Total Synthesis of 1,2,5,6-Tetrahydro-2,6-cyclo-γ-carotene-1,5-diol, an Oxidation Product of γ-Carotene

Abstract

1,2,5,6-Tetrahydro-2,6-cyclo-γ-carotene-1,5-diol, an oxidation product of the pro-vitamin A food carotenoid γ-carotene, was synthesized by a C 15 + C 10 + C 15 double Wittig coupling strategy. The total synthesis involved a key C 15 -dihydroxyaldehyde synthon derived from (E/Z)-citral, a protected C 10 -Wittig salt, and (β-ionylideneethyl)triphenylphosphonium chloride (C 15 -Wittig salt). This synthetic route provides novel access to an oxidation product of γ-carotene that could be potentially formed in humans or biological systems as a consequence of metabolic oxidation.