Preparation of cis Carotenoids by Total Synthesis

Abstract

The most brilliant achievement in polyene chemistry during the last decade has been the total synthesis of certain naturally occurring carotenoids and of some analogs and homologs that have not yet been found in plants. The synthesis of β-carotene was announced in 1950 by Karrer and Eugster (226), almost simultaneously by Inhoffen, Bohlmann, Bartram and Pommer (184), and somewhat later by Milas et al. (316). Since this breakthrough the new field has been broadened and deepened by the research groups of Karrer, Inhoffen, Isler, Weedon, and others [cf. also Surmatis et al. (428)]. The pertinent literature till 1952 has been discussed in detail by Inhoffen and Siemer (193); for a brief survey cf. Karrer (223). In 1957 Isler and Zeller’s excellent review has appeared (210). The present report, which of course cannot do justice to the authors active in this fascinating field, will be restricted to a few stereo chemically important aspects of carotenoid synthesis.