Abstract
In an attempt toward the synthesis of 20 (S)-protopanaxadiol (I) from dammarenediol-II (V), the introduction of a hydroxy function to C-12 of the dammarane skeletone has been studied. A solution of p-nitrobenzoate (IX) of 3-epi-dammaranediol-I (VIII) in tert-BuOH was irradiated for 40 hr and the products were saponified to give 17-octakis-nordammarane-3α, 17β-diol (X). From the crude irradiation products, 6-methyl-2-heptanone (XII) was isolated and identifiel. Whereas, the irradiation of p-nitrophenylacetate (XIX) of 3-epi-dammaranediol-II (XVI) under the similar condition followed by saponification yielded the 12-hydroxy compound (XX). This was converted into betulafolienetriol (XXI) and 20 (S)-protopanaxadiol (I) furnishing the synthesis of the Ginseng sapogenin.
