Photocycloaddition of deoxyuridines to 2,3-dimethyl-2-butene

Article abstract of DOI:10.1246/bcsj.67.728

Direct and ketone (acetone or acetophenone)-sensitized photocycloaddition of 2,3-dimethyl-2-butene fo 2'-deoxyuridine (1a), thymidine (1b), 5-fluoro-2'-deoxyuridine (1c), and their 3',5'-di- O-acetyl derivatives 1d-1f by near-UV irradiation have been studied. The triplet excited state of the nucleosides was found to be the major intermediate by the triplet quenching technique. From the respective reactants, a pair of diastereomeric products having a cyclobutane ring were isolated. The absolute configuration of the bridgehead carbon atoms was identified by X-ray crystallographic analyses with two of them as (1R, 6R)-isomer 3a and (1S, 6S)-isomer 2b and by ¹H NMH. The conformations of the glycosyl bond, the pyrimidine ring, and the sugar portion in solution were identified by ¹H NMR and compared with the ones in the crystalline state.