Synthesis of buf-20(21)-enolides and bufa-20,22-dienolides

Abstract

A practical three-step procedure for converting an aldehyde to a 5-substituted dihydro-2-pyrone or by an additional step to the corresponding 2-pyrone has been summarized. Synthesis of 2-pyrone 5, buf-20(21)-enolide 9 (and Δ 5 -derivative) and bufadienolide 10 were used for illustration.