p-Hydroxyphenacyl, a new photoactive, aqueous soluble protecting group is proposed as a second generation α-keto “cage” reagent, a phototrigger for the efficient, rapid release of bioactive phosphates, eg, inorganic phosphate (Pi) and ATP (Givens, RS; Park, C.-H. Tetrahedron Lett. 1996, 37, 6259-6262). p-Hydroxyphenacyl esters 6c and 7 trigger the release of Pi and ATP when irradiated at wavelengths between 300-350 nm also yielding ...