反应详情

A solution of 148 mg (0.2 mmol) of a mixture consisting of 2-[4-(p-toluenesulphonylthio)-3-phenoxyacetamido-2-oxoazetidin-1-yl]-3-(N-methylcyclohexylamino)-crotonic acid p-nitrobenzyl ester and the corresponding isocrotonic acid ester, in 3 ml of dry acetonitrile, is heated under nitrogen for about 4 hours at 80° C until no further starting material can be detected by thin layer chromatography (silica gel: toluene/ethyl acetate, 1:1). The heating bath is removed, 38 mg (0.2 mmol) of p-toluenesulphonic acid and about 0.2 ml of water are added to the reaction mixture and the mixture is stirred for a further 2 hours at room temperature. The reaction mixture is diluted with benzene, washed with water, dried over sodium sulphate and evaporated in vacuo. The residue is triturated at 0° C with diethyl ether and gives pale yellow 7β-phenoxyacetamido-3-hydroxy-3-cephem-4-carboxylic acid p-nitrobenzyl ester. IR spectrum (methylene chloride): characteristic bands at 2.95; 3.3; 5.6; 5.75 (sh); 5.9; 5.95 (sh) 6.55, 7.45, 8.15 and 8.3μ; NMR spectrum (deuterochloroform); δ in ppm: 3.4 (zH, q, J = 17 Hz); 4.57 (2H, s); 5.06 (1H, d; J = 5 Hz); 5.35 (2H, q, J = 14 Hz); 5.7 (1H dd, J = 5, 10 Hz); 6.8-8.4 (10H, c) and 11.4 (1H, br.s.).

1. customThe heating bath is removed
2. washwashed with water
3. dry with materialdried over sodium sulphate
4. customevaporated in vacuo
5. customThe residue is triturated at 0° C with diethyl ether