Brominated hydroxyquinoline as a photolabile protecting group with sensitivity to multiphoton excitation
The synthesis and photochem. of a new photolabile protecting group for carboxylic acids based on 8-bromo-7-hydroxyquinoline (BHQ) is described. BHQ possesses a greater single photon quantum efficiency than 4,5-dimethoxy-4-nitrobenzyl ester (DMNB) and 6-bromo-7-hydroxycoumarin-4-ylmethyl (Bhc), and it has sufficient sensitivity to multiphoton-induced photolysis for use in vivo. Its increased soly. and low fluorescence make it quite useful as a caging group for biol. messengers.