STUDIES DIRECTED TOWARD THE SYNTHESIS OF PHOMENOIC ACID .1. ENANTIOSELECTIVE SYNTHESIS OF THE C(1)-TO-C(6) SEGMENT

Based on a retrosynthetic analysis, a concept for the synthesis of all stereoisomers of the C(1)-to-C(6) segment of phomenoic acid has been developed. Both enantiomers of the chiral synthon 9 were prepared star ting from rac-epoxy-diester 10. They were converted to both enantiomer s of the epoxyalcohol, 16 and 21, respectively, using Sharpless epoxyd ation. They served as building blocks for the synthesis of the tetrol derivatives 20 and 22, respectively. All four stereoisomers were obtai ned in optically pure form. They contain the correct assembly of prote cted functional groups, allowing selective deprotection in view of fur ther transformations.