Technical Procedures for the Syntheses of Carotenoids and Related Compounds from 6‐Oxo‐isophorone: Syntheses of (3 R ,3′ R )‐Zeaxanthin. Part I

Starting from the readily available, optically active (4 R )‐4‐hydroxy‐2,2,6‐trimethylcyclohexanone ( 1 ), a new technical synthesis of (3 R ,3′ R )‐zeaxanthin is described. According to a 2(C 9 + C 6 ) + C 10 = C 40 construction scheme, the ketone 1 was first transformed with ( E )‐3‐methylpent‐2‐en‐4‐yn‐1‐ol ( 5 ) into a C 15 ‐intermediate which, by a three‐step sequence, could be converted into the known olefinic C 15 ‐ Wittig salt 4 . Optimized conditions for the final Wittig reaction of 4 with the C 10 ‐dialdehyde 3 are discussed. Based on 1 , the overall yield of the entire technical process is ca. 40%.