Straightforward synthesis of unnatural poly-oxygenated steroid sapogenins

Abstract

Saponins and their biosynthetic intermediates, sapogenins, display a variety of biological activities of interest to the pharmaceutical, cosmetic and food sectors. Three unnatural steroid sapogenins bearing oxygenated functions in rings A, B and F were prepared following a straightforward synthetic protocol that comprises the installation of a carbonyl function in ring F, a two-step, one-pot generation of a ketol in A,B rings, and the addition of a cis-diol in ring A by osmylation. Unambiguous NMR characterization is provided.