SYNTHESIS AND CHIRALITY OF (5R,6R)-5,6-DIHYDRO-BETA,PSI-CAROTENE-5,6-DIOL, (5R,6R,6'R)-5,6-DIHYDRO-BETA,EPSILON-CAROTENE-5,6-DIOL, (5S,6R)-5,6-EPOXY-5,6-DIHYDRO-BETA,PSI-CAROTENE AND (5S,6R6'R)-5,6-EPOXY-5,6-DIHYDRO-BETA,EPSILON-CAROTENE

Synthesis and Chirality of (5R, 6R)‐5,6‐Dihydro‐β, ψ‐carotene‐5,6‐diol, (5R, 6R, 6′R)‐5,6‐Dihydro‐β, ε‐carotene‐5,6‐diol, (5S, 6R)‐5,6‐Epoxy‐5,6‐dihydro‐β,ψ‐carotene and (5S, 6R, 6′R)‐5,6‐Epoxy‐5,6‐dihydro‐β,ε‐carotene Wittig‐condensation of optically active azafrinal (1) with the phosphoranes 3 and 6 derived from all‐(E)‐ψ‐ionol (2) and (+)‐(R)‐α‐ionol (5) leads to the crystalline and optically active carotenoid diols 4 and 7, respectively. The latter behave much more like carotene hydrocarbons despite the presence of two hydroxylfunctions. Conversion to the optically active epoxides 8 and 9, respectively, is smoothly achieved by reaction with the sulfurane reagent of Martin [3]. These syntheses establish the absolute configurations of the title compounds since that of azafrin is known [2]. Copyright © 1979 Verlag GmbH & Co. KGaA, Weinheim