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


  • Dedicated to Dr. Otto Isler on the occasion of his 80th birthday


Starting from the readily available, optically active (4R)-4-hydroxy-2,2,6-trimethylcyclohexanone (1), a new technical synthesis of (3R,3′R)-zeaxanthin is described. According to a 2(C9 + C6) + C10 = C40 construction scheme, the ketone 1 was first transformed with (E)-3-methylpent-2-en-4-yn-1-ol (5) into a C15-intermediate which, by a three-step sequence, could be converted into the known olefinic C15-Wittig salt 4. Optimized conditions for the final Wittig reaction of 4 with the C10-dialdehyde 3 are discussed. Based on 1, the overall yield of the entire technical process is ca. 40%.