Aliphatic and aromatic triterpenoid hydrocarbons in a Tertiary angiospermous lignite

Org. Geochem.Vol. 18, No. 1, pp. 51-66, 1992 Printed in Great Britain. All rights reserved

0146-6380192$5.00+ 0.00 Copyright© 1992PergamonPress plc

Aliphatic and aromatic triterpenoid hydrocarbons in a Tertiary angiospermous lignite SCOTT A. STOUT Unocal Science and Technology Division, P.O. Box 76, Brea, CA, 92621, U.S.A. (Received 14 November 1990;returnedfor revision 12 January 1991;accepted in revisedform 23 April 1991) Abstract--The hydrocarbon biomarker assemblage of a liptinite-rich, early Tertiary angiospermous lignite has been characterized. The biomarker distribution for the lignite confirms the low maturity and previous paleobotanic interpretations. The aliphatic hydrocarbon fraction consists predominantly of n-alkanes showing a strong odd-carbon predominance, and numerous de-A-triterpenoids and triterpenoids derived from higher plants. Bacterially-derived triterpenoids were represented primarily by homohopanes and hopenes. The aromatic hydrocarbon fraction contains a series of mono-, di-, and triaromatic de-A-triterpenoids and mono-, tri-, and tetraaromatic triterpenoids derived from higher plants. The concentration and abundance of monoaromatic triterpenoids containing one to three additional degrees of unsaturation have not been previously observed in a single deposit. As such, a diagenetic scheme for angiosperm-derived triterpenoids is presented which confirms and extends previous hypotheses. Key words--biomarker, brown coal, triterpenoids, oleanoids, ursanoids, angiosperm, de-A-triterpenoids

INTRODUCTION

riverine body of water surrounded by densely vegetated banks. The Brandon peat formed in a subtropical climate and supported an exclusively angiosperm flora such as is currently found in many of the swamps bounding small rivers in the southeastern U.S. (e.g. Ogeechee River, Georgia or Suwanee River, Fla). In addition to the paleobotanic studies, the Brandon lignite has been the focus of several organic petrographic and geochemical studies (Stout et aL, 1988; Boon et aL, 1989; Stout and Boon, in preparation; Stout, 1988; Hohn and Meinschein, 1977). However, these investigations have neglected the extractable hydrocarbons and concentrated on geopolymers and fatty acids present in fossilized tissues. The excellent preservation of lignins and carbohydrates in selected fossils testifies to the high degree of preservation (Stout et al., 1988; Boon et al., 1989; Stout and Boon, in preparation). Rarely has the paleobotany, petrography, depositional setting, and relative rank of an organic deposit been more extensively characterized. As such, the Brandon lignite offers an excellent opportunity to study the hydrocarbons found in an immature, wellpreserved, early Tertiary organic sediment formed exclusively from dicotyledonous angiosperm trees and shrubs (of known taxa) in a freshwater fluvial environment.

The distribution of biomarkers in brown coals has received considerable attention in the past two decades. Brown coal and lignite extracts from around the world have been investigated (reviewed by WoUrab and Streibl, 1969; Chaffee et al., 1986; Wang and Simoneit, 1990; Chaffee, 1990). These studies have documented extensive diagenetic changes which occur on the molecular level during the transformation of plant materials into coal. In addition, the contributions of microorganisms (as determined by hopanoid moieties) and certain plant taxa (as determined by gymnosperm resin-derived diterpenoids and specific angiosperm-derived triterpenoids) have been shown. This study is intended to increase our understanding of terrestrial biomarker distributions and their diagenesis by examining a lignite deposit found on the eroded uplands of New England, U.S.A. The Oligocene Brandon lignite, Vermont, has received considerable paleobotanic study due to the excellent preservation of fossil fruit endocarps and woods contained in the deposit (Lesquereux, 1861; Knowlton, 1902; Perkins, 1904; Barghoorn and Spackman, 1950; Tiffney and Barghoorn, 1976; Traverse, 1955). The Brandon flora overwhelmingly consisted of dicotyledonous angiosperm trees and shrubs; very few herbaceous plants are represented probably due to the early Tertiary age of the deposit (Traverse, 1955). Common taxa represented by megafossils included swamp-margin genera such as Carya, Cyrilla, Gordonia, Magnolia, Nyssa, Quercus, and Persea. Collectively, the paleobotanic investigations have shown that the Brandon lignite formed in a small

EXPERIMENTAL

A homogenized channel sample through the entire deposit was used to characterize the lignite. A 25 g sample was extracted by stirring in a tolueneacetone-methanol mixture (70:15:15) at room 51

52

SCOTTA. STOUT Table 1. Results of the combined maceral analysis of the Brandon lignite % Huminitic macerals Textinite Ulminite Attrinite Densinite Gelinite Corpohuminite Total Liptinitic macerals Liptodetrinite Sporinite Cutinite Resinite Suberinite Fluorinite

Total

Inertinite macerals Sclerotinite

literature or tentatively assigned according to spectral interpretation.

1 10 45 I ] 8 66

RESULTS AND DISCUSSION

Table 1 shows the maceral composition of the sample studied. Other relevant information on the sample can be found elsewhere (Stout and Boon, in preparation). 66% of the organic matter is huminitic, mostly derived from degraded cell wall material. This fact emphasizes the terrestrial origin of the organic matter present. However, the lignite contains little inertinite (2%) and a relatively large percentage of liptinitic macerals (32%) consisting predominantly of finely dispersed liptodetrinite 06%). This is especially interesting since coals high in liptinite macerals (e.g. cutinite, resinite, sporinite, suberinite, liptodetrinite) have been regarded as sources of liquid hydrocarbons (Murchison, 1987; Khorasani, 1987; Saxby and Shibaoka, 1986). The whole coal yielded 19,711 ppm extract (1.97% by wt), of which 5.6% were aliphatic hydrocarbons, 5.3% were aromatic hydrocarbons, and 89.1% contained heteroatomic compounds. The aliphatic and aromatic hydrocarbon fractions will be discussed separately. Commonly referenced structures are enumerated with roman numerals and shown at the end of the paper. Spectral characteristics of referenced peaks are given in the Appendix.

