Synthesis of single isomers (E or Z) of unsaturated carboxylic acids by the Horner-Wittig reaction

Abstract

Alkyl(diphenyl)phosphine oxides (5) are used to synthesize pure E or Z isomers of unsaturated acids. The keto acids (10), made by two routes, are reduced to hydroxy acids whose crystalline lactones (12) can be separated and purified. Stereospecific elimination of Ph₂PO₂^– gives the unsaturated acids.