Hopanes

Yosioka etal. 342) have published a concluding statement concerning the stereostructure of the widely distributed lichen metabolite, zeorin (481). From X-ray analysis of 6-O-p-bromobenzoylzeorin the configuration of C-21 has been established as C-21 PH 246). This confirmed that zeorin, like leucotylin (482), was a hopane derivative with C-21 pH configuration. 

In addition to the previously described pyxinic acid (485) 339), Yosioka et al. 345) have isolated methyl pyxinate (486) and methyl 3-0-acetylpyxinate (487) from Pyxine endochrysina. The structure of these esters was verified by direct comparison with the synthetic derivatives obtained from pyxinic acid. 

A new hopane derivative, amphistictinic acid (488), has been isolated from Pseudocyphellaria amphisticta (273). The structural assignment followed principally from H-n.m.r. and mass spectral data and was confirmed by chemical conversion to hopane-15a,22-diol. 

16-0-Acetylleucotylin (489) and 20a-acetoxy-6a,22-dihydroxyhopane (490) were isolated from chemical strains of Physcia aipolia (134). The structures of these products were determined primarily from their C-n.m.r. spectra. The compound with the C-20 acetoxy group is of particular interest as it is the first example of a hopane triterpenoid with an oxygen substituent in this position. 

Corbett and Wilkins (59) have revised the structures of the triterpenoids obtained from Pseudocyphellaria mougeotiana (52). Following the discovery of the presence of the known triterpenoids, 7 3,22-di-hydroxyhopane (491) and 15a,22-dihydroxyhopane (492), the structures of the remaining triterpenoids present in this lichen were reinvestigated. It was 

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Comprehensive chemical analyses of samples of water, sediment, and biota were carried out both before and after the spill. This cannot of course be carried out in most cases, and illustrates a serious limitation in field studies, in which lack of background data or difficulty in finding an uncontaminated control locality is frequently encountered. Sum parameters were sparingly employed in Baffin Island Oil Spill (BIOS), and emphasis was placed on the analysis of specific compounds attention was directed not only to PAHs, but also to azaarenes, dibenzothiophenes, and hopanes. Thereby, a clear distinction could be made between the input from the oil deliberately discharged, and that arising from natural biological reactions or mediated by atmospheric transport. 

Dammar resin was introduced into Europe in the nineteenth century, mainly as a paint varnish It is still used today since it has good optical properties and low acidity. It is derived from various species (the genus Hopea and Shorea of the Dipterocarpaceae family). It is characterised by tetracyclic triterpenoids of the dammarane series and contains minor amounts of pentacyclic triterpenoids of the series of olanane, ursane and hopane. It also contains a polymeric fraction named polycadinene or [S-resene. Dammar resin triterpenoids undergo oxidation with ageing, as described for the components of mastic resin. 

Hook molecule, 16 264, 265 Hop a-acids, 3 570-571 Hopane, marker in bioremediation of oil spills, 3 788-789 Hop P-acids, 3 570-571 Hope diamond, 7 336 6 524 Hop essential oils, 3 572 Hopper dryers, 9 123-124 Hopper scales, 26 244, 246 design considerations for,... 

Figure 7.12 Potential biomarkers in bitumen the isoprenes (a) pristane (Ci9H40) and (b) phytane (C2oH42), and (c) the hopane 17o (H), 21/3(H)-pentakishomohopane (22R).

Fatty acids (methyl esters) FAMES TMS fragment Hopanes and hopenes Sterols (TMS)... 

Tetracyclic terpanes C24-Tetracyclic (17,21 -seco-hopane) C24H42 330... 

DDT converts in part to p,p -DDE over time in the environment, especially in sediments [151, 171]. An example of the total aliphatic extract of a sediment from the Los Angeles Bight contaminated with p,p -DDE is shown in Fig. 11. The TIC trace shows a major UCM and the minor resolved peaks are normal alkanes (primarily from higher plant wax), with mature 17a(H),21/ (H)-hopanes (from petroleum residues as is the UCM). The mass spectrum ofp,p -DDE is shown in Fig. 12a, registering the molecular ion cluster at m/z 316-320. DDE is detected in the m/z 246 fragmentogram (Fig. lid), appearing as a small peak in the TIC trace and DDT is not detectable in this sample. 

Luellen, D.A. and Shea, D. 2003, Semipermeable membrane devices accumulate conserved ratios of sterane and hopane petroleum biomarkers. Chemosphere S3 705-713. 

Saturated hydrocarbons n-Paraffins Isoparaffins and other branched paraffins Cycloparaffins (naphthenes) Condensed cycloparaffins (including steranes, hopanes) Alkyl side chains on ring systems... 

Of particnlar significance in the study of petroleum weathering are the biomarker molecules (e.g., pristane, phytane, the hopanes and steranes). Historically, the biomarkers have been employed as crude oil signatures in prospecting and characterization. More recently, such molecules have also been employed in the environmental field, both for the determination of pollutant source and estimation of the degree of weathering. 

Fig. 4. Scheme for the alteration of hopenoids to aromatic hopanoids and hopane (namtal product examples are boxed). 

The hopane series are the natural product biomarkers elucidated initially as attributable to bacteria.The 17a(H),2ip(H)-hopanes ranging from C27 to C35 (no C28) were encountered in numerous ancient sediments and petroleums, and diagenesis and maturation of the microbial precursors (e.g. bacteriohopanepolyol and diploptene, Fig. 4) were elucidated. The diagenesis of diploptene in contemporary sediments proceeds by double bond migration from via to... 

Fig. 12. Salient features of the GC-MS data for a hydrothermal petroleum (Guaymas Basin, Gulf of California, Mexico) (a) TIC trace of total oil, (b) mjz 191 key ion for hopanes, and ctmjz 217 key ion for steranes. Numbers refer to carbon chain (/ -alkanes) or skeleton, UCM = unresolved complex mixture, Pr = pristane, Ph = phytane, asterisks = other isoprenoids, ot, ot, R, S = configurations of biomarkers.

The characterization of a novel series of biomarkers is illustrated with the g 7 2-dialkylalkanes in bitumen from a hydrothermal system on the Mid-Atlantic Ridge. The total bitumen consists of hydrocarbons, a major UCM (unresolved complex mixture of branched and cyclic compounds) and mature biomarkers (e.g. hopanes) (Fig. 13a). The bitumen contains a series of cyclopentylalkanes Cfi 2n) that range from n = 14 to 34, with only even-chained pseudohomologs and a concentration maximum (Cmax) at n = 18. Their source is biogenic, based on the presence of only even-carbon number homologs, but the precursors are unknown. 

Ensminger A, van Dorsselaer A, Spyckerelle C, Albrecht P, Outisson G, Penta-cyclic tritetpenes of the hopane type as ubiquitous geochemical matkers Origin and significance, in Tissot B, Bienner F eds). Advances in Organic Geochemistry Editions Technip, Paris, pp. 245—260, 1974. 

Kajukova GI, Pustulnikova GD, AbruitinaNN, Golovkina LS, MeshtuevaVL, Petrov AA, Structural variations in hopane type hydrocarbons, Neftechimiya 21 803-811, 1981. 

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