Synthesis of 3β,14β,19-Oxygenated Cardenolides

Abstract

The synthesis of 3β,14β,19-oxygenated and of 3β,19-oxygenated-14-dehydro cardenolides from the bulk steroid pregnenolone acetate 1a is reported. The 19-oxygenated cardenolides which have been prepared include coroglaucigenin esters 4e and 4f and corotoxigenin acetate 4g. Coroglaucigenin and corotoxigenin occur in nature as glycosides in a number of plant species. In the synthetic scheme developed, successive transformations of the 3β-acetoxy-10β-methyl-5-ene moiety of 1a afford 19-hydroxy- or acyloxy-14-enes via 19-hydroxy-8(14)-enes and 8,19-oxido-14-enes.