Structure of dregeanin and rohitukin, limonoids from the subfamily Melioideae of the family Meliaceae. An unusually high absorption frequency for a six-membered lactone ring

Abstract

A new group of limonoids, characterised by the possession of a seven-membered lactone ring A, a secoring B, and a five-membered carbocyclic ring D, has been discovered in the sub-family Meliodieae; a C(1)-C(7) lactone occurring in certain of these is characterised by an unusually high frequency carbonyl absorption in the i.r. spectra.