Studies related to penicillins and cephalosporins. Part IV. Synthesis of methyl 7-phthalimido-6,7-trans-DL-cepham-4-carboxylate

Abstract

β-Lactams having a common nitrogen atom with methionine methyl ester were prepared. 1-(1-Methoxycarbonyl-3-methylthiopropyl)-3-phthalimido-4-triphenylmethylthioazetidin-2-one (16) was obtained by the reaction of triphenylmethyl N-(1-methoxycarbonyl-3-methylthiopropyl)thioformimidate (11) with phthaloylglycyl chloride and triethylamine. Detritylation of (16) afforded the corresponding mercapto-β-lactam (15). Treatment of (16) with methyl iodide and sodium iodide in dimethylformamide gave 1-(3-iodo-1-methoxycarbonylpropyl)-3-phthalimido-4-triphenylmethylthioazetidin-2-one (18). This compound was converted into a mercuriothio-derivative (19) which gave methyl 7-phthalimido-6,7-trans-DL-cepham-4-carboxylate (20) by an intramolecular alkylation on the sulphur atom.