Fig. 2: Synthesis and screening of NAT bioorthogonal fluorogenic luminophores.
From: Nitrile-aminothiol bioorthogonal near-infrared fluorogenic probes for ultrasensitive in vivo imaging
a Chemical structures and sensing mechanisms of nitrile-substituted hemicyanines with free cysteine via NAT click reaction. b Synthetic routes for CyN-1−5. Reagents and conditions: (i) 2-bromocyclohex-1-ene-1-carbaldehyde, Cs2CO3, DMF, rt, 12 h. (ii) 1,2,3,3-tetramethyl-3H-indolium iodide, AcONa, Ac2O, 60 °C, 2−4 h. (iii) vilsmeier haack reagent, EtOH, reflux, 4 h. (iv) 5-formyl-2,4-dihydroxybenzonitrile, K2CO3, DMF, 50 °C, 12 h. (v) Cs2CO3, CH3I, ACN, rt, overnight. c The second order rate constant (M−1 s−1) and fluorescence enhancement of CyN-1−5 in the presence of free cysteine. d Fluorescence spectra of CyN-1−5 (20 μM) in the absence or presence of Cysteine (100 μM) in PBS (containing 20% MeOH, pH = 7.4) at room temperature. The fluorescence excitation was set at 580 nm. The experiments in d were repeated independently three times with similar results. Source data are provided as a Source Data file.
