Stereoselectivity at alpha-adrenoreceptor subtypes: observations with the enantiomers of WB 4101 separated through their amides of N-tosyl-(S)-proline.

We present a chromatographic method for the separation and determination of the optical purity of the enantiomers of WB 4101 [(+/-)-1], one of the most potent and selective alpha 1-adrenoreceptor antagonists. (+/-)-1 was converted into the amide of N-tosyl-(S)-proline. The two diastereoisomers were separated on silica gel and analysed by HPLC reversed phase. The analytical method described is both accurate and sensitive and allows the optical purity to be determined at very low concentrations and to obtain WB 4101 enantiomers with a purity of more than 99.95%.