title: The Dewar valence isomer of the (6-4) photoadduct of thymidylyl-(3'-5')-thymidine monophosphate: formation, alkaline lability and conformational properties.
abstract: The formation of the Dewar valence isomer of the pyrimidine(6-4)pyrimidone photoadduct of thymidylyl-(3'-5')-thymidine monophosphate (TpT) was investigated under different irradiation conditions. This photoproduct was generated on exposure of TpT to far-UV radiation. However, no detectable amount of the Dewar isomer or its precursor (pyrimidine(6-4)pyrimidone photoadduct) was observed following acetone photosensitization of TpT. The Dewar valence isomer was much more unstable than the pyrimidine(6-4)pyrimidone photoproduct when treated with hot piperidine. A detailed conformational analysis of the TpT Dewar isomer photoproduct is reported as inferred from extensive one- and two-dimensional 300 and 620 MHz proton nuclear magnetic resonance (1H NMR) measurements and molecular mechanics calculations.
authors.affiliation: Department of Biochemistry, Johns Hopkins University, Baltimore, MD 21205.
authors.forename: L S
authors.initials: LS
authors.lastname: Kan
authors.forename: L
authors.initials: L
authors.lastname: Voituriez
authors.forename: J
authors.initials: J
authors.lastname: Cadet
mesh_terms: D015226:Dinucleoside Phosphates / Q000737:chemistry / Q000528:radiation effects*; D004355:Drug Stability; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D010782:Photolysis; D016339:Spectrometry, Mass, Fast Atom Bombardment; D014466:Ultraviolet Rays
chemical_list: D015226:Dinucleoside Phosphates; C017758:thymidylyl-(3'-5')-thymidine