A 2-hydroxyphenacyl moiety absorbing below 370 nm is proposed as a new photoremovable protecting group for carboxylates and sulfonates. Laser flash photolysis and steady-state sensitization studies show that the leaving group is released from a short-lived triplet state. In addition, DFT-based quantum chemical calculations were performed to determine the key reaction steps. We found that triplet excited state intramolecular proton transfer represents a major deactivation channel. Minor productive pathways involving the triplet anion and quinoid triplet enol intermediates have also been identified.

Department of Chemistry Faculty of Science Masaryk University Kamenice 5 625 00 Brno Czech Republic

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Photoremovable protecting groups in chemistry and biology: reaction mechanisms and efficacy