16 4 6 2 3 1 32 2

temperature. The aliphatic hydrocarbon, aromatic hydrocarbon, and heteroatomic compound fractions of the extract were obtained using silica-gel chromatography eluting with n-hexane, dichloromethane, and methanol, respectively. Biomarker analyses of the aliphatic and aromatic hydrocarbon fractions were obtained by full scan GC-MS using a Hewlett-Packard 5890 gas chromatograph coupled to a VG 70-250SE high resolution mass spectrometer set at (approximately) 1000 resolving power (R.P.). Scans were made over a mass range of 60-600 amu. Mass spectra are shown following background subtraction. A 30 m fused silica capillary column coated with DB-5 (0.25/~m) was used. Chromatographic conditions were: injector temperature 290°C, flow rate 1 ml min ~, splitless for first 80s, oven program 40°C(2)/20°C min-l/150°C/3°C min-]/310°C(13). Identifications of compounds were made via comparison with reference mass spectra from the

Aliphatic hydrocarbons The reconstructed ion current (RIC) for the aliphatic hydrocarbon component of the extract is shown in Fig. 1. It can be seen that it is dominated by a series ofn-alkanes ranging from C23 to C35 which reach a maximum at hentriacontane (C3)H64). These n-alkanes are thought to derive from epicuticular

Triterpenoids

r

100

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80-90'

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De-A-Triterpenoids

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O. SCAN 500 TIME (rain) 15:02

1000 26:04

1500 37:05

2000 48:07

2500 59:08

3000 1:10:10

Fig. I. RIC of aliphatic hydrocarbon fraction of the Brandon lignite extract.

Aliphatic and aromatic triterpenoid hydrocarbons waxes of higher plants (Tissot and Welte, 1984), an interpretation that is supported by the relative abundance of cutinite in this coal (Table 1). There is a strong odd dominance, yielding a CPI (as calculated from the m / z 253 mass chromatogram, not shown, using the equation of Allan and Douglas, 1977) of 6.8 which is typical of brown coals and lignites. This high value is consistent with the low rank and higher plant origin of the Brandon lignite organic matter (Chaffee et al., 1986). The odd predominance is probably due to the early diagenetic defunctionalization of even-numbered alcohols, acids, and esters (Tissot and Welte, 1984). Twelve compounds eluting between n-C23 and nC26 (Fig. 2) comprise of a series of de-A-triterpenoid hydrocarbons (e.g. structure I). Similar compounds have been observed in petroleum and various sediments (including lignites) and are thought to arise from photochemically and/or, more likely, microbially-mediated oxidative loss of the A-ring from 3-oxygenated pentacyclic triterpenes (e.g. ~t- and flamyrin; structures II-III; Corbet et al., 1980; Trendel et al., 1989). The presence of these compounds not only testifies to the input of angiospermous organic matter but also tends to confirm the loss of ring A as a common transformation pathway of higher plant triterpenoids (Corbct et al., 1980; Trendel et al., 1989). The series of de-A-triterpenoids are characterized by M + 324 (C24H36), 326 (C24H3s), 328 (C24H40),and 330 (C24H4:; Fig. 2). Only peak H has been confidently identified as de-A-lupane (structure I) by comparison to published spectra (Philp, 1985). The remaining peaks represent similar compounds, most probably with a six-member E-ring (as indicated by the lack of significant M+-43, characteristic of isopropyl loss from five-member E-ring lupenoid structures), i.e. derived from ~- and fl-amyrin skeletons (structures II or III) with one to three degrees of unsaturation. None of the unknown compound's spectra matched those recently published for synthetic de-A-lupenes or de-A-oleanadienes (Trendel et al., 1989) or for speculated de-Afernenes (Loureiro and Cardoso, 1990). Thus, the

A

53

position(s) of the double bonds are not known but one possibility is the A12(as in the ~ - and fl-amyrin skeleton; structures H and HI). Other possibilities include Ais or A13(is) [e.g. de-A-olean-13(18)-ene, compound B?]. Additional double bonds probably occur in the B-ring which is thought to be the first to aromatize (Spyckerelle et al., 1977a). Spectral characteristics of some of the remaining de-A compounds appear in the Appendix. The diagenetic importance of these compounds will be discussed later in the paper. Figure 3 shows the expanded triterpenoid region of the aliphatic hydrocarbon fraction shown in Fig. 1. Two groups of triterpenoid-type hydrocarbons are present in the extract; (1) bacterially-derived hopanoids and (2) unsaturated angiosperm-derived triterpenes. Each of these is discussed briefly below. Bacteria typically synthesize 17fl(H),21fl(H)hopanes which convert to 17~(H),21fl(H)-hopanes and 17fl(H),21~(H)-moretanes during diagenesis (Ries-Kautt and Albrecht, 1989) and with maturation (Ensminger et al., 1974; Tissot and WeRe, 1984). Among the bacterially-derived hopanes in this lignite, 22R-17a(H),21fl(H)-homohopane (peak B') is the most prominent. This C3~-hopane is also relatively abundant in other low rank coals (Ensminger et al., 1974; Hazai et al., 1988). Its 22S-isomer is present in much lower concentration (peak A'), suggesting a low rank. Other hopanes present are all of the 17fl(H)type further suggesting immaturity. These include 17fl(H)-22,29,30-trisnorhopane (peak M), 17fl(H), 21fl(H)-30-norhopane (peak Z), 17fl(H),21fl(H)-hopane (peak C'), and 17~(H),21/~(H)-homohopane (peak D'). Two unsaturated hopanoids, hop-17(21)erie (peak U) and neohop-13(18)-ene (peak Y), were also detected further indicating immaturity. No C~sor C3~_33-hopaneswere detected. The second group of compounds also indicates immaturity. Numerous olefinic C30 compounds with one (M ÷ 410; peaks Q, R, T, V, W, and X) or two degrees of unsaturation (M + 408; peaks N, O, P, and S) occur. Among these, oleana-9(1 l),12-diene (peak O; structure V), oleana-2,12-diene (peak P; structure IV), olean-13(18)-ene (peak Q), olean-12-ene (peak

BI De-A-triterpanes

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Fig. 2, RIC of de-A-triterpenoid region of aliphatic hydrocarbon fraction of Brandon lignite extract.

54

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Angiosperm-derived triterpenoids

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Fig. 3. RIC of triterpenoid region of aliphatic hydrocarbon fraction of Brandon lignite extract. R), two fernenes (peaks T and X), and urs-12-ene (peak V) were assigned after comparison with published spectra (Philp, 1985) and the recent authentic standard results of ten Haven et al. (1991, 1992). The unidentified monounsaturated compound (M ÷ 410; peak W) is likely to be an isomer of the angiosperm-derived triterpenoids described above. Similarly, those unidentified compounds with M ÷ 408 (peaks N and S) may represent doubly unsaturated equivalents of these triterpenoids, based on the similar fragment ions observed for the M ÷ 410 and M ÷ 408 compounds (i.e. m / z 257, 255, 231,218, 205, 203, 191, 189 and/or 187 are observed among both the known and unknown compounds). Compound S has a base peak of m / z 187 suggesting that two double bonds exist on the A- or B-ring. The presence of unsaturated angiosperm-derived triterpenoids in this immature coal is consistent with the proposed diagenesis of such angiosperm-derived triterpenoids (see below). The absence of the saturated angiosperm-derived triterpenoids (e.g. oleanane or ursane) further suggests the immature nature of the deposit. The oleanane family of compounds, along with the ursane, fernane, lupane, and friedelane families typify dicotyledonous angiosperm-derived organic matter (Hills et al., 1970). The presence of oleanadienes (compounds O and P), oleanenes (compounds Q and R), fernenes (compounds T and X) and ursene (compound V) testify to the significant input of angiospermous organic matter to the Brandon lignite. Ferneries, however, have also been reported to occur in bacterially-derived immature sediments (Brassell et al., 1983). The apparent absence of lupenes or friedelenes suggests that the plants in which these compounds occur may not have been among the

