The differentiation between enantiotopic carbonyl groups of cyclic meso-dicarboxylic anhydrides has been attained with excellent diastereofacial selectivity with an isomer ratio above 99: 1 by treatment with the lithium salts of sterically hindered chiral N-arylsulfonyl-2- aminoalcohols in the presence of hexamethylphosphoric triamide.
