Studies on the constituents of asclepiadaceae plants. LI. Oxidation at the 18-methyl group of C/D-cis-pregnane type steroids and 13C-nuclear magnetic resonance spectra of 18-oxygenated pregnanes and related compounds.

Abstract

Four 18-oxygenated pregnane-type steroids ; 18, 20-epoxypregn-5-en-3β-ol acetate (III), 18, 20-epoxy-isolineolon cyclic sulfite (VIII), 18, 20-epoxy-deacyl condurangogenin C (XVIII), and 18, 20-epoxy-20-epideacyl condurangogenin C (XXI) were synthesized, and their structures were established by chemical and spectral studies. A remarkable difference in ¹³C-nuclear magnetic resonance chemical shifts between 20R-and 20S-hydroxy-C/D-cis-pregnane-type steroids was found.