Photocleavable Protecting Groups Using a Sulfite Self-Immolative Linker for High Uncaging Quantum Yield and Aqueous...

Using light as an external stimulus to control (bio)chemical processes offers many distinct advantages. Most importantly, it allows for spatiotemporal control simply through operating the light source. Photocleavable protecting groups (PPGs) are a cornerstone class of compounds that are used to achieve photocontrol over (bio)chemical processes. PPGs are able to release a payload of interest upon light irradiation. The successful application of PPGs hinges on their efficiency of payload release, captured in the uncaging Quantum Yield (QY). Heterolytic PPGs efficiently release low pK_a payloads, but their efficiency drops significantly for payloads with higher pK_a values, such as alcohols. For this reason, alcohols are usually attached to PPGs via a carbonate linker. The self-immolative nature of the carbonate linker results in concurrent release of CO₂ with the alcohol payload upon irradiation. We introduce herein novel PPGs containing sulfites as self-immolative linkers for photocaged alcohol payloads, for which we discovered that the release of the alcohol proceeds with higher uncaging QY than an identical payload released from a carbonate-linked PPG. Furthermore, we demonstrate that uncaging of the sulfite-linked PPGs results in the release of SO₂ and show that the sulfite linker improves water solubility as compared to the carbonate-based systems.