Brandon flora (as described above). Alternatively, these compounds have not yet been identified among the unknowns. Though steroids are typically absent from low rank coals, the occurrence of diasterenes in brown coals was recently reported (Winkler, 1986; Hazai et al., 1989; Wang and Simoneit, 1990). However, no steroids were observed in the Brandon lignite aliphatic fraction in spite of the known occurrence of freshwater dinoflageltates in the overlying silt (Traverse, 1955). Aromatic hydrocarbons

The RIC of the aromatic hydrocarbons extracted from the Brandon lignite is shown in Fig. 4. Once again, few low molecular weight compounds are present with the exception of the sesquiterpenoids, calamenene and cadalene. Figure 5 shows an expanded area of Fig. 4 (scans 1350-2000) which contains four groups of aromatic hydrocarbons. These groups are: (1) monoaromatic (B-ring) de-A-C:3 triterpenoids (pentamethyldodecahydrochrysenes; structure VI), (2) diaromatic (B,C-rings) de-A-C22 triterpenoids (tetramethyloctahydro-chrysenes; structure VII), (3) triaromatic (B,C,D-rings), de-A-C2] triterpenoids (trimethyltetrahydro-chrysenes; structure VIII), and (4) several unknown compounds. Characteristic spectra and tentative structures of several unknown monoaromatic (B-ring) de-A-triterpoids are shown in Fig. 6. C23 compounds with structure Vl were present with zero to two additional degrees of unsaturation [M ÷ 310, 308, 306; Fig. 6(A-C)]. These compounds probably represent degraded and aromatized angiosperm-derived triterpenoids with ~t- and ~-amyrin (structures II and III)

Aliphatic and aromatic triterpenoid hydrocarbons

55

Triterpenoids !

100-

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908070(fJ Z tu I-

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De-A-triterpenoids ! i

30-

1000 26:04

SCAN 500 TIME (mln) 15:03

1500 37:06

2000 48:07

2500 59:09

3000 1:10:10

Fig. 4. RIC of aromatic hydrocarbon fraction of Brandon lignite extract• skeletons. The location of the double bond(s) (when present) are not known but are presumed to occur in the 12, 18, and/or 13(18) positions as they occur in the oleanenes and ursenes found in the aliphatic fraction. Similarly, the positions of the methyl groups are implied based on the oleanane- and ursane-type structures• These compounds produce characteristic fragment ions at m / z 187, 172, and 159 [Fig. 6(A42)]. A similar compound (M ÷ 310) was found in the Messel shale and an oleanoid structure was proposed (Spyckerelle et al., 1977a). Figure 6(D) shows the spectra of a compound thought to be a C24 aromatized (B-ring) 100 -

de-A-triterpenoid. The large number of C23 and Cu compounds observed (peaks 1-5, 9, 11-14, 16; Fig. 5) with similar spectra suggests that a large number of isomers are present• Mass spectral characteristics of these unknown or tentatively identified compounds are given in the Appendix• Compound 6 (Fig. 5) is one of four (peaks 6-8 and 10) diaromatic (B,C) de-A-triterpenoids (structure VII; M ÷ 292). This particular oleanoid-derived compound (and the ursanoid-derived compound, peak 8; Fig. 5) was identified by comparison to published spectra (Spyckerelle et al., 1977a; Laflamme and Hites, 1979; Wakeham et al., 1980) •

12

Monoaromatic De-A-triterpenoids

m Diaromatic De-A-triterpenolds

90-

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Triaromatic Oe-A-triterpenoids

00-

A 70_-2

16

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SCAN 1,'o0 TIME (mln) 34:54

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1600 ' 39:18

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Fig. 5. RIC of aromatic de-A-triterpenoid region of aromaic hydrocarbon fraction of Brandon lignite extract•

56

SCOTT A. STOUT

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Aliphatic and aromatic triterpenoid hydrocarbons

cation of peaks 23 and 24 as A, B, D-ring triaromatic, C-ring cleaved (8,14-seco) olcanoid- (structure IX) and ursanoid-derived (structure X) compounds respectively. These identifications are based on comparison to published mass spectra (compounds D and E from Chaffee et aL, 1984) and recent 1H-NMR results on extracts from Australian brown coals (Chaffee and Fookes, 1988). Such compounds are thought to form by photochemical and/or acid catalyzed cleavage of C-ring dienes (Chaffee et al., 1984). The aromatic hydrocarbons are dominated by a series of compounds which, based on their mass spectra, are considered monoaromatic (A-ring) triterpenoids (peaks 25-36, 38, and 41). Angiospermderived 3-oxy-triterpenoids are thought to progressively aromatize, via microbial action, from the A-ring to the D-ring (Streibl and Herout, 1969). Although a few monoaromatic triterpenoid compounds have been observed in some (East) German brown coals (Hazai et al., 1989), such an extensive distribution of monoaromatic pentacyclic compounds from a single deposit have not previously been reported. Thus their prominence in the Brandon lignite extract is unusual and may testify to relatively low microbial activity in the Brandon swamp, as also indicated by the excellent plant tissue preservation in the deposit. The series of monoaromatic triterpenoids have molecular ions of M + 362 (peak 30), 372 (peaks 34, 36), 374 (peaks 25, 26, 33, 41), 376 (peaks 27-29, 31, 35, 38), and 378 (peak 32), which suggests them to be C:7 (with one additional degree of unsaturation) and C2s (with zero to three additional degrees of unsaturation) compounds. Some characteristic spectra and structures are shown in Fig. 8. Identifications could be made for only three of these compounds based on spectral comparison with published synthetic standards (Wolff et al., 1989). Structures XI, XII, and XIII represent peaks 28, 31, 32 respectively. The

