Protopanaxatriol oxide

The structure of (58) was further confirmed by its preparation from (36) peracid oxidation of the side chain double bond of (36) gave a mixture of very unstable epoxides epimeric at 24, which underwent spontaneously cyclization to (58) and its c-24 epimer (66). In the C-NMR spectrum of the latter, c-24 and the other side chain carbons exhibited shifts essentially identical with those of (62), thus substantiating the assignment of chirality at c-24. The names 20(S)-protopanaxatriol-oxide I and II were proposed for (58) and (66). 

As mentioned in Chapter VIII-4, rhizomes of P. japonicus var. major yielded the ocotillol type saponins, majonosides-Rl and -R2, the aglycone of both of which was identical with 20(S)-protopanaxatriol-oxide II (66), the c-24 epimer of (58) 105). 

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