HIGHLY SELECTIVE CHIRALLY TEMPLATED ISOMUNCHNONE CYCLOADDITIONS OF ACHIRAL ALDEHYDES - SYNTHESIS OF AN ENANTIOPURE ALPHA,BETA-DIHYDROXYACID

Additions of p-nitro- and p-methoxybenzaldehyde to isomunchnone deriva tives of (5S)-phenyloxazin-3-one and -2,3-dione led to corresponding a dducts (3,4,6) with excellent diastereofacial and exo-selectivity, Hyd rolysis and subsequent cleavage of adduct 3 permitted recovery of the original template and furnished dihydroxyacid 9 that was transformed i nto the known ethyl ester 10. Comparison of its optical rotation with the literature value confirmed its high optical purity. (C) 1997 Elsev ier Science Ltd.