduateResearch Award (APRA).

REFERENCESAmes T. R., Beton J. L., Bowers A., Halsall T. G. and JonesE. R. H. (t954) The chemistry of the triterpenes andrelated compounds. Part XXIII. The structure of taraxas-terol, tp-taraxasterol (heterolupeol), and lupenol-I.J . Chem. Soc . 1905 1919.Ammann W., Richarz R., Wirthlin T. and Wendisch D.(1982) I H and t3C chemical shifts and coupling constantsof lupane. Application of two-dimensional NMR tech-niques. O r g . M a g n . R e s . 20, 260 265.Armanios C., Alexander R., Kagi R. I. and SosrowidjojoI. B. (1994) Fractionation of sedimentary higher-plantderived pentacyclic triterpanes using molecular sieves.Org . Geochem. 21, 531-543.Coates R. M. (1967) On the friedelene-oleanene rearrange-ment. Te trahedron Le t t . 13, 4143 4146.Corbet B., Albrecht P. and Ourisson G. (1980) Photochem-ical or photomimetric fossil triterpenoids in sedimentsand petroleum. J . A m e r . C h e m . S o e . 102, 1171-1173.Das M. C. and Mahato S. B. (1983) Triterpenoids. P h y t o -c h e m i s t r y 22, 1071 1095.Ekweozor C. M. and Telnaes N. (1990) Oleanane par-ameter: Verification by quanti tative study of the bio-marker occurrence in sediments of the Niger delta. InAdvances in Organ ic Geochemis t ry 1989 (Edited byDurand B. and Behar F.), pp. 401 413 . Pergamon Press,Oxford.Ekweozor C. M. and Udo O. T. (1988) The oleananes:Origin, maturation and limits of occurrence in SouthernNigeria sedimentary basins. In Advances in Organ ic Geo -

c h e m i s t r y 1987 (Edited by Mattavelli L. and Novelli L.),pp. 131-140. Pergamon Press, Oxford.Hall S. R., Flack H. D. and Stewart J. M. (Eds) (1992) TheXTAL 3.2 reference manual. Universities of WesternAustralia, Geneva and Maryland, 1992.Halsall T. G., Jones E. R. H. and Meakins G. D. (1952) Thechemistry of triterpenes and related compounds. Part XI.The conversion of lupeol into germanicol (isolupeol).The structure of lupeol hydrochloride. J . Chem. Soc .2862-2867.ten Haven H. L., Peakman T. M. and Rullk6tter J. (1992)Early diagenetic transformation of higher-plant triter-penoids in deep-sea sediments from Baffin Bay. Geoch im.C o s m o c h i m . A c t a 56, 200l 2024.ten Haven H. L. and Rullk6tter J. (1988) The diageneticfate of taraxer-14-ene and oleanene isomers. Geoch im.C o s m o c h i m . A c t a 52 2543 2548.Hills I. R., Smith G, W. and Whitehead E. V. (1968)Optically active spi rotr iterpane in petroleum distillates.N a t u r e 219, 243 246.

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O c c u r r e n c e o f 28-nor-18ct-oleanane i n t h e h y d r o u s p y r o l y s a t e o f a l i g n i t e 27M o l d o w a n J . M . , F a g o F . J . , C a r l s o n R . M . K . , Y o u n gD . C . , V a n D u y n e G . , C l a r d y J . , S c h o e l l M . , P i l l i n g e rC . T . a n d W a t t D . S . 1 9 91 ) R e a r r a n g e d h o p a n e s i ns e d i m e n t s a n d p e t r o l e u m . Geochim. Cosmochim. Acta 55 ,3333-3353 .P a n t P. a n d R a s t o g i R . P. 1 9 79 ) T h e t r it e r p e n o i d s . Phyto-chemistry 18 , 1095-1108 .R u l l k 6 t t e r J . , P e a k m a n T . M . a n d t e n H a v e n H . L . 1 9 94 )E a r l y d i a g e n e s i s o f t e r r i g e n o u s t r i t e r p e n o i d s a n d i t s i m p l i-

c a t i o n s f o r p e t r o l e u m g e o c h e m i s t r y . Org. Geochem. 21 ,2 1 5 - 2 3 3 .T r e n d e l J . - M . , G r a f t R . , A l b r e c h t P. a n d R i v a A . 1 9 91 )24 28-Dinor-18~t-oleanane a n o v e l d e m e t h y l a t e d h i g h e rp l a n t d e r i v e d t r it e r p e n e h y d r o c a r b o n i n p e t r o l e u m . Tetra-hedron Left. 32 , 2959-2962 .W a n g T . - G . , S i m o n e i t B . R . T . , P h i l p R . P . a n d Y u C . - P .1 9 90 ) E x t e n d e d 8 f l H ) - d r i m a n e a n d 8 14-seco-hopanes e ri e s i n a C h i n e s e b o g h e a d c o a l . Ener. Fuels 4, 177 183.