Synthesis of [14C]-labelled dihydropyridine calcium channel entry blockers: Nicardipine-[4-14C] and RS-93522-[4-14C]†

The Hantzsch synthesis has been applied to the general preparation of 4-aryl-dihydropyridines labelled in the metabolically stable 4-position of the dihydropyridine ring. The synthesis is based on the preparation of a key common intermediate, m-nitrobenzaldehyde-[formyl-14C], in high yield from Ba14CO3.