Photochemical transformation of bufadienolide into 14β,21-epoxycholanes via photolytic methanolysis

Abstract

A naturally occurring bufadienolide, proscillaridin 1a, and its aglycone, scillarenin 1b, were subjected to photolysis in MeOH with a high-pressure mercury are lamp to afford novel 14β, 21-epoxy-21-methoxycholadienes 2a–4a and 2b–4b and 14β,21-epoxy -22-methoxycholadienes 5a, 5b, 6a and 6b, along with 14β,21-epoxycholatrienes 7a and 7b. These structures were elucidated from spectroscopical evidence including NOE experiments.