[Cl:1][C:2]1[C:9]([Cl:10])=[CH:8][CH:7]=[CH:6][C:3]=1[CH:4]=O.[C:11]([OH:17])(=[O:16])[CH2:12][C:13]([CH3:15])=O.[NH2:18]/[C:19](/[CH3:27])=[CH:20]\[C:21]([O:23][CH:24]([CH3:26])[CH3:25])=[O:22]>C(O)(C)(C)C>[Cl:1][C:2]1[C:9]([Cl:10])=[CH:8][CH:7]=[CH:6][C:3]=1[CH:4]1[C:20]([C:21]([O:23][CH:24]([CH3:26])[CH3:25])=[O:22])=[C:19]([CH3:27])[NH:18][C:13]([CH3:15])=[C:12]1[C:11]([OH:17])=[O:16]A solution of 2,3-dichlorobenzaldehyde (0.70 g), 3-nitrooxy-2,2-bis(nitrooxymethyl)propyl ester of acetoacetic acid (1.42 g) and isopropyl 3-aminocrotonate (0.57 g) in tert-butyl alcohol (3 ml) was refluxed for 5.5 hours. The resulting mixture was cooled to 25° C., and then concentrated under reduced pressure. The residue obtained was subjected to column chromatography on silica gel (60 g) and eluted with chloroform. The fractions containing the desired compound were collected and evaporated under reduced pressure to give white powders. The powders were recrystallized from a mixture of diethyl ether and diisopropyl ether to give white crystals of 3-nitrooxy-2,2-bis(nitrooxymethyl)propyl ester of 4-(2,3-dichlorophenyl)-5-isopropoxycarbonyl-2,6-dimethyl-1,4-dihydropyridine-3-carboxylic acid (1.36 g), mp 155° to 156.5° C.
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