合成路线1

The reduction of 2,2-diethoxyacetic acid ethyl ester (I) with NaBH4 in dimethoxyethane gives 2,2-diethoxyethanol (II), which is condensed with ethyl 4-chloroacetoacetate (III) by means of NaH in hot THF to yield ethyl 4-(2,2-diethoxyethoxy)acetoacetate (IV). The condensation of (IV) with 2-chlorobenzaldehyde (V) by means of piperidine in refluxing toluene affords the acrylic ester (VI), which is cyclized with methyl 3-aminocrotonate (VII) in refluxing toluene to provide the dihydropyridine (VIII). The reaction of (VIII) with hydroxylamine in refluxing methanol/water gives the hydroxyimino derivative (IX), which is finally reduced to the target compound by means of H2 over Pd/C in acetic acid or with NaBH4 and NiCl2 in methanol. Alternatively, intermediate dihydropyridine (VIII) can be obtained as follows: The reaction of acetoacetate (IV) with ammonium acetate in refluxing ethanol gives ethyl 3-amino-4-(2,2-diethoxyethoxy)crotonate (X), which is cyclized with methyl 2-(2-chlorobenzylidene)acetoacetate (XI) in refluxing toluene to yield the target intermediate the dihydropyridine (VIII).