Efficient Activation of 6-Nitropiperonyloxymethylene (NPOM)-Caged Nucleosides with Visible Light

摘要

Caging groups are photoremovable protecting groups that render a molecule biologically inactive until light illumination, thereby allowing for temporal and spatial control of activity. While nitrobenzyl-based caging groups have advantageous synthetic and photochemical properties, red shifting of the absorption spectrum through chemical modification has led to reduced decaging efficiency. 6-Nitropiperonyloxymethylene (NPOM), a group with broad applicability in the caging of heterocyclic structures, in particular nucleic acids, traditionally requires ultraviolet (UV) irradiation for decaging. Herein, we investigated the decaging properties of NPOM under near visible light (400-450 nm) using N~3-caged 5'-dimethoxytrityl (DMTr)-thymidine as a substrate. To our surprise, we discovered highly efficient decaging at wavelengths outside the UV range, in particular when compared to other nitrobenzyl chromo-phores. These results have implications in the selection of light sources for photoactivation and for sequential photolysis to achieve selective control of biological processes.