Studies on Anthelmintics. XXIX

New Rearrangement of Santonin. II. Application of the Rearrangement to Some Synthetic Intermediates of Santonins

Abstract

Treatment of several intermediates of santonin synthesis, possessing the trans-lactone ring, with dimethylformamide containing hydrogen halide results in isomerization of the lactone ring to cis-form and the corresponding isomers are formed. This rearrangement reaction was utilized in clarifying the steric configuration of the two kinds of monoesters (XX and XXIV), obtained by partial saponification of ethyl 11-ethoxycarbonyl-3-oxoeusanton-4-enate (XI), and the cis-lactonic esters derived from them.