title: Photochemical transformation of 5-alkyluracils and their nucleosides.
abstract: 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.
mesh_terms: D000478:Alkylation; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D066298:In Vitro Techniques; D008027:Light; D009682:Magnetic Resonance Spectroscopy; D008967:Molecular Biology; D009705:Nucleosides / Q000138:chemical synthesis*; D010777:Photochemistry; D011743:Pyrimidines / Q000138:chemical synthesis*; D011830:Radiation Effects; D014498:Uracil / Q000138:chemical synthesis*; D014529:Uridine / Q000528:radiation effects
chemical_list: D009705:Nucleosides; D011743:Pyrimidines; D014498:Uracil; D014529:Uridine