Separation of enantiomers on diastereomeric right- and left-handed helical poly(phenyl isocyanide)s bearing L-alanine pendants immobilized on silica gel by HPLC

Diastereomeric left- and right-handed helical polyisocyanides composed of L-alanine-bound phenyl isocyanides were prepared. The helical polymers with a narrow molecular weight distribution were immobilized on a silica gel support via chemical bonding and their optical resolution abilities were evaluated as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). The CSP prepared from the left- handed helical polyisocyanide resolved racemic cyclic ether and carbonyl compounds and cyclic dianilides and dibenzamides, whereas the right-handed helical polyisocyanide-based CSP showed a rather complementary chiral recognition ability and specifically resolved racemic metal acetylacetonate complexes, which were not separated on the former CSP at all. Additionally, the elution order of some enantiomers was reversed on the CSPs, thus indicating that the macromolecular helicity of the L-alanine-bound-polyisocyanides played a critical role in the enantioselectivity and elution order of the enantiomers.