Pentacyclic triterpenes lupeol

The direct, one-step pentacyclization of (S)-2,3-oxidosqualene to the pentacyclic triterpene lupeol is a remarkable example of biosynthetic efficiency. Lupeol has been synthesized... 

B. Buchele, W. Zugmaier, T. Simmet, Analysis of pentacyclic triterpenic acids from frankin cense gum resins and related phytopharmaceuticals by high performance liquid chromatogra phy. Identification of lupeolic acid, a novel pentacyclic triterpene, Journal of Chromatography B, 791,21 30(2003). 

The betulinic acid level in the E. florida leaves increased significantly in the May, June, Jully (autumn - winter) and, September, October and November (winter) which was mainly due to the accumulation of this compound in vegetal tissue. Some authors related with the pentacyclic triterpenes, just as betulinic, acid ursolic, acid, p-amyrine and lupeol, are supposed to be toxic to insects, due to their ability to inhibit acyl chain packing in the lipid bilayers of the insect membranes [Rodriguez et al, 1997 Prades et al., 2011]. 

Lupeol a pentacyclic, triterpene alcohol, M, 426.73, m.p. 215°C, [al + 27.2 (c = 4.8 in CHa,). L. has a Sa-lnpane ring system. It occurs free, esteified and as the aglycon of triterpene Saponins (see) in many plants. It has been found, e.g. in the latex if Ficus spp, in the seed coats of the yellow lupin Lupinus lu-teus) and in the leaves of mistletoe. It has also been detected in the cocoons of the silk-worm, Bombyx mori. 

The pentacyclic triterpenes either comprise five anellated cyclohexane rings (oleanane type) or four cyclohexane rings connected with a cyclopentane ring (lupeol type. Fig. 114). These skeletons may carry a hydroxy group at C-3 (an exception are hopanoid-type compounds) and methyl groups at the positions 4, 8, 10, 14, 17, and 20 and in the case of lupeol-type compounds an isopropyl group at C-19. 

Apart from the function of X-group itself, this mechanism also necessarily differs in stereochemical detail. It will be noted that the lupeol-like intermediate (7), in order to set the stage for the following anti-parallel rearrangements (8-> 9a and 9b l0), has the unnatural stereochemistry at C19 (ocH). Thus, this proposal suggests that lupeol (348) does not lie along the same biogenetic path as the other pentacyclic triterpenes. 

In C.halimii leaf wax triterpenoids were found in the very high amount of 72%,beside the wax lipids. The free triterpenols dominated with about 62%. Identified could be B-amyrin, a-amyrin and lupeol. In small amounts esters of B-amyrin and a-amyrin containing long chain fatty acids were found. Again triterpene ketones were isolated and detected with the aid of GC/MS. In this wax lupenone was present and also one other ketone named fridelanone in the remarkable amount of about 12%. They could be reduced to the corresponding alcohols. Fridelanone and fride-lanol have a pentacyclic structure without any double bond. Therefore these substances showed quite different Rf values in TLC and no colour reaction with carbazole (3)(Fig.l). 

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