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) , (+)‐(6 S , 7 E , 9 E )‐abscisic ester 46 , (+)‐(6 S , 7 E , 9 Z )‐abscsic ester 47 , (−)‐(3 S , 7 E , 9 E )‐xanthoxin (49) , (−)‐(3 R , 7 E , 9 E )‐xanthoxin (50) , (3 S , 5 R , 6 S , 3′ S ,5′ R , 6′ S , all‐ E )‐violaxanthin (1) (3 R , 5 R ,6 S ,3′ R ,5′ R ,6′ S , all‐E)‐violaxanthin (55) and their (9 Z ) (see 53 , 57 ), (13 Z ) (see 54 , 58 ), and (15Z) (see 60 ) isomers. The novel violadione ( 61 ) was prepared from 1 by oxidation with DMSO/Ac 2 O. By base treatment, 61 was converted into violadienedione (62) , a potential precursor of carotenoids with phenolic end groups.