Scheme 1. Design and Synthesis of the Clickable and Photoreactive Bile Acid Probes.

Reagents and conditions: (a) L1, BOP, DIPEA, DMF, 24 h, 85%. (b) Ag₂CO₃ on Celite (50 wt %), toluene, 140 °C, 36 h, 92%. (c) (1) NH₃, MeOH, 0 °C, 3 h; (2) HOSA, −15 °C, 2 h, then rt, 14 h; (3) I₂, TEA, MeOH, 30 min, 76%. (d) NaOH, MeOH, 36 h, quant. (e) 2-Propynylamine, HBTU, DIPEA, DMF, 20 h, 95%. (f) L2, BOP, DIPEA, DMF, 24 h, 88%.