Oxalyl chloride → (6R)-8-Oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid

Beteiligte Stoffe

Reaktionsschritte

2.66 g of 2-(2-tritylaminothiazol-4-yl)-(Z)-2-methoxyiminoacetic acid and 3 ml of dimethylacetamide were dissolved in 50 ml of dichloromethane, and a solution of 0.78 ml of oxalyl chloride in 2 ml of dichloromethane was added gradually thereto at -17° to -15° C. under stirring. After the mixture was stirred at the same temperature for 10 minutes, a solution of 3.22 g of 7β-amino-3-[(1-formamido-1H-tetrazol-5-yl)thiomethyl]-3-cephem-4-carboxylic acid and 3.66 g of triethylamine in dichloromethane (40 ml)-dimethylacetamide (30 ml) was added dropwise thereto at -17° to -13° C. for 15 minutes. Then, the mixture was stirred at -18° for 3 hours. After the reaction, the mixture was evaporated under reduced pressure to remove solvent. Water was added to the residue, and the aqueous solution was washed with ethyl acetate, adjusted to pH 3 with citric acid and then extracted twice with a mixture of 20 ml of ethyl acetate and 5 ml of tetrahydrofuran. The extracts were combined, washed with water, dried and evaporated under reduced pressure to remove solvent. Ether was added to the residue thus obtained, whereby 2.87 g of 7β-[2-(2-tritylaminothiazol-4-yl)-(Z)-2-methoxyiminoacetamido]-3-[(1-formamido-1H)-tetrazol-5-yl)thiomethyl]-3-cephem-4-carboxylic acid were obtained as pale brown powder.

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