Application of threo-2-amino-1,2-diphenylethanol as a Resolving Agent for Racemic Carboxylic Acids via Diastereomeric Salt Formation.

The ability of threo-2-amino-1,2-diphenylethanol (1t) as a resolving agent for the enantioseparation of carboxylic acids via diastereomeric salt formation was investigated. Although (-)-1t was not applicable to the enantioseparation of racemic 2-arylalkanoic acids and mandelic acid, enantiomers of tropic acid and 2-halomandelic acids were efficiently separated by salt formation with (-)-1t. This resolving ability was complementary to that of the corresponding erythro-isomer (1e). The hydrogen-bonding patterns and molecular packing mode of the less-soluble diastereomeric salts of (-)-1t were revealed based on the crystallographic analysis.