Preparation of the enantiomers of 19-epoxy docosahexaenoic acids and their 4-hydroxy derivatives

Abstract By the action of NBS in aq. DME, dl -19-bromo-20-hydroxy-DHA methyl ester 5 was prepared, which was effectively resolved by lipase PS and vinyl acetate in the presence of a thiacrown ether to give 7 and 8 , each being transformed into the corresponding epoxides, 1 and 2 , respectively. The absolute configuration of 8 was established by the Kusumi–Moscher method. For the purpose of biological evaluation, both epoxides were converted to the γ-lactones 3 and their 4-hydroxy derivatives 4 .