Phosphorus pentachloride → cis-3-{2-(2-Chloroacetamido-4-thiazolyl)-2-[1-methyl-1-(2-trimethylsilylethoxycarbonyl)ethoxyimino]acetamido}-4-methoxycarbonyl-2-oxoazetidine

Participants

Reaction Steps

In 25 ml of methylene chloride is dissolved 820 mg of 2-(2-chloroacetamido-4-thiazolyl)-2-[1-methyl-1-(2-trimethylsilylethoxycarbonyl)ethoxyimino]acetic acid, and under ice-cooling 221 mg of triethylamine and then 380 mg of phosphorus pentachloride are added. The mixture is stirred under ice-cooling for 15 minutes and then at room temperature for 2 hours. The reaction mixture is concentrated under reduced pressure and the residue is dissolved in 5 ml of tetrahydrofuran to prepare a solution containing the acid chloride. On the other hand, 219 mg of cis-3-amino-4-methoxycarbonyl-2-oxoazetidine is dissolved in a mixture of 5 ml of tetrahydrofuran and 10 ml of water, followed by addition of 638 mg of sodium hydrogen carbonate under ice-cooling. To this solution is added dropwise the above acid chloride solution under stirring. The mixture is stirred under ice-cooling for 15 minutes and then at room temperature for one hour and extracted with ethyl acetate. The extract is dried over anhydrous magnesium sulfate and the solvent is distilled off to give cis-3-{2-(2-chloroacetamido-4-thiazolyl)-2-[1-methyl-1-(2-trimethylsilylethoxycarbonyl)ethoxyimino]acetamido}-4- methoxycarbonyl-2-oxoazetidine (syn-isomer).

Provenance & Evidence