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. Author manuscript; available in PMC: 2017 Aug 15.
Published in final edited form as: Bioorg Med Chem. 2016 Jun 11;24(16):3758–3770. doi: 10.1016/j.bmc.2016.06.018

Scheme 1.

Scheme 1

Synthesis of compound 22

Reagents and conditions: a) Diethyl oxalate, MeONa, MeOH, reflux, 6 h, 90%; b) 4-Fluorophenyl hydra-zine hydrochloride, glacial acetic acid, conc. HCl, reflux, 3.5 h, 61%; c) LiOH, MeOH/THF/H2O, rt, 18 h, 87%; d) Tert-butyl (S)-3-amino-5-cyclohexylpentanoate, HBTU, Et3N, CH3CN, rt, 3 h, 79%; e) TFA, DCM, rt, 4 h, 80%