Reversal of enantiomeric elution order on macrocyclic glycopeptide chiral stationary phases

The macrocyclic glycopeptides, vancomycin, teicoplanin, and ristocetin A ar e naturally occurring chiral molecules that have been developed into one of the most useful classes of chiral stationary phases (CSPs) for HPLC, Since these chiral selectors are structurally related, they tend to have similar , but not identical, enantioselectivities for most compounds. CSPs, of this type, with opposite enantioselectivities are rare. Two exceptions have bee n found to this. The oxazolidiones (starting materials for asymmetric synth esis) and dansyl amino acids all show a reversal in enantioselective retent ion on one of these three related CSPs. By using the HPLC assays developed for these compounds, the levels of enantiomeric impurities can be measured down to similar to0.01%. The enantiomeric purity of commercial oxazolidione s was determined.