Photo-reduction of Pteridines


THE recent communication by Prof. A. Albert1 on the photo-reduction of pteridines prompts me to record another example. In the preparation of 2-amino-4-hydroxy-pteridine-6-aldehyde by the method of Waller et al. 2 it was found that if the initial decomposition of pteroyl-L-glutamic acid to dihydro-2-amino-4-hydroxy-pteridine-6-aldehyde was done in the dark only a poor yield was obtained (as judged by the amount of 2-amino-4-hydroxy-pteridine-6-aldehyde formed on subsequent oxidation). If the reacting solution was irradiated with light from a 100-W. bulb then a good yield was obtained. It thus seems that the decomposition of pteroyl-L-glutamic acid to the dihydro aldehyde is a light-catalysed intramolecular hydrogen transfer from the 9 : 10 position followed by hydrolysis of the resulting anil. It has been previously reported that pteroyl-L-glutamic acid is decomposed by ultra-violet light to 2-amino-4-hydroxy-pteridine-6-aldehyde3. The position of the hydrogen atoms of the dihydro 2-amino-4-hydroxy-pteridine-6-aldehyde in the pyrazine ring has not been established; but this aldehyde would seem to be a possible intermediate in the biological synthesis of the yellow fluorescent eye pigment4 of Drosophila and possibly also of the red pteridine pigments4. Tho primary step in the degradation of pteroyl-L-glutamic acid would seem to be hydrogen transfer intramolecularly to the pyrazine ring or intermolecularly to a suitable hydrogen acceptor (for example, oxygen5 or methylene blue6).


  1. 1

    Albert, A., Nature, 178, 1072 (1956).

  2. 2

    Waller, C. W., Goldman, A. A., Angier, R. B., Boothe, J. H., Hutchings, B. L., Mowat, J. H., and Semb, J., J. Amer. chem. Soc., 72, 4630 (1950).

  3. 3

    Lowry, O., Bessel, O., and Crawford, E., J. Biol. Chem., 180, 389 (1949).

  4. 4

    Forrest, H. S., and Mitchell, H. K., J. Amer. Chem. Soc., 76, 5656 (1954).

  5. 5

    Mowat, J. H., Boothe, J. H., Hutchings, B. L., Stokstad, E. L. R., Waller, C. W., Angier, R. B., Semb, J., Cosulich, D. B., and Subbarow, J., J. Amer. Chem. Soc., 70, 14 (1948).

  6. 6

    Blair, J. A., Biochem. J., 65, 209 (19576).

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BLAIR, J. Photo-reduction of Pteridines. Nature 179, 489–490 (1957).

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