[CH3:1][C:2]1[NH:7][C:6]([CH3:8])=[C:5]([C:9]([O:11][CH3:12])=[O:10])[CH:4]([C:13]2[CH:14]=[CH:15][CH:16]=[CH:17][C:18]=2[N+:19]([O-:21])=[O:20])[C:3]=1[C:22]([O:24][CH3:25])=[O:23].[H-].[Na+].CI.[C:30](OCC)(=O)C>O1CCCC1>[CH3:1][C:2]1[N:7]([CH3:30])[C:6]([CH3:8])=[C:5]([C:9]([O:11][CH3:12])=[O:10])[CH:4]([C:13]2[C:18]([N+:19]([O-:21])=[O:20])=[CH:17][CH:16]=[CH:15][CH:14]=2)[C:3]=1[C:22]([O:24][CH3:25])=[O:23]12 g nifedipine was introduced into a 100-mL three-neck flask and dissolved in 50 mL tetrahydrofuran under nitrogen. 1.66 g of a 60% dispersion of sodium hydride in oil was then added with stirring. After stirring for a short period of time, 10 mL methyl iodide was added and the reaction was stirred for 1 hour at 38° C. 200 mL ethyl acetate was then added, and the organic layer was thereafter washed several times with water and dried over sodium sulfate. The sodium sulfate was subsequently filtered off and the solvent was then pulled off from the filtrate on a rotary evaporator. The obtained solid was dissolved in 200 mL MIBK, and the addition of hexane to this solution then yielded 8.9 g N-methylnifedipine as yellow crystals. mp=184°-187° C.
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