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7902161 
Journal Article 
Intramolecular sensitization of photocleavage of the photolabile 2-(2-nitrophenyl)propoxycarbonyl (NPPOC) protecting group: photoproducts and photokinetics of the release of nucleosides 
Wöll, D; Smirnova, J; Galetskaya, M; Prykota, T; Bühler, J; Stengele, KP; Pfleiderer, W; Steiner, UE 
2008 
Yes 
Chemistry: A European Journal
ISSN: 0947-6539
EISSN: 1521-3765 
14 
21 
6490-6497 
English 
18537211 
WOS:000258092400023 
Novel photolabile protecting groups based on the 2-(2-nitrophenyl)propoxycarbonyl (NPPOC) group with a covalently linked thioxanthone as an intramolecular triplet sensitizer exhibit significantly enhanced light sensitivity under continuous illumination. Herein we present a detailed study of the photokinetics and photoproducts of nucleosides caged with these new protecting groups. Relative to the parent NPPOC group, the light sensitivity of the new photolabile protecting groups is enhanced by up to a factor of 21 at 366 nm and is still quite high at 405 nm, the wavelength at which the sensitivity of the parent compound is practically zero. A new pathway for deprotection of the NPPOC group proceeding through a nitroso benzylalcohol intermediate has been discovered to complement the main mechanism, which involves beta elimination. Under standard conditions of lithographic DNA-chip synthesis, some of the new compounds, while maintaining the same chip quality, react ten times faster than the unmodified NPPOC-protected nucleosides. 
DNA chips; Energy transfer; Photochemistry; Protecting groups; Sensitization