Coumarin-Caged Glycine that Can Be Photolyzed within 3 μs by Visible Light†

The synthesis and characterization of a new photolabile precursor of glycine (coumarin-caged glycine) are reported. The new compound is suitable for rapid chemical kinetic investigations of the membrane-bound neurotransmitter receptor activated by glycine. Unlike previously used caging groups for glycine, this precursor can be photolyzed rapidly and efficiently in the visible wavelength region. This allows the use of a relatively inexpensive light source. The α-carboxyl group of glycine was covalently coupled to the 7-(diethylamino)coumarin (DECM) caging group. The caged compound has a major absorption band with a maximum at 390 nm (e390 = 13 900 M-1 cm-1). Photolysis was performed at wavelengths of ≥400 nm (e400 = 12 400 M-1 cm-1). Under physiological conditions, DECM-caged glycine is water soluble and stable. In the visible wavelength region, it photolyzes rapidly to release glycine with a half-life of ∼2.5 μs and a quantum yield of 0.12 ± 0.01. The experimental results demonstrated that neither DECM-ca...