Photochemical Transformation of 5-Alkyluracils and Their Nucleosides

Science  30 Jul 1971:
Vol. 173, Issue 3995, pp. 435-437
DOI: 10.1126/science.173.3995.435


Irradiation at 254 nm of aqueous solutions of 5-ethyl-, 5-propyl-, and 5-isopropyluracils (or their nulcleosides) leads to cleavage of the 5-alkyl substituents, via an intramolecular electrocyclic photoaddition intermediate, with formation of uracil (or its nucleoside). The plhotoaddition intermediates represent a new class of dihydropyrimidines, namely analogs of 5,6-dihydro-5,6-cyclobutanyluracil and its nucleosides; the biological significance is discussed.