合成路线1

Iganidipine can be obtained by two similar ways: 1) The condensation of 1-(tert-butoxycarbonyl)piperazine (I) with isobutyraldehyde (II) and formaldehyde in acetic acid gives 3-[4-(tert-butoxycarbonyl)piperazin-1-yl]-2,2-dimethylpropionaldehyde (III), which is reduced with NaBH4 in isopropanol to the corresponding alcohol (IV). The condensation of (IV) with diketene (V) by mens of dimethylaminopyridine (DMAP) in dichloromethane affords the acetoacetic ester (VI), which is cyclized with 3-nitrobenzaldehyde (VII) and methyl 3-aminocrotonate (VIII) in refluxing isopropanol to give the protected dihydropyridine (IX). The elimination of the tert-butoxycarbonyl group of (IX) with HCl in ethanol yields dihydropyridine (X), which is finally alkylated with allyl chloride (XI) and triethylamine in hot THF. 2) The condensation of 3-(4-allylpiperazin-1-yl)-2,2-dimethylpropanol (XII) with diketene (V) in dichloromethane gives the corresponding acetoacetic ester (XIII), which is treated with dry NH3 in methanol to yield the 3-aminocrotonic ester (XIV). Finally, this compound is cyclized with 2-(3-nitrobenzylidene)acetoacetic acid methyl ester (XV) in hot isopropanol.