A. L. LEVY1 has described the preparation of anhydro-N-carboxy-DL-β-phenylalanine (II, R=CH2Ph) by the action of phosgene on DL-β-phenylalanine. Prior to this, Fuchs2 described the preparation of anhydro-N-carboxy-N-phenyl- and N-p-tolyl-glycine by phosgenation of the parent acids in aqueous solution. Isatoic anhydride3, the analogous compound from anthranilic acid, has been similarly prepared. A modified method based on this reaction of Fuchs has been used recently by several workers in these laboratories. The process, which is fairly generally applicable and has been protected by a patent application4, consists of suspending the powdered α-amino-acid in a dry inert solvent, for example, dioxan or tetrahydrofuran, at 30°–40° and passing in gaseous phosgene with stirring until the acid is dissolved. Removal of solvent and excess phosgene by heating in vacuo at 40° then affords the anhydro-N-carboxy derivative (II), the intermediate N- substituted carbamyl chloride (I) being decomposed with the loss of hydrochloric acid during the treatment:

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  1. 1

    Levy, A. L., Nature, 165, 152 (1950).

  2. 2

    Fuchs, F., Ber., 55, 2943 (1922).

  3. 3

    Org. Syntheses”, 27, 45 (1947).

  4. 4

    Baird, W., Parry, E. G., Robinson, S., and Imperial Chemical Industries, Ltd., Brit. Pat. Appl. 20406/47 (29.7.47).

  5. 5

    Brown, C. J., Coleman, D., and Farthing, A. C., Nature, 163, 834 (1949).

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FARTHING, A., REYNOLDS, R. Anhydro-N-Carboxy-DL-β-Phenylalanine. Nature 165, 647 (1950) doi:10.1038/165647a0

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