tert-Butyl bromoacetate → Diphenylmethyl 7-[2-(2-tritylamino-4-thiazolyl)-2-(tert.-butoxycarbonylmethyloxyimino)-acetamido]-3-acetoxymethyl-ceph-3-eme-4-carboxylate

Participants

Reaction Steps

A mixture of 0.85 g of the product of Step D, 0.8 ml of tert.-butyl bromoacetate and 4 ml of dimethylformamide stood in an ice bath for 5 minutes and then 1.7 g of silver oxide were added thereto. The mixture was stirred for one hour after removal of the bath and the mixture was vacuum filtered. The filter was rinsed with ethyl acetate and 80 ml of water were added to the filtrate which was decanted. The aqueous phase was extracted twice with 20 ml of ethyl acetate and the combined organic phases were washed twice with 50 ml of aqueous sodium chloride solution, dried, treated with 80 mg of activated carbon and vacuum filtered. The filter was rinsed with ethyl acetate and the filtrate was evaporated to dryness under reduced pressure. The residue was taken up in isopropyl ether and after efflorescence, the mixture was vacuum filtered. The product was rinsed with isopropyl ether and dried to obtain 0.724 g of the syn isomer of diphenylmethyl 7-[2-(2-tritylamino-4-thiazolyl)-2-(tert.-butoxycarbonylmethyloxyimino)-acetamido]-3-acetoxymethyl-ceph-3-eme-4-carboxylate with Rf=0.34 (methylene chloride containing 5% of ether).

Provenance & Evidence