Dienolether condensations - A powerful tool in carotenoid synthesis

Abstract

The catalytic dienolether condensation reactions, discovered by Nazarov and Makin in 1958, are of special interest in the carotenoid field for chain extension by five carbon atoms. In this paper, new developments in the synthesis of apoesters and apocarotenals using vinyl ketene acetals and dienolethers, respectively, as C5-building blocks are discussed. New 'Wittig-free' routes to astaxanthin and canthaxanthin applying these Lewis acid-catalysed dienolether condensation reactions are described. © 1999 IUPAC.