Abstract
The chemical properties of the side chain of dammarane type triterpenes are discussed. Dehydrochlorination of the chloro compounds (II and IV) derived from ginsenosides Rb1, Rb2 and Rc or their prosapogenins by the conc. HCl hydrolysis afforded the compounds having the side chain with isopropylidene (I or III) and isopropenyl double bond (VII or V). The ratio of the occurrence of the two types of double bond systems depends on the dehydrochlorination reagents used. On treating with BF3 etherate in ether, 20 (R)-protopanaxadiol (III) gave isodehydro-protopanaxadiol (VIII), which was also obtained as an artifact from the crude hydrolysate of Ginseng saponins. On treating with NBS betulafolienetriol (VI) yielded a bromo compound, C30H51O3Br, whose stereochemical structure was finally established to be XVI by X-ray crystallographic analysis. A similar compound (XVIII) was obtained from 20 (R)-protopanaxadiol (III) with NBS. The mechanism of the bromination reaction is elucidated.
