Abstract— Photochemical and γ‐ray‐induced reactions of purines with amines are described. These lead to the appropriate 8‐substituted purines. The photoproducts were obtained in yields of up to 100% by the use of a variety of photosensitizers, including peroxides. A free radical mechanism is proposed for these reactions. Such reactions may be relevant to the problem of the nature of DNA‐protein cross‐links induced by ultraviolet radiation.

Abstract— Ultraviolet light irradiation of DNA in the presence of alcohols such as 2‐propanol leads to hydroxyalkylation of the purine bases. The purine photoproducts were identified as C‐8 hydroxyalkyl derivatives of adenine and guanine by chromatographic mobility, co‐crystallization with authentic samples, and by photoreversal to the original purines. Experiments are reported which demonstrate that the photoalkylation reaction is dependent upon secondary structural alterations in DNA. It is suggested that the photoalkylation of purines proceeds through free‐radical intermediates. The presence of alcohols during irradiation considerably decreases pyrimidine‐dimer formation.

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Suwzmnry C-8-H ydroxyalkylpurines and purine nucleosides upon irradiation are transformed into the original purines.