The Hantzsch synthesis of nifedipine

Nifedipine is a 1,4-dihydropyridine that blocks the calcium channels of vascular smooth muscle and is used against hypertension and angina. It is prepared in a single step by the Hantzsch synthesis: 2-nitrobenzaldehyde, two equivalents of methyl acetoacetate and ammonia are heated in methanol.

Here the dihydropyridine is not oxidized, because it is the active form. In fact, nifedipine is light-sensitive: it is oxidized to the inactive aromatic pyridine, which is why it is packaged protected from light. Varying the aldehyde and the esters gives the whole family of “dipines”, such as amlodipine.