and has recently been assigned a C-18 cis configuration based on NMR (Chaffee and Fookes, 1988). This type of compound has been isolated from recent lake sediments (Laflamme and Hites, 1979; Wakeham et al., 1980) although its occurrence has been reported also in the Eocene Messel shale (Spyckerelle et al., 1977a). Peaks 7 and 10 are considered previously unreported isomers of these B,C-ring diaromatic compounds. A pair of compounds with the B, C, and D-rings aromatized (structure VIII) are present (peaks 15, 17). The oleanoid (peak 17) and the ursanoid analog (peak 15) were identified by their spectra and relative retention times, and have been found in recent river and lake sediments and the Tertiary deposit mentioned above (Spyckerelle et al., 1977a; Laflamme and Hites, 1979; Wakeham et aL, 1980). Two unknown compounds with molecular weights o f m / z 320 (peaks 18 and 19) elute around scan 1875. These C24H32 compounds may represent the further unsaturated equivalents of compound 4 [M ÷ 322; Fig. 6(d)]. Likewise compounds 20 (M ÷ 346, base m/z 159), 21 (M ÷ 354, base m/z 354), and 22 (M ÷ 360, base m/z 345) have not been identified. Characteristics of their mass spectra are found in the Appendix. Figure 7 shows an expanded portion of the RIC of the aromatic hydrocarbon fraction (scans 2000-2600; Fig. 4). Apparent overloading of the GC column did not seem to influence spectral quality. Again four groups of compounds were identified as: (1) triaromatic (A, B, and D-rings) C-ring cleaved (8,14-seco) tetracyclic triterpenoid-derived compounds, (2) monoaromatic (A-ring) triterpenoids, (3) triaromatic (A, B, and C-ring) triterpenoids, and (4) tetraaromatic (A, B, C and D-ring) triterpenoids. The first group of compounds have molecular ions at M ÷ 356 and base peaks of m/z 169 (i.e. trimethylnaphthalene fragments) which supports the identifi100 9080-

57

•

TrlaromaUc Seco-Trlterpenolds

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Monoaromatic Tflterpenoids

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Fig. 7. RIC of aromatic triterpenoid region of aromatic hydrocarbon fraction of Brandon lignite extract.

58

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Aliphatic and aromatic tdterpenoid hydrocarbons oleanoid [Fig. 8(D)], ursanoid, and lupanoid skeletons are all represented as might be expected from their presence in the aliphatic hydrocarbon fraction described above. Unfortunately, all of the other monoaromatics are still unidentified, but are thought to be isomers and unsaturated equivalents of the three known compounds (XI, XII, and XIII). Some tentative structures appear in Fig. 8(A-C) and spectral information on the remaining compounds appears in the Appendix. These monoaromatics produce a series of characteristic fragment ions such as m / z 145, 158, 170, and 219 depending on the degree of unsaturation in the B and C-rings. This is demonstrated in the mass chromatograms and proposed fragmentation schemes shown in Fig. 8. The m / z 145 and 158 fragments most likely originate from the A and B ring mono- and dimethyl-tetrahydronaphthalene fragments. The positions of the various double bonds are not known although they probably occur in various positions in the B, C, D and perhaps even E rings. Beyond signaling angiosperm triterpenoid contribution to the Brandon lignite, the diagenetic significance of the presence of such a large suite of these compounds will be discussed below. Also represented in Fig. 7 are five compounds identified as A, B, C-ring triaromatic triterpenoids, all with molecular weights of 342 amus (peaks 37, 39, 40, 42, 43). It is worthwhile to note that there were no A and B-ring diaromatic triterpenoids (M ÷ 360) observed in the extract. (The mass spectra of compound 22 does not indicate a diaromatic structure.) Comparison to published spectra indicates that peaks 39 and 42 are A, B, C-ring triaromatic triterpenoids (structures XIV and XV) which have been shown to occur in the extracts of brown coals and recent sediments (Wakeham et al., 1980; Chaffee and Johns, 1983; Chaffee and Fookes, 1988). The other peaks (37, 40, 43) are thought to represent previously unknown isomers of these structures. The spectral characteristics of these compounds are given in the Appendix and their importance in the diagenesis of higher plant triterpenoids will be discussed below. The last group of four compounds in Fig. 7 are A-D-ring tetraaromatic triterpenoid-derivatives with molecular weights of 310, 324, and 340 amus. Compounds 45 and 47 occur in other sediment and lignite extracts and have ursanoid and oleanoid structures XVI and XVII respectively (Wakeham et al., 1980; Chaffee and Johns, 1983; Chaffee and Fookes, 1988). A mass spectral search suggests that compound 44 may have a hopanoid-like structure (XVIII; Spyckerelle et al., 1977b; Greiner et al., 1977; Laflamme and Hites, 1979; Wakeham et al., 1980). However, considering the relative low abundance of hopanoids compared to higher plant triterpenoids encountered in the extract, it is more likely that compound 44 has a 24,30-bisnorlupanoid structure (XVIII'). This compound has also been found in recent sediments and the Messel shale (Spyckerelle et

59

al., 1977b; Greiner et al., 1977; Laflamme and Hites, 1979; Wakeham et al., 1980). Compound 46 (M + 340) is unidentified but probably represents a C26H28 tetraaromatic triterpenoid. Characteristics of the mass spectra of these compounds appear in the Appendix. Implications for the diagenetic angiosperm-derived triterpenoids

transformation

of

The wide array of aliphatic and aromatic angiosperm-derived triterpenoids in the Brandon lignite allows for certain conclusions concerning diagenetic pathways to be drawn. The presence of aromatized triterpenoids in recent and immature sediments (Streibl and Herout, 1969; Laflamme and Hites, 1979; Wakeham et al., 1980; Chaffee et al., 1984; Chaffee and Fookes, 1988; Hazai et al., 1989; Wolff et al., 1989) suggests that the dehydrogenation of triterpenoids does not require long periods of time nor increased temperature. In addition, the presence of both aliphatic and aromatic higher plant-derived triterpenoids with various degrees of unsaturation within the same deposit suggests that the process(es) which govern dehydration do not ubiquitously affect all triterpenoids present at the same rate. As such the diagenesis of angiosperm-derived triterpenoids is thought to be controlled predominantly by photolytic and microbial processes rather than by thermal stress. Numerous studies of aromatic hydrocarbons extracted from recent and immature sediments have presented diagenetic schemes for higher plant triterpenoids. Collectively it has been reported that their diagenesis proceeds via one of several pathways, i.e. (l) cleavage of the A-ring followed by progressive aromatization from the B to E rings ultimately resulting in chrysene-like compounds, (2) aromatization of the A-ring followed by progressive aromatization of the B-D rings ultimately resulting in picene-like compounds, or (3) cleavage of the C-ring resulting in aromatized seco-triterpanes (Streibl and Herout, 1969; Spyckerelle et al., 1977a, b; Laflamme and Hites, 1979; Chaffee et al., 1984; Hazai et al., 1989). Pathways 1 and 2 are initiated due to the oxygen functionality in the 3-position (e.g. structures II and IIl) which is deemed necessary for either A-ring cleavage or aromatization (Streibl and Herout, 1969; Wolff et al., 1989). The Brandon lignite aliphatic and aromatic hydrocarbons contain nearly every "intermediate" for the first two of these diagenetic pathways and thus serve to support them further. This is illustrated in the hypothetical pathways for the diagenesis of the ~tand/or fl-amyrin skeletons (structures II and III) shown in Fig. 9. Only the compounds identified or tentatively identified in the Brandon lignite extract are shown on the figure and corresponding peak assignments are indicated. Exact positioning of double bonds on individual compounds is not critical to the scheme but the most likely positions, based on mass spectral interpretation, are shown as solid lines

60

SCOTTA. STOUT

R3

R=OorOH

RS ~- amyrin skeleton

o.-amyrin skeleton

I l:",rog;':ssivo [ Aromatization]

...........

