ENANTIOMERIC DERIVATIZATION FOR BIOMEDICAL CHROMATOGRAPHY

Derivatization reactions aimed at creating the basis for the chromatog raphic resolution of biologically and pharmaceutically important enant iomers are reviewed, with emphasis on the literature published in the last 10 years. Three main aspects of chiral derivatization are discuss ed. (a) Enantiomers containing suitable functional groups (amino, carb oxyl, hydroxyl, epoxy, etc.) are transformed into covalently bonded di astereomeric derivatives using homochiral derivatizing agents. The dia stereomers formed (esters, amides, urethanes, urea and thiourea, etc., derivatives) can be separated on achiral stationary phases. The deriv atization reactions often afford further advantages, such as the impro vement of chromatographic properties and the detectability of the solu tes using UV and fluorimetric detectors. (b) Covalent but achiral deri vatization is often necessary even with the use of chiral stationary p hases enabling in principle direct enantioseparations (Pirkle-type col umns, cyclodextrin-bonded phases, glycoprotein column and functionaliz ed cellulose columns). The main goals of these derivatization reaction s (which are analogous to those discussed above), are to introduce fun ctional groups into the molecule of the enantiomers that improve the p ossibilities for chiral interactions or block functional groups to avo id non-specific interactions. (c) In the broader sense, the dynamic fo rmation of diastereomers using chiral mobile phase additives (cyclodex trins, various reagents to form diastereomeric ion pairs, adducts, mix ed metal complexes) can also be considered to be chiral derivatization reactions and is therefore briefly discussed also.