Fluorous Phototriggers:  Efficacy, Variability, and Mechanism Dependency with Neurotransmitter Release.  Kenneth F.  Stensrud, and Richard S. Givens.  Department of Chemistry, University of Kansas, 1251 Wescoe Hall Drive, 4049 Malott Hall, Lawrence, KS, 66045-7582, Fax:  785-864-3846, givensr@ku.edu 

Photoremovable protecting groups (ppg) afford both temporal and spatial control over release of substrates.  Photolysis severs a covalent linkage between the chromophore and substrate, thereby reinstating the free, active substrate.  Demonstrated photochemical and photophysical properties of p-hydroxyphenacyl (pHP) include rapid, efficient, and clean photorelease of a variety of bioactive species.  For example, the photolysis of p-hydroxyphenacyl-γ-aminobutyric acid (pHP-GABA) occurs with greater than 20% efficiency for release with a rate constant of 1.82 x 10⁸ s^-1.  Further studies have revealed improvements in these properties when electron withdrawing groups are attached to the pHP-GABA. New fluorinated pHP-γ-aminobutyric acid and l-glutamate derivatives have been synthesized and examined for their efficiencies and rates.  In addition to photochemical studies, novel synthetic routes to these fluorinated, acetophenone-based chromophores will be highlighted.