Vancomycin-based chiral stationary phases for micro-column liquid chromatography

Vancomycin selectively immobilized to silica via either one of its two amino groups has been investigated and compared with columns made from native vancomycin. The chemical modification of vancomycin prior to immobilization involved protection of one amino group as a 9-fluorenylmethyl carbamate. The immobilization and the subsequent cleavage of the protecting group was performed on-column. The types of compounds that can be separated with the vancomycin chiral stationary phases resemble those separated previously by capillary electrophoresis and thin-layer chromatography. The protected chiral stationary phases were also investigated and in some cases very high enantioselectivity were obtained. One example of this is a separation of thalidomide with an oc-value as high as 5.4. The soft immobilization procedure preserves the structure of native vancomycin, in contrast to other approaches. Good repeatability and stability of the columns have also been obtained. (C) 1999 Wiley-Liss, Inc.