I

f 2",
] I

]

Aroma:ization I

hv[

With Aromat,za,ion !

t (N O P S)

~

I

' M+ 362 (?) ~

[~I~'~ r -

M+ 376 ~

~

~

(27-29,31,35,38)

c;2

~.~C

z 2

(25,~,33,4~1

|

M+360 (?) (22)--"

I

| •

~ C

<23,24)

(D,G)

C2"t~ ~ I M+320'322'324(?) I (4,13,18,19)\ ]

2

~

/

/

2

<39,4-~',42,43,

M+ 310 (5,11~,16)

~

(.~c2

t/

<1,9,14~

/" ~,N~C

~

NN, ~ C 2

M*372 ~ (34,36)

C

:

v ~ C 2

<6-8,10) ~

M+ 27._44 (15,17)

(45,47)

Fig.9. Diageneticpathwaysfor higherplanttriterl~noidsas representedfromBrandonligniteextractable hydrocarbons,

Aliphatic and aromatic triterpenoid hydrocarbons while alternative positions are dotted. Of course, a similar diagenetic scheme could be proposed for skeletons with a five-member E-ring (e.g. lupeol). Progressive aromatization of the land plant triterpenoids does seem to proceed from the A-ring to the E-ring. Of course, no absolute proof exists for this " A - E " scheme of progressive aromatization. However, the presence of the extensive array of rnonoaromatic "intermediates" (with zero, one, two, or three additional degrees of unsaturation) and triaromatic "intermediates" (with zero or one additional degrees of unsaturation) in the Brandon extract tend to support the progressive aromatization scheme in Fig. 9. Some intermediates in progressive aromatization (pathway 1) are more abundant than others while some are absent. For example, the relative abundance of M + 410 and M + 376 over M + 408 compounds suggest that aromatization of the A-ring proceeds rather rapidly once it is initiated. Similarly, A-ring monoaromatic triterpenoids with one (M ÷ 376) and two (M + 374) additional degrees of unsaturation are abundant, indicating that they are relatively longlived intermediates which are not readily converted into further aromatized species. On the other hand, those monoaromatic triterpenoids with three additional degrees of unsaturation (M ÷ 372) are minor suggesting that they are short-lived intermediates which are readily further aromatized. No diaromatic intermediate species (M + 360) were observed suggesting these compounds are also shortlived intermediates. (Compound 22 has an M + 360 but the prominent fragment ion, m / z 145, suggests it to be monoaromatic.) Diaromatic triterpenoids have not been observed in other brown coals containing aromatized triterpenoids (Chaffee and Johns, 1983; Hazai et aL, 1986; Chaffee and Fookes, 1988) which supports this conclusion. Although the presumed endproducts of the progressive aromatization of triterpanes, i.e. methylated picenes and chrysenes, have been observed in less mature sediments (Wakeham et al., 1980), their absence from the Brandon extract suggests that the aromatization of the triterpenoids is not complete. Since microbial activity, in part, controls the dehydrogenation reactions (Streibl and Herout, 1969; Spyckerelle et al., 1977a, b; Laflamme and Hites, 1979; Hazai et al., 1989), the absence may be due to reduced microbial activity in the Brandon swamp (recall the excellent degree of tissue preservation in the peat led to many preserved megafossils). Fission of the A-ring (pathway 2) is thought to be relatively quick, as no intermediates were observed. It has even been suggested that A-ring fission may occur photolytically in the plant prior to sedimentation (Corbet et al., 1980; Baas, 1985) which could explain the lack of seco-A-triterpenoids in the Brandon lignite and other immature sediments. The subsequent aromatization process of the de-Atriterpanes also appears to proceed in a rather systmatic manner. Monoene (M + 328), diene (M +

61

326), and triene (M + 324) de-A-triterpenoids are present in similar proportions suggesting that all are equally stable. Similarly, mono-aromatic de-A-triterpanes (M + 310, 308, 306) are present in similar proportions suggesting that gradual dehydrogenation has occurred. However, the di- and triaromatic de-Atriterpanes (M + 292 and 274) are less abundant than their monoaromatic precursors, possibly reflecting the instability of the latter compounds, or suggesting again that the aromatization process was incomplete. The absence of intermediates along pathway 3 [e.g. aliphatic seco-(8,14)-triterpenoids or monoaromatic seco-(8,14)-triterpenoids] suggests that (1) the aromatization and cleavage reactions are very rapid, or (2) the triaromatic seco-(8,14)-triterpenoids (M + 356) are a side-product of pathway 1, perhaps from the C-ring cleavage of the fragile 8(14) bond and rearrangement of monoaromatic dienes such as 25, 26, 33, 41 (M + 374) and/or trienes such as 34 or 36 (M + 372). This alternative pathway is shown as a dashed line connecting pathways 1 and 3 in Fig. 9. Such a reaction would indicate that photochemicallymediated or acid catalyzed C-ring cleavage would follow microbially-mediated aromatization as suggested by Chaffee et al. (1984). A photochemically-mediated reaction would clearly need to take place, either prior to sedimentation (e.g. in the senescent or dead plant) or in the surface litter stage of peatification, when sunlight is available. With increasing maturity the ultimate end products of pathway three should be methylated tetralins or naphthalins [following cleavage of the 9(11), 11(12), or 12(13) bonds; Villar et al., 1988]. However, calamenene and cadalene (Fig. 4), the only tetralins and naphthalins detected in the Brandon lignite extract, were derived from sesquiterpenoid rather than triterpenoid precursors. Thus, cleavage of the 9(11), 11(12), or 12(13) bonds presumably occurs at a higher level of coalification than is represented by the Brandon lignite. By comparing the relative abundance of triterpenoid compounds with the A-ring intact to those with a degraded A-ring, it is clear that the former compounds are more abundant (Figs 1 and 4). Thus for the pentacyclic triterpenoids in the lignite, it is apparent that pathway 1 (progressive aromatization) is preferred to pathway 2 (A-ring degradation followed by progressive aromatization). Similarly, the low concentration of seco-(8,14)-triterpenoids (peaks 23, 24; Fig. 4) relative to other triterpenoids suggest that pathway 3 (C-ring cleavage with aromatization) is incidental and uncertain. However, as stated above, pathway 3 may simply be an extension of pathway 1. Alternatively, pathway 3 may become favored at higher levels of maturation. CONCLUSIONS (1) The biomarker assemblage of the aliphatic and aromatic fractions from late-Oligocene Brandon

