Pyridine → Benzhydryl 7-amino-3-cephem-4-carboxylate

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Reaction Steps

To a solution of 3-p-toluenesulfonyloxy-7beta-phenylacetylaminocepham-4-carboxylic acid diphenylmethyl ester (3d) in dichloromethane (7 parts) cooling at -15° to -10° C. are added pyridine (2 equivalents) and phosphorus pentachloride (1.7 equivalents). After stirring at -15° to -10° C. for 4 hours, the mixture is diluted with methanol (12 parts) cooled at -40° to -30° C. and then stirred at -30° C. for 30 minutes and at 0° to 5° C. for 2.5 hours. The mixture is cooled to -40° to -30° C., mixed dropwise with triethylamine (8 equivalents), and the mixture is stirred at 0° to 5° C. for 2 hours and let stand overnight. The mixture is diluted with dichloromethane and ice-water and stirred for 20 minutes at 0° to 5° C. The formed organic layer is taken, washed with hydrochloric acid, water, aqueous sodium hydrogen carbonate, and water, dried, and concentrated. The residue is crystallized from ethyl acetate to give 7beta-amino-3-cephem-4-carboxylic acid diphenylmethyl ester (5). Yield: 57.9%.

Provenance & Evidence