Coumarin-Based Octopamine Phototriggers and their Effects on an Insect Octopamine Receptor

We have developed and characterized efficient caged compounds of the neurotransmitter octopamine. For derivatization, we introduced [6-bromo-8-(diethylaminomethyl)-7-hydroxycoumarin-4-yl]methoxycarbonyl (DBHCMOC) and {6-bromo-7-hydroxy-8-[(piperazin-1-yl)methyl]coumarin-4-yl}methoxycarbonyl (PBHCMOC) moieties as novel photo-removable protecting groups. The caged compounds were functionally inactive when applied to heterologously expressed octopamine receptors (AmOcta1R). Upon irradiation with UVvisible or IR light, bioactive octopamine was released and evoked Ca2+ signals in AmOcta1R-expressing cells. The pronounced water solubility of compounds 24 in particular holds great promise for these substances as excellent phototriggers of this important neurotransmitter.