Hopane triterpene

Rohmer M., Anding C., Ourisson G. (1980) Nonspecific biosynthesis of hopane triterpenes by a cell-free system from Acetobacter pasteurianum. Eur. J Biochem. 112, 541-7. 

Stereoisomers of hopane as the parent hydroearbon of about 100 naturally abundant hopane triterpenes are isolated in small amounts from oil slate and petroleum of various provenanee. Hydroxylated hopanes sueh as (-l-)-6a,22-hopanediol are found to oeeur in some liehens and, assoeiated with (-l-)-22(29)-hopen-6a,2ip-diol, in the roots of Iris missouriensis (Liliaeeae). Neohopanes exemplified by (-l-)-12-neo-hopen-3p-ol from Rhododendron linearifolium (Erieaeeae) rarely oeeur as natural produets. 

Wilkins AL, Ronaldson KJ, Jager PM, Bird PW (1987) A C-NMR Study of some Oxygenated Hopane Triterpenes. Aust J Chem 40 1713 752. Williams DE, Bombuwala K, Lobkovsky E, Dilip de Silva E, Karunaratne V, Allen TM, Clardy J, Andersen RJ (1998) Ambewelamides A and B, Antineoplastic Epidithiapiperazinediones Isolated from the Lichen Usnea sp. Tetrahedron Letters 39 9579... 

Berti et al. found that the tetrasubstituted epoxide derivative (110 equation 44) of the triterpene hopane gave an efficient rearrangement to the ketone (111). 

Ensminger A., van DorsselaerA., Spyckerelle Ch., Albrecht P, Ourisson G. (1973) Pentacyclic triterpenes of the hopane type as ubiquitous geochemical markers origin and significance. In Advances in Organic Geochemistry 1973 (ed. Tissot B., Bienner F.), 245-60. Paris Technip. 

Widespread reports indicate that, in addition to their anti-inflammatory role, triterpenes have other activities. Triterpenoids have been found to possess cytotoxic, antimicrobial and interesting effects on metabolism. Triterpenoids with antitumour activity include oleanane, lanostane, lupane, friedelane, hopane and quassionoid types. Glycyrrhetinic acid has been described as an antiviral, hypolipidemic and anti-atherosclerotic agent. Cucurbitacins B and E, and oleanolic acid possess a potent protective action on the liver, and ganoderic acid and its derivatives have been shown to be inhibitors of cholesterol biosynthesis. Lanostane derivatives, like suberosol, have also been found to inhibit HIV replication in H9 lymphocytes [1,3]. 

The main kind of anti-inflammatory triterpenes isolated have oleanane, ursane, taraxastane, lupane and lanostane skeletons (Table 1). Some minor compounds such as hopane are included in other structural groups. Other anti-inflammatory triterpenes like the different cucurbitacins are not included in this review because of their high toxicity. 

Serratenediol 207 is a member of a recently discovered class of pentacyclic triterpenes,which have a seven-membered C ring and an entirely different skeletal structure from the triterpenoids described above. The compounds may be classified as a modified hopane group with a close biogenetic relationship, serratenediol being chemically interrelated with a-onocerin by a simple transformation. 

The pentacyclic triterpene skeleton hopane is generated by 2,7-, 6,11-, 10,15-, 14,19-, and 18,22-cyclization of the carbenium ion in a fivefold chair conformation (as drawn) arising from regioselective protonation of the 2,3-double bond of squalene (but not of the 2,3-epoxide). This explains why hopanes are usually not hydroxylated in the 3-position. 

Hopanoids naturally occurring derivatives of the pentacyclic triterpene, hopane (Fig.). 

Ikekawa N, Natori S, Ageta H, Iwata K, Matsui M (1965) Gas chromatography of triterpenes. II. Hopane, zeorinane and onocerane groups. Chem Pharm Bull 13 320-325... 

Wenkert E, Baddeley GV, Burfitt IR, Moreno LW (1978) Carbon-13 nuclear magnetic resonance spectroscopy of naturally occurring substances. LVII. Triterpenes related to lupane and hopane. Org Magn Res 11 337-343... 

A novel glycolipid (12) isolated from the extreme thermoacidophile Bacillus acidocaldarius is a 2-acylamino-2-deoxy-j3-D-glucopyranosyl derivative of 1,2,3,4-tetrahydroxypentane linked to hopane (a pentacyclic triterpene) at C-29. Three other glycolipids possess a common structure (13) having the hydroxy-groups of their glycerol residues unsubstituted, or monoacylated, or diacylated. 

Most of the 20 odd triterpenes that have been structurally determined are derived from pentacyclic hopane (94). The exceptions are friedelin (95), epifriedelanol, taraxerene, ursolic acid, and diacetyl pyxinol. 

Allemand (9) used MS-MS for identification of triterpenes and steroids in Evernia prunastri while Shojima et al. (650) reported the MS of about 100 natural and unsaturated pentacyclic triterpenoids, including hopanes and lupanes. 

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