62

SCOTTA. STOUT

lignite, Vermont contain an overwhelming adundance of angiosperm-derived triterpenoids (oleanoids, ursanoids, lupanoids, and fernoids) and de-A-triterpenoids in various states of unsaturation and aromatization. Also present are leaf wax-derived n-alkanes with a strong odd-carbon predominance and bacterially-derived homohopane (prominent), hopane isomers, and hopenes. (2) The biomarker assemblage supports the paleobotanic and petrographic characterization of the lignite as being; (1) derived nearly exclusively from freshwater angiosperm taxa, (2) liptinite-rich, and (3) immature~ (3) The wide array of terrigenous triterpenoids present in the lignite extract permits the proposal of a diagenetic scheme for angiosperm-derived triterpenoids which supports and supplements previously proposed schemes. The three pathways recognized are (1) progressive aromatization from ring A to E (predominant), (2) cleavage of ring A followed by progressive aromatization from ring B to E (secondary), and (3) cleavage of ring C accompanied by aromatization of tings A, B, and D (incidental). (4) Many tentatively-identified aliphatic, monoaromatic, triaromatic, and tetraaromatic higher plantderived triterpenoid "intermediates" with various degrees of unsaturation are newly reported from this one deposit. Acknowledgements--The author wishes to thank Drs J. Curiale, L. ten Haven, T. M. Peakman, W. Pfittmann, and Cs. Sajg6 for their critical and constructive reviews and UNOCAL management for permission to publish this work.

REFERENCES

Allan J. and Douglas A. G. (1977) Variations in the content and distribution of n-alkanes in a series of Carboniferous vitrinites and sporinites of bituminous rank. Geochim. Cosmochim. Acta 41, 1223-1230. Baas W. J. (1985) Naturally-occurring seco-ring-A-triterpenoids and their possible biological significance. Phytochemistry 24, 1875-1889. Barghoorn E. S. and Spackman W. (1950) Geological and botanical study of the Brandon lignite and its significance in coal petrology. Econ. Geol. 45, 344--357. Boon J. J., Stout S. A., Genuit W. and Spackman W. (1989) Molecular paleobotany of Nyssa endocarps. Acta Bot. Need. 38, 391-404. Brassell S. C., Eglinton G. and Maxwell J. R. (1983) The geochemistry of terpenoids and steroids. Biochem. Soc. Trans. 11, 575 586. Chaffee A. L. (1990) Molecular indicators of diagenesis in lignite diastereomeric configuration of triterpenoid derived aromatic hydrocarbons. Org. Geochem. 15, 485-488. Chaffee A. L. and Fookes C. J. R. (1988) Polycyclic aromatic hydrocarbons in Australian coals--III. Structural elucidation by proton nuclear magnetic resonance spectroscopy. Org. Geochem. 12, 261-271. Chaffee A. L. and Johns R. B. (1983) Polycyclic aromatic hydrocarbons in Australian coals--L Angularly fused pentacyclic tri- and tetraaromatic components of Victorian brown coals. Geochim. Cosmochim, Acta 47, 41-2155. Chaffee A. L., Hoover D. S., Johns R. B. and Schweighardt F. K. (1986) Biological markers extractable from coal. In

Biological Markers in the Sedimentary Record (Edited by

Johns R. B.), pp. 311-345. Elsevier, Amsterdam. Chaffee A. L., Strachan M. G. and Johns R. B. (1984) Polycyclic aromatic hydrocarbons in Australian coals-II. Novel tetracyctic components from Victorian brown coal. Geochim. Cosmochim. Acta 48, 2037-2043. Corbet B., Albrecht P. and Ourisson G. J. (1980) Photochemical or photomimetric fossil terpenoids in sediments and petroleum. J. Am. Chem. Soc. 102, 1171-1173. Ensminger A., van Dorsselaer A., Spyckerelle C., Albrecht P. and Ourisson G, (1974) Pentacyclic triterpanes of the hopane type as ubiquitous geochemical markers: origin and significance. In Advances in Organic Geochemistry 1973 (Edited by Tissot B. and Bienner F.), pp. 245-260. Editions Technip, Paris. Greiner A. Ch., Spyckerelle C., Albrecht P. and Ourisson G. (1977) Aromatic hydrocarbons from geological sources. Part V. Mono-aromatic and di-aromatic hopane derivatives. J. Chem. Res. (M) 3829-3871. ten Haven H. L., Peakman T. M. and Rullkotter J. (1992) Early diagenetic transformation of higher plant triterpenoids into desmethyl derivatives and other oxidative degradation products. Submitted to Geochim. Cosmochim. Acta.

ten Haven H. L., Peakman T. M. and Aubry C., Stout S. A. and Rullkotter J. (1991)AZ-Triterpenes: early intermediates in the diagenesis of terrigenous triterpenoids. Abst. Org. Geochem. Conf., Manchester, England. Hazai I., Alexander G., and Szekely T. (1989) Study of aromatic biomarkers in brown coal extracts. Fuel 68, 49-54. Hazai I, Alexander G., Essinger B. and Szekely T. (1988) Identification of aliphatic biological markers in brown coals. Fuel 67, 973-982. Hazai I., Alexander G., Szekely T., Essinger B. and Radek D. (1986) Investigations of hydrocarbon constituents of a yGung subbituminous coal by gas chromatography-mass spectrometry. J. Chromatogr. 367, 117--133. Hills 1. R., Smith G. W. and Whitehead E. V. (1970) Hydrocarbons from fossil fuels and their relationships to living organisms. J. Inst. Pet. London 56, 1-137, 27--137. Hohn M. E. and Meinschein W. G. (1977) Fatty acids in fossil fruits. Geochim. Cosmochim. Acta 41, 189-193. Khorasani G. K. (1987) Oil-prone coals in the Walloon Coal Measures, Surat Basin, Australia. In Coal and CoalBearing Strata (Edited by Scott A. C.), pp. 303-310. Blackwell, Boston. Knowlton F. H. (1902) Notes on the fossil fruits and lignites of Brandon, Vermont. Bull. Torrey Bot. Club 29, 635~o41. Laflamme R. E. and Hites R. A. (1979) Tetra- and pentacyclic, naturally-occurring, aromatic hydrocarbons in recent sediments. Geochim. Cosmochim. Acta 43, 1687-- 1691. Lesquereux L. (1861) On the fossil fruits an lignite of Brandon, Vermont. Am. J. Sci. 32, 355-363. Loureiro M. R. B. and Cardoso J. N. (1990) Aromatic hydrocarbons in the Paraibab Valley oil shale. Org. Geochem. 15, 351 359. Murchison D. G. (1987) Recent advances in organic petrology and organic geochemistry: an overview with some reference to 'oil from coal'. In Coal and Coal-Bearing Strata (Edited by Scott A. C.), pp. 257-302. Blackwell, Boston. Perkins G. H. (1904) On the lignite or brown coal of Brandon and its fossils. Vt State Geol. 4, 153-162, 174-212. Philp R. P. (1985) Fossil Fuel Biomarkers--Applications and Spectra. Elsevier, Amsterdam. Ries-Kautt M. and Albrecht P. (1989) Hopane-derived triterpenoids in soils. Chem. Geol. 76, 143-151. Saxby J. D. and Shibaoka M. (1986) Coal and coal macerals as source for oil and gas. Appl. Geochem. 1, 25-36.

