Scheme 1. Synthesis of truncated inhibitor 5. Reagents and conditions: (a) 1-Boc-4-piperidinol, DIAD, PPh₃. THF, rt, 4 h, 94%; (b) NaOH, MeOH/H₂O, 50 °C, 2 h, 90%; (c) (3-methoxyphenyl)methanol, EDCI, HOBt, DIPEA, MeCN, rt, 18 h; (d) 10% TFA in DCM (v/v), rt, 2 h, 9% over 2 steps.