Photocages are light-sensitive chemical protecting groups that provide external control over when, where, and how much of a biological substrate is activated in cells using targeted light irradiation. Regrettably, most popular photocages (e.g., o-nitrobenzyl groups) absorb cell-damaging ultraviolet wavelengths. A challenge with achieving longer wavelength bond-breaking photochemistry is that long-wavelength-absorbing chromophores have shorter excited-state lifetimes and diminished excited-state energies. However, here we report the synthesis of a family of BODIPY-derived photocages with tunable absorptions across the visible/near-infrared that release chemical cargo under irradiation. Derivatives with appended styryl groups feature absorptions above 700 nm, yielding photocages cleaved with the highest known wavelengths of light via a direct single-photon-release mechanism. Photorelease with red light is demonstrated in living HeLa cells, Drosophila S2 cells, and bovine GM07373 cells upon ∼5 min irradiation. No cytotoxicity is observed at 20 μM photocage concentration using the trypan blue exclusion assay. Improved B-alkylated derivatives feature improved quantum efficiencies of photorelease ∼20-fold larger, on par with the popular o-nitrobenzyl photocages (εΦ = 50-100 M cm), but absorbing red/near-IR light in the biological window instead of UV light.

Photoremovable protecting groups derived from meso-substituted BODIPY dyes release acetic acid with green wavelengths >500 nm. Photorelease is demonstrated in cultured S2 cells. The photocaging structures were identified by our previously proposed strategy of computationally searching for carbocations with low-energy diradical states as a possible indicator of a nearby productive conical intersection. The superior optical properties of these photocages make them promising alternatives to the popular o-nitrobenzyl photocage systems.

This report describes the direct conversion of aldehydes and ketones into alkyl azides by the addition of common organometallic reagents and tandem conversion of the resulting alkoxides without isolation of the intermediate alcohols. A wide range of aldehydes and organometallic reagents (R–Li or R–MgX) are suitable participants in this process. Additional reaction telescoping beyond azide formation is demonstrated.

We report that aryl phthalate esters are robust self-immolative linkers. This linker is easy to conjugate and releases output phenols upon cleaving a fluoride-sensitive mask to yield a benign phthalic acid byproduct, making these linkers potentially useful as fluoride sensors and promising for use in biological and materials applications. ABSTRACT: We report that aryl phthalate esters are robust selfimmolative linkers. This linker is easy to conjugate and releases output phenols upon cleaving a fluoride-sensitive mask to yield a benign phthalic acid byproduct, making these linkers potentially useful as fluoride sensors and promising for use in biological and materials applications. Disciplines

Self-immolative aryl phthalate esters were conjugated with cleavable masking groups sensitive to light and hydrogen peroxide. The phthalate linker releases the fluorescent dye 7-hydroxycoumarin upon exposure to light or H2O2, respectively, leading to an increase in fluorescence. The light-sensitive aryl phthalate ester is demonstrated as a pro-fluorophore in cultured S2 cells.

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