Pentacyclic triterpenes betulinic acid

Although not without some synthetic challenges due to the sterically demanding and rigid framework of the pentacyclic triterpene, betulinic acid 1... 

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]. 

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