Trifluoroacetic acid → 7beta-Phenoxyacetamido-3-hydroxy-3-cephem-4-carboxylic acid p-nitrobenzyl ester

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Reaction Steps

A solution of 340 mg of the resulting isomer mixture, consisting of 7β-phenoxyacetamido-3-diphenylmethoxy-ceph-2-em-4α-carboxylic acid p-nitrobenzyl ester and 7β-phenoxyacetamido-3-diphenylmethoxy-ceph-3-em-4-carboxylic acid p-nitrobenzyl ester, in a mixture of 0.5 m. of trifluoroacetic acid and 9.5 ml of methylene chloride is stirred for 40 minutes at room temperature. The mixture is concentrated by evaporation in vacuo, toluene is added to the residue, and the mixture is again concentrated by evaporation. The resulting residue (which still contains trifluoroacetic acid) is chromatographed on 15 g of acid-washed silica gel, using toluene/ethyl acetate (3:1), whereby 7β-phenoxyacetamido-3-hydroxy-ceph-3-em-4-carboxylic acid p-nitrobenzyl ester is obtained; 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 8.3 μ; NMR spectrum (deuterochloroform): characteristic bands at 3.4 (2H, AB q, ] = 17 Hz), 4.57 (2H, s), 5.06 (1H, d,] = 5 Hz), 5.35 (2Y, AB q, ] = 14 Hz), 5.7 (1H, dd,] = 5, 10 Hz), 6.8-8.4 (10 H, c), 11.4 (1H, br. s.) ppm.

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