Toluene → 3-Acetoxy-7beta-phenylacetylaminocepham-4alpha-carboxylic acid diphenylmethyl ester

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A mixture of 0.312 g of 3 -hydroxy-7β-phenylacetylamino-cepham-4α-carboxylic acid diphenylmethyl ester in 15 ml of pyridine and 7 ml of acetic anhydride is left to stand for 16 hours at 0° C and after addition of 50 ml of toluene is evaporated under reduced pressure. The residue is taken up in ethyl acetate; the organic solution is washed with a saturated aqueous sodium bicarbonate solution and a saturated aqueous sodium chloride solution, dried over sodium sulphate and evaporated under reduced pressure. The residue is purified by means of preparative thin layer chromatography; a silica gel plate of 100 cm length is used and development is carried out with a 1:1 mixture of toluene and ethyl acetate. 3 -Acetoxy-7β-phenylacetylaminocepham-4α-carboxylic acid diphenylmethyl ester of Rf = 0.47 is obtained, melting at 162°-164° C after crystallisation from a mixture of methylene chloride and pentane; [α]D20 = + 55° ± 1° (c = 0.492 in chloroform); ultraviolet absorption spectrum (in 95% strength ethanol): λmax = 253 mμ (ε = 700), 258 mμ (ε = 820) and 265 mμ (ε = 660): infrared absorption spectrum (in methylene chloride): characteristic bands at 2.96μ, 5.66μ, 5.77μ, 5.97μ, 6.28μ and 6.71μ.

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