Chromatographic separation of the diastereomers of a dihydropyridine-type calcium channel antagonist as the bis-3,5-dinitrobenzoates.

The diastereomeric components of the calcium channel antagonist RS-93522-004 are separated as the bis-3,5-dinitrobenzoate ester by reversed-phase high-performance liquid chromatography. The diastereomer ratio determination is shown to be precise, accurate and sensitive, and is not affected by the reaction yield of the derivatization with 3,5-dinitrobenzoyl chloride. The four individual stereoisomers of RS-93522-004 were independently shown to have equal reactivity toward 3,5-dinitrobenzoyl chloride.