Fig. 1. (A) Synthesis route for probe 1. (1) POCl₃, DMF, rt, 34%; (2) dimethyl malonate, piperidine, rt, 84%; (3) THF/10% NaOH = 1 : 1, rt, then 1 M HCl, 70%; (4) NBD-PZ, EDCI, DMAP, rt, 67%; (5) DCM/TFA = 1/1, then Q₃PA, EDCI, DMAP, rt, 44%. (B) Synthesis route for probe 2. (1) N-Boc-ethylenediamine, reflux, 65%; (2) piperazine, reflux, 63%; (3) NBD-Cl, TEA, rt, 66%; (4) DCM/TFA = 1/1, then Q₃PA, EDCI, DMAP, rt, 88%.