反应详情

The isomer mixture obtained, consisting of 7β-phenoxyacetamido-3-benzoxy-ceph-2-em-4α-carboxylic acid p-nitrobenzyl ester and 7β-phenoxyacetamido-3-benzoxy-ceph-3-em-4-carboxylic acid p-nitrobenzyl ester in the ratio of about 3:1, is dissolved in 8 ml of trifluoroacetic acid and the solution is stirred for 90 minutes at room temperature. The reaction mixture is then concentrated by evaporation in vacuo and residual trifluoroacetic acid is repeatedly driven off with toluene. The residue is chromatographed on 20 g of acid-washed silica gel, using toluene/ethyl acetate (3:1), giving 7β-phenoxyacetamido-3-hydroxy-ceph-3-em-4-carboxylic acid p-nitrobenzyl ester in the form of a colourless foam. 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): characteristic bands at 3.4 (2H, AB q, J=17 Hz), 4.57 (2H, s), 5.06 (1H, d, J=5 Hz), 5.35 (2H, AB q, J=14 Hz), 5.7 (1H, dd, J=5, 10 Hz), 6.8-8.4 (10H, c), 11.4 (1H, br.s.) ppm.

1. customThe isomer mixture obtained
2. concentrationThe reaction mixture is then concentrated by evaporation in vacuo and residual trifluoroacetic acid
3. customThe residue is chromatographed on 20 g of acid-washed silica gel