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(R, R)-N, N'-Diisopropyltartramide and its a nalogue show enantioselectivity toward mamy compounds possessing at lest two hydrogen bond sites. The addition of (R, R)-N, N'-diisopropyltartramide to the nonaqueous mobile-phase solvent of a silica gel chromatography as well as the use of a silica-based chiral stationary phase derived from (R, R)-tartramide thus make possible the direct resolution of a wide range of enantiomers. Such enantiomers contain α-hydroxy carbonyl derivatives, β-hydroxy carbonyl derivatives, N-acyl derivatives of primary amines, amino esters, and β-amino alcohols, glutarimides, barbiturates, α-hydroxy ketoximes, bi-β-naphthol and 1, 2-diols. The mode of comp lexation for the observed enantioselction was found to be dual hydrogen bonding between(R, R)-tartramide derivatives and the solute enantiomers to be resolved. This mode of hydrogen bonding leads to the formation of a pair of transient diastereomers differing in stability. The broad scope of application of the (R, R)-tartramide derivative as a chial selector may possibly be due to conformational changes involving the formation and/or scission of intramolecular hydrogen bond (s)at the time of complexation. By such conformational reorganization of the (R, R)-tartramide derivative, this molecule is able to provide dual hydrogen bond sites complementary to those of the versatile enantiomers listed above. Dual hydrogen bonding was observed in an X ray crystal structure of the complex of (R, R)-N, N'-diisopropyltartramide with(S, S)-9, 10-dimethyl-9, 10-dihydrophenanthrene-9, 10-diol. In the complex, intermolecular hydrogen bonds are formed between hydroxyls of the diol and amide carbonyls of (R, R)-tartramide. Dual hydrogen bonds in this complex are characterized by relative orientation of the set of bonding sites of each component showing a twist, rotational sense of which reflects the absolute configuration.

Diret Optical Resolution of Enantiomers by Liquid Chromatography using (R,R)-Tartramide Derivative as a Chiral Selector.