Synthesis of Coumarin Conjugates of Biological Thiols for Fluorescent Detection and Estimation

Coumarin-labeled thioesters are efficiently prepared from biological thiols using N-coumarin-3-carbonyl benzotriazoles. Absorption (lambda(abs)), fluorescence (lambda(em)) wavelength maxima and quantum yields (phi) for the thioesters are measured in buffer solution at physiological pH 7.4. Quantum yields (phi = 0.0318-0.1068) of four of the products are higher than their precursor 7-methoxy-3-(1H-benzotriazol-1-ylcarbonyl)-2H-chromen-2-one (phi = 0.0195), suggesting that derivatives of this type could be suitable for quantitative thiol assays.