Aliphatic and aromatic triterpenoid hydrocarbons Spyckerelle C., Greiner A. Ch., Albrecht P. and Ourisson G. (1977a) Aromatic hydrocarbons from geological sources, Part IV: An octahydrochrysene derived from triterpenes, in oil shale: 3,3,7,12a-tetramethyl- 1,2,3,4,4a, I 1,12,12a-octahydrochrysene. J. Chem. Res. (M) 3801-3828. Spyckerelle C., Greiner A.Ch., Albrecht P. and Ourisson G. (1977b) Aromatic hydrocarbons from geological sources. Part III. A tetrahydrochrysene derived from triterpenes, in recent and old sediments: 3,3,7-trimethyl-l,2,3,4tetrahydrochrysene. J. Chem. Res. (M) 3746-3777. Stout S. A. (1988) Tracing the microscopical and chemical origin of huminite macerals in coal. Unpublished Ph.D. thesis. Penn State Univ. Stout S. A., Boon J. J. and Spackman W. (1988) Molecular aspects of the peatification and early coalification of angiosperm and gymnosperm woods. Geochim. Cosmochim. Acta 52, 405--414. Streibl M. and Herout V. (1969) Terpenoids---cspecially mono-, sesqui-, di- and triterpanes. In Organic Geochemistry--Methods and Results (Edited by Eglinton G. and Murphy M. T. J.), pp. 401-424. Springer, Berlin. Tiffney B. H. and Barghoorn E. S. (1976) Fruits and seeds of the Brandon lignite, I. Vitaceae. Rev. Palaeobot. Palynol. 22, 169-191. Tissot B. P. and Welte D. H. (1984) Geochemical fossils and their significance in petroleum formation. In Petroleum Formation and Occurrence, 2nd edn, pp. 93-130. Springer, Berlin. Traverse A. (1955) Pollen analysis of the Brandon lignite, Vermont. U.S. Bur. Mines, Rep. Invest. 5151.

63

Trendel J. M., Lohmann F., Kintzinger J. P. and Albrecht, P. (1989) Identification of des-A-triterpenoid hydrocarbons occurring in surface sediments. Tetrahedron 45, 4457--4470. Villar H. J., Piittman W. and Wolf M. (1988) Organic geochemistry and petrography of Tertiary coals and carbonaceous shales from Argentina. In Advances in Organic Geochemistry 1987(F_xlited by Mattavelli L. and Novelli, L.). Org. Geochem. 13, 1011-1021. Pergamon Press, Oxford. Wakeham S. G., Sehaffner C. and Giger W. (1980) Polycyclic aromatic hydrocarbons in Recent lake sediments--II. Compounds derived from biogenic precursors during early diagenesis. Geochim. Cosmochim. Acta 44, 415-429. Wang T. G. and Simoneit B. R. T. (1990) Organic geochemistry and coal petrology of Tertiary brown coal in the Zhoujing mine, Baise Basin, South China. Fuel 69, 12-20. Winkler E. (1986) Organic geochemical investigations of brown coal lithotypes. A contribution to facies analysis of seam banding in the Helmstedt depost. In Advances in Organic Geochemistry 1985(Edited by the Leythaeuser D. and Rullk6tter J.). Org. Geochem. I0, 617-624. Pergamon Press, Oxford. Wolff G. A., Trendel J. M. and Albrecht P. (1989) Novel monoaromatic triterpenoid hydrocarbons occurring in sediments. Tetrahedron 45, 6721-6728. Wollrab V. and Streibl M. (1969) Earth waxes, peat, montan wax and other organic brown coal constituents. In Organic Geochemistry--Methods and Results (Edited by Eglinton G. and Murphy M. T. J.), pp. 576-598. Springer, Berlin.

APPENDIX Mass Spectral Characteristics Peak I.D.

MW

Aliphatics A 326 B 328 C D E F G H

326 324 326 328 324 330

I

328

J

328

K

326

L

328

M N

370 408

O P

408 408

Q

41o

R S T

410 408 410

U

410

Most significant ions and abundance* 326(100), 311(50), 173(50), 229(25) 313(100), 328(80), 109(70), 205(65), 189(55), 95(45), 203(35), 123(30), 81(30), 69(30) 326(I00), 311(90), 229(45), 215(30) 324(100), 309(85) 326(100), 311(45), 229(30), 173(30) 313(100), 218(45), 328(35), 203(30), 95(25) 309(100), 324(90), 95(30) 123(100), 136(85), 109(80), 149(80), 163(70), 81(70), 69(45), 191(45), 192(40), 330(40) 123(100), 95(95), 109(95), 121(90), 328(75), 81(70), 122(70), 136(60), 217(55), 189(55) 136(100), 109(85), 95(70), 123(65), 189(60), 81(60), 121(60), 328(55), 107(55), 175(50) 136(100), 121(85), 326(85), 109(80), 326(80), 107(75), 189(70), 203(65), 95(60), 81(55) 123(100), 109(95), 95(90), 121(75), 189(70), 328(65), 136(65), 81(60), 122(50), 191(45) 149(100), 191(70), 95(35), 81(30), 69(25), 109(25) 191(100), 95(75), 177(75), 69(70), 109(65), 81(55), 190(55), 205(55), 149(50), 123(45) 408(100), 255(55), 218(35), 69(30), 95(25) 218(100), 95(85), 109(85), 69(70), 70(65), 203(60), 81(50), 123(50), 189(50), 121(45) 205(100), 218(95), 109(90), 191(85), 95(70), 69(65), 206(55), 204(50), 81(50), 410(45) 218(100), 203(30) 187(100), 393(90), 218(40), 394(30) 71(100), 85(80), 243(75), 231(60), 69(50), 205(40), 109(30), 95(30), 395(30), 218(25) 71(I00), 85(75), 410(55), 205(50), 69(50), 95(45), 189(40), 367(40), 135(30), 395(30)

Compound name

Refit

de-A-olean-13(18)-eneff)

de-A-lupane

A

1711(H)-22,29,30-trismorhopane

A

oleana-9(11), 12-diene oleana-2,12-diene

B C

olean- 13(I 8)-ene

A

olean-12-ene

A

ferene

A

hop- 17(21)-ene

A Continued overleaf

64

SCOTT A. STOUT Mass Spectral Characteristics (cont.)

