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Degradation of Benzylpenicillin at pH 7.5 to D-Benzylpenicilloic Acid



IN acid aqueous solution, benzylpenicillin (I) becomes rearranged to D-benzylpenicillic acid1a, and in alkaline aqueous solution, it is hydrolysed to the α-diastereomer of D-benzylpenicilloic acid1b (II). The product of degradation of benzylpenicillin in aqueous solution at pH 7.5 has not been identified. During work on the mechanism of antigenicity of penicillin, it was necessary to investigate the degradation pathway of benzylpenicillin under physiological conditions. It was found that in aqueous solution at pH 7.5, benzylpenicillin is degraded to D-benzylpenicilloic acid, which appeared to be present as a mixture of its diastereomers.

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  1. 1

    Cited by: Florey, H. W., Chain, E., Heatley, N. G., Jennings, M. A., Sanders, A. G., Abraham, E. P., and Florey, M. E., “Antibiotics”, 2 (Oxf. Univ. Press, London, 1949). (a) p. 889 ; (b) p. 840 ; (c) p. 803 ; (d) p. 839 ; (e) see p. 844 for a discussion of the stereochemistry of penicilloic acids.

  2. 2

    Cited in : “Chemistry of Penicillin”, edit. by Clarke H. T., Johnson J. R., and Robinson, R. (Princeton Univ. Press, Princeton, N.J., 1949): (a) pp. 162, 431 ; (b) p. 426 ; (c) p. 477 ; (d) p. 482 ; (e) p. 573.

  3. 3

    Shriner, R. L., and Fuson, R. C., “The Systematic Identification of Organic Compounds”, 171 (John Wiley and Sons, Inc., New York, 1948).

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