O=[C:2]1[CH2:5][N:4]([C:6]([O:8][CH2:9][CH3:10])=[O:7])[CH2:3]1.Cl.Cl.[NH2:13][C:14]1[CH:22]=[CH:21][CH:20]=[C:19]([F:23])[C:15]=1[C:16]([NH2:18])=[NH:17].C(=O)(O)[O-].[Na+]>CN(C=O)C>[NH2:18][C:16]1[C:15]2[C:14](=[CH:22][CH:21]=[CH:20][C:19]=2[F:23])[NH:13][C:2]2([CH2:5][N:4]([C:6]([O:8][CH2:9][CH3:10])=[O:7])[CH2:3]2)[N:17]=1Ethyl 3-oxoazetidine-1-carboxylate (Y. Nitta, T. Yamagouchi, T. Tanaka; Heterocycles, 1986, 24, 25) (175 mg, 1.22 mmol) and 2-amino-6-fluorobenzamidine dihydrochloride (Example C, 280 mg, 1.22 mmol) in dry DMF (10 ml) were heated at 80° C. for 4 hours. The resulting solution was cooled and poured into aqueous sodium bicarbonate solution and the resulting mixture was extracted with ethyl acetate. The extracts were concentrated and the residue purified by flash chromatography on silica eluting with dichloromethane/methanol (10:1) to give the title compound as a solid (0.13 g) m.p. 210°-212° C.
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