Biomimetic transformations of the biogenetic key intermediate secologanin

Oxidation of secologanin tetraacetate 2 with osmium tetroxide afforded 45% of the bicyclic hemiacetal 3, which gave secogalioside tetraacetate 8 in a 29% yield and in addition 62% of the tricyclic acetal 6 by treatment with the N -chlorosuccinimide dimethyl sulfide complex. Sovolysis of 8 yielded 60% of secogalioside 9.