[CH3:1][C:2]1NC(C)=C(C(OC(C)C)=O)[CH:4]([C:15]2[C:20]3=[N:21][O:22][N:23]=[C:19]3[CH:18]=[CH:17][CH:16]=2)[C:3]=1[C:24]([O:26][CH3:27])=[O:25].N1[O:29]N=C2C(C=O)=CC=CC=12.C(OC)(=O)CC(C)=O.N1CCCCC1>C(OC(C)C)(C)C.C(O)(=O)C>[CH3:27][O:26][C:24](=[O:25])[C:3]([C:2](=[O:29])[CH3:1])=[CH:4][C:15]1[C:20]2=[N:21][O:22][N:23]=[C:19]2[CH:18]=[CH:17][CH:16]=1
To achieve the afore-mentioned objects, the present invention provides for a process for the manufacture of the Isradipine which, involves two steps. In the first step 2,1,3-benzoxadiazole-4-carboxaldehyde is reacted with methyl acetoacetate in the presence of acetic acid and piperidine in diisopropyl ether. The product 2-acetyl-3-benzofurazan-4-yl-acrylic acid methyl ester is isolated and purified to get substantially high purity product with less than 0.3% 2,1,3-benzoxadiazole-4-carboxaldehyde content present in the purified product. In the second step the purified intermediate 2-acetyl-3-benzofurazan-4-yl-acrylic acid methyl ester is reacted with isopropyl-β-aminocrotonate in ethanol at 25 to 35° C. The crude Isradipine is crystallised from ethanol to get pure Isradipine having substantially higher purity and containing lower amount of the symmetrical ester isomers (III) and (IV).
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