Peak I.D.

MW

V W

410 410

X

410

Y

410

Z A'

398 426

a' C' D'

426 412 426

Most significant ions and abundance* 69(100), 85(70), 218(30), 99(25) 190(100),95(75), 69(70), 205(65), 109(60), 81(55), 175(50), 123(45), 121(45), 274(35) 243(100), 395(80), 95(35), 69(30), 396(25), 257(25), 410(25) 191(100),205(70), 69(55), 218(50), 95(50), 149(45), 109(40), 81(40), 410(40), 204(35) 177(100),191(60), 95(30), 81(25), 69(25) 191(100),95(50), 205(45), 81(35), 69(30), 426(30), 411(24) 191000), 95(35), 205(30), 81(25) 191(100),97(25) 205(100), 191(45), 95(30)

Compound name urs-12-ene

Ref.t A

~rnene neohop-13(18)-ene 17fl(H),21fl(H)-30-norhopane 17~(H),21fl(H)-homohopane(22S) 17~(H), 21fl(H)-homohopane (22R) 17fl(H), 21#(H)-hopane 17fl(H),21#(H)-homohopane

Aromatics

1

308

2 3 4 5 6

306 306 322 310 292

293(100), 145(65), 308(40), 157(40), 95(35), 171(25), 294(25) See Fig. 6(A) 187(100),145(35), 306(25), 119(25) See Fig. 6(D) 295(100), 157(55), 213(45), 131(35), 310(25) 292(100), 168(25), 155(25)

7 8

292 292

292(100), 207(95), 209(50), 208(45), 193(25) 292(100), 207(50), 209(30), 249(30), 193(25)

9

308

10 11 12 13

292 310 310 324

14 15 16 17 18

308 274 310 274 320

19

320

20 21 22 23 24 25

346 354 360 356 356 374

26

374

27 28 29 30 31 32 33 34 35 36 37 38 39

376 376 376 362 376 378 374 372 376 372 342 376+ 374 342

308(100), 293(50), 198(45), 145(40), 183(40), 71(35), 85(25), 169(25) 277(100), 292(75), 207(50), 193(30) 145(100),171(45), 146(35), 172(30), 159(25) 171(I00), 173(85), 174(45), 159(35), 310(30) 324(100), 134(70), 119(50), 202(50), 145(45), 91(25), 187(25) See Fig. 6(B) 259(100), 274(85) See Fig. 6(C) 274(100), 218(95), 219(25), 202(25) 305(100), 320(90), 195(55), 207(50), 221(35), 69(30), 181(25), 306(25) 305(100), 320(80), 195(55), 207(50), 221(35), 69(30), 193(25), 181(25), 306(25) 159(100),346(25) 354(100), 339(45), 201(30), 159(25), 283(25) 345(100), 360(45), 145(35), 171(25) 169(100),187(25), 356(25) 169(100),187(25), 356(25) 169(100),170(95), 203(55), 155(55), 374(50), 156(45), 205(35), 319(35), 95(25), 145(25) 156(100),171(70), 374(60), 155(50), 170(50), 221(30), 259(25), 145(25), 203(25), 252(25) 145(I00), 158(60), 170(35), 376(25) See Fig. 9(D) 170(100),155(65), 156(40), 376(35), 221(25) See Fig. 9(A) 145(I00), 158(70), 376(25), 361(25) 145(100),144(30), 146(25), 378(25) See Fig. 9(C) See Fig. 9(B) 145(100),376(25) 372(100), 219(95), 221(75), 220(65), 233(35), 222(25) 342(100) 145(100),207(45), 195(40)

40 41

342 374

342(100), 257(95), 259(35), 258(30)

3,3,7,12a-tetramethyl- 1,2,3,4a, 11,12,12a-octahydro chrysene

D

3,4,7,12a-tetramethyl- 1,2,3,4a, 11,12,12a-octahydro chrysene

3,4,7-trimethyl- 1,2,3,4-tetrahydro chrysene

E

3,4,7-trimethyl- 1,2,3,4-tetrahydro chrysene

E

Compound XVII in Compound E in

F G

24,25-dinoroleana- 1,3,5(10), 12-tetraene

H

24,25-dinorursa- 1,3,5(10), 12-tetraene 24,25-dinorlupa- 1,3,5( 10)-triene

H H

2,2,4a,9-tetramethyl- 1,2,3,4,4a, 5,6,14b-octahydro picene

E

342(100), 145(35), 257(30) 195(100),374(65), 221(25) Continued on facing page

Aliphatic and aromatic triterpenoid hydrocarbons

65

Mass Spectral Characteristics (cont.)

Peak I.D.

MW

42

342

342(I00), 327(35), 257(35)

43 44

342 310

342(100), 327(80) 281(100), 310(55), 265(30), 266(25), 282(25)

45 46 47

324 340 324

324(100), 309(60) 340(100), 324(60), 325(35), 309(35), 258(30), 285(30) 324(I00), 268(55) 2,2,9-trimethyl-l,2,3,4-tetrahydro picene

Most significant ions and abundance*

Compound name

Ref.t

1,2,4a,9-tetramethyl-l,2,3,4,4a, 5,6,14b-octahydro picene

E

7-methyl-1'-ethyl-1,2-cyclopenteno chrysene 1,2,9-trimethyl-l,2,3,4-tetrahydro picene

F F

*Ten most intense ions at least 25% of base peak (excluding M + isotopes). tA, Philp (1985); B, ten Haven et al. (1992); C, ten Haven et al. (1991); D, Spyckerelle et al. (1977a); E, Wakeham et al. (1980); F, Chaffee and Fookes (1988); G, Chaffee et al. (1984); H, Wolff et al. (1989); I, Laflamme and Hites (1979).

24 23

I. de-A-lupane

H.a-amyrin

~ ~ ~ C2

M

I

~

C2

~r.

J

C2

C2

~-. 9(11),12-amyrin

2

viii.

Tit

HI. ~-amyrin

24,25-dinoursa1,3,5(10),12tetraene

24,25-dinoroleana1,3,5(10),12-tetraene

Ix-

Xl[T[.24,25-dlnolupa1,3,5(10)tetraene

]~r. 2,2,4a~,9-tetramethyl1,2,3,4,4a,5,6,14b~octahydropicene

~DZ'.1,2,4a,9-tetramethyl 1,2,3,4,4a,S,6,14b~octahydroplcene

continued overleaf

0(3 IS/I--E

66

SCOTT A. STOUT

Referenced Structures (cont.)

~[.

1,2,9-trimethyl1,2,3,4tetrahydropicene

xvll.

2,2,9-trimethyl1,2,3,4tetrahydropicene

XVlll. 7-methyl-3'-ethyl1,2cyclopentenochrysene

~Z]]]" 7-methyl-l'-ethyl1,2cyclopentenochrysene