DIRECT ISOMERIC SEPARATION OF A 3-HYDROXYPROLINE-CONTAINING PRODRUG, L-693989, BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH A POROUS GRAPHITIC CARBON COLUMN

The use of high-performance liquid chromatography (HPLC) with a porous graphitic carbon (Hypercarb) column for the direct separation of a po sitional isomer of L-693 989, a 3-hydroxyproline-containing prodrug, i s described. The isomer peak was isolated by HPLC and analyzed by mass spectrometry and proton nuclear magnetic resonance spectroscopy. An a uthentic sample of the isomer was also synthesized for chromatographic comparison. The results confirm that the peak in question is a 4-hydr oxyproline isomer which is difficult to separate from L693 989 compoun d with the silica-based reversed-phase columns. The observed chromatog raphic elution supports the retention mechanism based on the unique el ectronic donor-acceptor interaction between the lone-pair electrons of the analyte (donor) and the delocalized electron conduction bands on the graphitized carbon stationary phase (acceptor).