Syntheses of [6-14C] and [5-carboxy, 6-14C2]nitrendipine

[6‐14C]Nitrendipine synthesis started from barium[14]carbonate, which was converted to [1‐14C]acetyl chloride. The acid chloride was condensed with Meldrum's acid (2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione). The resulting intermediate was treated with boiling methanol to give methyl [3‐14C]acetoacetate. The reaction with gaseous ammonia in toluene yielded the corresponding methyl 3‐amino[3‐14C]crotonate which was condensed with ethyl 2‐(3‐nitro‐benzylidene) acetoacetate to obtain [6–14C]nitrendipine. [5‐carboxy, 6‐14C2]Nitrendipine was synthesized by an analogous procedure starting from methyl [1,3‐14C2]acetoacetate.