Stereoselective Reactions. XII. : Synthesis of Antitumor-Active Steganacin Analogs, Picrosteganol and Epipicrosteganol, by Selective Isomerization

Abstract

New steganacin analogs with definite absolute configurations, (-)-picro- and (-)-epipicrosteganol, were synthesized by isomerization of (-)-steganol and (-)-episteganol, respectively, at the α-position to the lactone carbonyl. The structure of (-)-epipicrosteganol was confirmed by X-ray crystallographic analysis. Selective epimerization at the C-4 benzylic position was observed upon acidic treatment of (-)-steganacin, giving (-)-episteganacin.