Synthese und Chiralität von (5 R , 6 R )‐5,6‐Dihydro‐β, ψ‐carotin‐5,6‐diol, (5 R , 6 R , 6′ R )‐5,6‐Dihydro‐β, ε‐carotin‐5,6‐diol, (5 S , 6 R )‐5,6‐Epoxy‐5,6‐dihydro‐β, ψ‐carotin und (5 S , 6 R , 6′ R )‐5,6‐Epoxy‐5,6‐dihydro‐β,ε‐carotin

Synthesis and Chirality of (5 R , 6 R )‐5,6‐Dihydro‐β, ψ‐carotene‐5,6‐diol, (5 R , 6 R , 6′ R )‐5,6‐Dihydro‐β, ε‐carotene‐5,6‐diol, (5 S , 6 R )‐5,6‐Epoxy‐5,6‐dihydro‐β,ψ‐carotene and (5 S , 6 R , 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].