Unprecedented stability of δ-lactones with axial substituents rather than equatorial ones; comparison with the Prelog–Djerassi lactone derivative

Abstract

A 1 : 1 mixture of the trisubstituted δ-lactones 11a and 11b was subjected to thermodynamically equilibrated conditions to give predominantly 11b with axial substituents rather than 11a with all equatorial ones, in contrast to the Prelog–Djerassi lactone derivatives 3a and 3b, and, further surprisingly, it has been found that the disubstituted lactone 10 also adopts a chair conformation with axial substituents.