[CH3:1][C:2]1[NH:3][C:4]([CH3:24])=[C:5]([C:18]([O:20][CH2:21][CH2:22][OH:23])=[O:19])[CH:6]([C:11]2[CH:16]=[CH:15][CH:14]=[CH:13][C:12]=2[Cl:17])[C:7]=1[N+:8]([O-:10])=[O:9].[OH2:25].N1[CH:31]=[CH:30]C=CC=1>C(OC(=O)C)(=O)C>[CH3:1][C:2]1[NH:3][C:4]([CH3:24])=[C:5]([C:18]([O:20][CH2:21][CH2:22][O:23][C:30](=[O:25])[CH3:31])=[O:19])[CH:6]([C:11]2[CH:16]=[CH:15][CH:14]=[CH:13][C:12]=2[Cl:17])[C:7]=1[N+:8]([O-:10])=[O:9]1 g of β-hydroxyethyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-chlorophenyl)-pyridine-5-carboxylate is stirred overnight in a mixture of 15 ml of pyridine and 15 ml of acetic anhydride. The mixture is poured into water and extracted with ethyl acetate and the extract is washed with 1 N HCl, water, sodium bicarbonate solution and water again, dried and concentrated. The evaporation residue is crystallized with ethanol, filtered off with suction and washed with ethanol. 800 mg of a yellow-coloured compound of melting point 166° C. which is identical to the compound from Preparation Example 1, process variant A are obtained.
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