STRUCTURAL ASPECTS OF DIASTEREOMERIC DISCRIMINATION. Edward J. Valente, Christopher Miller, Gerard Ruggiero, Department of Chemistry, Mississippi College, Clinton, MS 39058, and Drake S. Eggleston, Department of Physical and Structural Chemistry, SmithKline Beecham, Co., King of Prussia, PA, 19401

Systems showing two kinds of diastereoselective solubility disparities are described. In the system of warfarin and its derivatives and (+)-quinidine, a pattern in resolution success (= formation of a separable salt) as a function of warfarin substituent position has been found. Warfarin with a single phenyl substituent in the 3'- or 4'-positions and 2',3'-, 3',4'- disubstituted warfarins usually form less-soluble salts between their (-)(S)-isomers and (+)-quinidine; their diastereomers are oils. The solid state structures of the less-soluble salts show that a single, strong N-H...O interaction linking warfarin enolate anions with protonated quinuclidine of quinidine. Packing motifs are remarkably similar over the range of substituents demonstrating that how a dominant interion interaction may serve as the basis for successful resolutions within a series of related substances. In the system of mandelic acid and its phenyl substituted derivatives and (-)-ephedrine, both less-soluble and more-soluble salts can be isolated from 95% ethanol. The uniformly unsolvated salts vary from little to strong solubility disparities in aqueous ethanol, properties which correlate with their temperatures and heats of fusion. Six kinds of packing motifs have been found. These demonstrate a considerable range in packing efficiency while retaining correlations with configuration of the mandelate anion. Interion H-bonding type is one of the important organizing principles. Links between some of the packing groups have been found in the form of polymorphs and solid-solid phase transitions in some of the salt phases.