aReagents and conditions: (a) 1-Cbz-piperazine, K2CO3, DMF, 90°C, 12 h; (b) Hydrazine monohydrate, EtOH, reflux, overnight; (c) Propionaldehyde, THF/MeOH, rt, 30 min, then NaBH4, MeOH, rt, 2 h; (d) Boc2O, TEA, DCM, rt, overnight; (e) H2, Pd/C (10%), MeOH, 4 h; (f) HATU, DIPEA, DCM, rt, overnight; (g) K2CO3, KI, MeCN, 65°C, overnight; (h) TFA, DCM, rt, 2 h.