Taraxerane

Two new taraxeranes (190) and (191) have been isolated from Quercus bambusaefolia. ° Isomultiflorenone (192) and isomultiflorenol acetate (193) are new natural products from Cucurbita lundelliana and Vernonia fasciculata respectively. Studies on the allylic oxidation and bromination of taraxeryl acetate (194) and on the Lewis acid-catalysed rearrangement of (194) and friedelanol have been reported. 

The structure of retigeradiol, from the lichen Lobaria retigera, has been revised to stictane-3j8,22a-diol (211). It was originally thought to be taraxerane-3/3,19/3-diol. The ketol previously isolated from Centraria nivalis is probably 22a-hydroxystictan-3-one (212). ... 

Twenty-three triterpenoid hydrocarbons isolated from ferns were screened [67]. The following eight exhibited strong inhibitory effects at lxlO2 mol ratio compound/TPA with >80% viability of Raji cells [67]. They are multiflor-8-ene (220 45%), multiflor-9(ll)-ene (228 41%), taraxastane (237 43%), taraxerane (241 37%), glutin-5(10)-ene (244 52%), hop-17(2l)-ene (275 51%), neohop-13(18)-ene (277 37%), and neohop-12-ene (278 37%). It should be mentioned that the inhibitory... 

Through a series of cyclizations, squalene oxide (C30) affords lanosterol in animals and fungi and cycloartenol in plants (Fig. 19). In both instances, the intermediate is a protosteryl cation that can also undergo a series of Wagner-Meerwein rearrangements to afford the cytotoxic cucurbitacins of melons and cucumbers. Squalene oxide in a chair-chair-chair-boat conformation yields the dammarenyl cation, a parent of numerous triterpene skeleta (e.g., lupane, oleanane, ursane, and taraxerane) contained in the saponins found in many foodstuffs, in soaps, and in several... 

Several taraxerane derivatives have been reported. These include taraxer-14-ene-3/3,29-diol (127), the diacetate (128), 29-hydroxytaraxer-14-en-3-one (129), the acetate (130), 14a-hydroxytaraxeran-3-one (131), and taraxerane-3/3,14a-diol (132) from the stems of Lithocarpus cornea and epitaraxeryl acetate from Melaleuca leucadendron ° ... 

This Reporter prefers to name these compounds as derivatives of taraxastane rather than taraxane since this is less confusing with respect to the taraxerane group. 

Among the compounds reported, mainly oleanes, lupanes, friedo-oleanes, glutinanes, taraxeranes, ursanes and dammaranes had been isolated from Celastraceae species. 

The full papers on the photo-oxidation process utilized in the transformation of spergulagenicacid into euptelogenin have been published (see Vol. l,p. 193). Application of this reaction to erythrodiol (145) afforded the lla,12a-epoxy-13)3,28-oxide (146) together with the rearranged lla,12a-epoxy-taraxerane (147). 

Taraxeral (14-taraxeren-3jS-ol). Formula, see triterpenes. C30H50O, Mr 426.73, mp. 282-283 °C, [ajp -t0.7° (CHCI3). T. is a triterpene widely distribute in the plant kingdom, isolated for the first time in 1923 from the bark of gray alder (Alntts incana). T. also occurs in the roots of dandelion (Taraxacum officinale), in various alder species, rhododendron species, and Euphoibiaceae, as well as in some lichens. T. is derived from the taraxerane skeleton and has antigastritic properties. 

Taraxarol, alnulin, skimmioL- a simple, unsaturated, pentacyclic triterpene alcohol, M, 426.73, m.p. 285 °C, [a]i,-H3°, structurally a derivative of the patent hydrocarbon, 5a-taraxerane. It occurs in many members of the Compositae, e. g.dandelion (Taraxa-um officinale), and in alder (Alnus) bark. 

Fig. 8.1.32. Biogenesis of taraxerane, multiflorane, glutinane, and fridelane types...

Ten new metabolites (507—516), isolated from Pseudocyphellaria species by Corbett, Wilkins and co-workers (57), provide the first examples of this new group of triterpenoids. The structures of these metabolites followed primarily from a detailed comparison of the H-n.m. r. spectra with those of other triterpenoid groups. Corbett and coworkers had previously synthesized a number of the parent triterpanes, 18a-oleanane (5 ), 17aH-hopane (55), 17aH-moretane (55) and 14a-taraxerane (55), by methods similar to those exemplified for stictane (Scheme 66). Thus oxidation of the alcohol (516) gave the diketone (517) which upon Wolff-Kishner reduction yielded the parent stictane (518). The physical and spectroscopic properties of this triterpane confirmed the novelty of this group of compounds. 

Carpenter RC, Sotheeswaran S, Sultanbawa MUS, Ternai B (1980) C-NMR Studies of some Lupane and Taraxerane Triterpenes. Org Magn 14 462... 

Taraxeranes, Multiflorane, Glutinanes, Friedelanes, Isoursane, Phyllanthane,... 

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