of the ethyleneketals 7a–7d of the latter furnishes mixtures of the corresponding diastereomeric monoesters 8 and10. The ethoxycarbonyl groups of the trans esters 8 are more reactive than those of the cis isomers 10. This permits, under appropriate conditions, selective alkaline hydrolysis and NaBH4 reduction of the trans esters 8 in the presence of the cis esters 10. Reduction of the cis ester 10c