Abstract
| - The synthesis and conformational analysis of 2‘-O,5-dimethyluridylyl(3‘-5‘)-2‘-O,5-dimethyluridine(1a), the analogue of thymidylyl(3‘-5‘)thymidine (TpT; 1b) in which a methoxy group replaces each2‘-α-hydrogen atom, are described. In comparison with TpT, such modification increases thepopulation of the C3‘-endo conformer of the sugar ring puckering at the 5‘- and 3‘-ends from 30 to75% and from 37 to 66%, respectively. Photolyses of 1a and TpT at 254 nm are qualitativelycomparable (the cis-syn cyclobutane pyrimidine dimer and the (6-4) photoproduct are formed),although it is significantly faster in the case of 1a. These results are explained by the increasedpropensity of the modified dinucleotide to adopt a base-stacked conformation geometry reminiscentof that for TpT.
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