反应详情

To a solution of the above starting material (3a) in dichloromethane (13 parts) under nitrogen are added at -5° to 0° C. pyridine (2 equivalents) and at -30° to -25° C. phosphorus pentachloride (1.7 equivalents). The mixture is stirred at -15° to -10° C. for 4 hours, cooled to -25° to -30° C., mixed with isobutanol (10 parts) cooled at -30° to -20° C., and let stand at 0° to 5° C. overnight. The reaction mixture is cooled to -20° to -25° C., mixed dropwise with triethylamine (10.9 equivalents), and kept at 0° to 5° C. overnight. The reaction mixture is diluted with dichloromethane (20 parts) and ice water (20 parts) and stirred for 20 minutes. 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: 60.8%.

1. customat -30° to -25° C.
2. temperaturecooled to -25° to -30° C.
3. temperaturecooled at -30° to -20° C.
4. waitlet stand at 0° to 5° C. overnight
5. temperatureThe reaction mixture is cooled to -20° to -25° C.
6. waitkept at 0° to 5° C. overnight
7. stirringstirred for 20 minutes
8. washwashed with hydrochloric acid, water, aqueous sodium hydrogen carbonate, and water
9. customdried
10. concentrationconcentrated
11. customThe residue is crystallized from ethyl acetate