Diketene → Benzhydryl 7-(4-bromoacetoacetamido)-3-methylthiomethyl-3-cephem-4-carboxylate

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Reaction Steps

To a solution of diketene (1.3 ml) in methylene chloride (10 ml) was added dropwise a solution of bromine (1.24 g) in methylene chloride (10 ml) at -30° C. with stirring, and the stirring was continued at -20° C. for half an hour to prepare a solution of 4-bromoacetoacetyl bromide. This solution was added dropwise to a solution of benzhydryl 7-amino-3-methylthiomethyl-3-cephem-4-carboxylate (4.44 g) and trimethylsilylacetamide (5.46 g) in methylene chloride (100 ml) at -30° to -20° C. over a period of 5 minutes with stirring, and the stirring was continued at -10° C. for half an hour. After addition of water, the resultant mixture was adjusted to pH 7.5 with an aqueous solution of sodium bicarbonate, followed by separating out the organic layer, which was washed with water and an aqueous solution of sodium chloride, dried over anhydrous magnesium sulfate, and then evaporated to dryness to give benzhydryl 7-(4-bromoacetoacetamido)-3-methylthiomethyl-3-cephem-4-carboxylate (6.0 g).

Provenance & Evidence