 left" HSPACE=5> |
The 3'-
N-sulfamate analogue of thymidylyl(3'-5')thymidine (TnsoT,
1) exhibits a preference for a C3'-endo conformation in the solution and solid states. Its photochemical behavior in solution is comparedto that of its natural counterpart, thymidylyl(3'-5')thymidine (TpT,
2), to get further insight into thesignificance of the C3'-endo conformation on the photoproduct formation at the single-stranded dinucleotidelevel. Irradiation at 254 nm of
1 led to the same type of photoproducts as observed with
2. However,
1was significantly more photoreactive than
2, and accordingly, the initial rate of photoproduct formationwas enhanced in accordance with its propensity to base stack compared to
2. The corresponding quantumyields were determined and showed that the enhancement factor (
1 compared to
2) is moderate for thecyclobutane pyrimidine dimer (CPD) (1.26) and much higher for the (6-4) photoproduct (1.8). Thesedata strongly suggest that the CPD and (6-4) photoproduct arise from distinct minor stacked conformations.
