[CH3:1][N:2]([CH2:4][C:5]1[O:9][C:8]([CH2:10][S:11][CH2:12][CH2:13][NH2:14])=[CH:7][CH:6]=1)[CH3:3].[CH3:15][NH:16][C:17](SC)=[CH:18][N+:19]([O-:21])=[O:20].Cl>O>[CH3:15][NH:16]/[C:17](/[NH:14][CH2:13][CH2:12][S:11][CH2:10][C:8]1[O:9][C:5]([CH2:4][N:2]([CH3:1])[CH3:3])=[CH:6][CH:7]=1)=[CH:18]\[N+:19]([O-:21])=[O:20]2-[[[5-(Dimethylamino)methyl-2-furanyl]methyl]thio]ethanamine (50 g) and N-methyl-1-(methylthio)-2-nitroetheneamine (40 g) in water (235 ml) was stirred and heated at 45°-50° C. The solution was stirred further for 3-4 hrs. It was acidified with hydrochloric acid and extracted with chloroform. The solution was basified with potassium carbonate and ranitidine base was separated. The water, if any, was removed by azeotropic distillation under reduced pressure at 40°-45° C. using isopropanol. The resultant solution was cooled to 10° C. and n-hexane (500 ml) was added. Ranitidine base was filtered off and dried under vacuum to give the crude product (66.2 g), m.p. 68°-70° C.; purity=99.4% (HPLC); IR(KBr): 3280, 3200, 2820, 2774, 1620, 1580, 1440, 1370, 1258, 1130, 1020, 990, 820, 790, 760, 680 and 600 cm-1 ; δH (CDCl3):2.23 [6H,s, --N(CH3)2 ], 2.75(2H, t, --SCH2CH2), 2.85(3H,br d, CH3NH--), 3.3 (2H,2t, --CH2NH--), 3.4(2H,s, >NCH2), 3.7 (2H,s, CH2 bridge linking), 6.0-6.2 (2H,AB,furan) and 6.5 (,1H,s,=CHNO2).
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