Design and synthesis of new photocaging chromophores and phototchemical carbanion progenitors

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Protecting groups are molecular entities that can be attached to a variety of molecules of interest in order to deactivate a certain feature of that molecule, such as its chemical reactivity or its biological function.  'Photocages' are protecting groups that detach from the molecule of interest when they absorb light (usually in the UVA wavelength range), thereby reactivating the molecule.  Exposure of a 'caged' molecule to brief pulses of light can  cause a sudden increase in the concentration of the molecule of interest in its active form. Photocages are used extensively in this way to suddenly introduce a variety of molecules into biological systems.  Biochemists are then able to study very fast biological events that are triggered by this sudden concentration increase, such as the movements of muscle tissues and communication between nerve cells.  Unfortunately, all currently available photocages suffer from one or more serious drawbacks which limits their utility.  For example, the most popular photocage exhibits poor solubility in water, slow release rate, and leads to formation of interfering by-products.   This research plan is devoted to developing new photocages primarily for use in biological studies and in synthetic applications, that remedy the drawbacks associated with those currently available.  The proposed photocages are of two main types: 1) 'carbocation-mediated' photocages that release the protected molecule by formation of a carbocation reactive intermediate, and 2) 'carbanion-mediated' photocages that release the protected molecules from a first formed carbanion reactive intermediate.  All proposed photocages are expected to show excellent release rates, high efficiency, good aqueous solubility, good absorption in the UVA wavelength range, and formation of benign photoproducts. This research also seeks to broaden the range of light absorbing molecules that can be used to generate carbanion reactive intermediates.  This will enable the creation of new photocages with tunable properties such as reactivity and water solubility.