Scheme 1. Solid-phase synthesis of fluorescent probes 3 and 4. Boc = tert-butoxycarbonyl, DEPBT = 3-(diethoxyphosphoryloxy)-1,2,3-benzotriazin-4(3H)-one, HATU = O-(7-aza-1H-benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate, HOAt = 1-hydroxy-7-azabenzotriazole, MW = microwave, PyBOP = (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate, t-Bu = tert-butyl, TFA = trifluoroacetic acid.
