Synthese von enantiomerenreinen Violaxanthinen und verwandten Verbindungen

Syntheses of Enantiomerically Pure Violaxanthins and Related Compounds The epoxides 16 and ent‐16, prepared by Sharpless‐Katsuki oxidation of 15 in excellent yield and very high enantiomeric purity, were used as synthons for the preparation of (+)‐(S)‐didehydrovomifoliol (45), (+)‐(6S, 7E, 9E)‐abscisic ester 46, (+)‐(6S, 7E, 9Z)‐abscsic ester 47, (−)‐(3S, 7E, 9E)‐xanthoxin (49), (−)‐(3R, 7E, 9E)‐xanthoxin (50), (3S, 5R, 6S, 3′S,5′R, 6′S, all‐E)‐violaxanthin (1) (3R, 5R,6S,3′R,5′R,6′S, all‐E)‐violaxanthin (55) and their (9Z) (see 53, 57), (13Z) (see 54, 58), and (15Z) (see 60) isomers. The novel violadione (61) was prepared from 1 by oxidation with DMSO/Ac2O. By base treatment, 61 was converted into violadienedione (62), a potential precursor of carotenoids with phenolic end groups.