Patent ID: 8318953

Claim:
A coumarin compound of the formula: wherein ECG is an acetyl, acetoxymethyl, acetoxyalkylmethyl, acetoxyarylmethyl or a low acyl of 3-10 carbon atoms; L is a linker; RG is a chemically reactive group; R 1 , R 2 , R 3 and R 4 are independently H, halogen, alkyl, alkoxy, aryloxy, thiol, alkylthiol, arylthiol, azido, amino, hydroxyl or boronic acid, RG or L-RG provided that R 3 and R 4 are not simultaneously H or F; and, wherein the —(C═O)-L-RG moiety is a succinimidyl ester, nitrophenol ester, polychlorophenol ester, or polyfluorophenol ester.