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. Author manuscript; available in PMC: 2019 Dec 15.
Published in final edited form as: Bioorg Med Chem Lett. 2018 Oct 25;28(23-24):3648–3651. doi: 10.1016/j.bmcl.2018.10.039

Scheme 4.

Scheme 4.

Reagents and conditions: (a) triphosgene, toluene/EtOAc, 0-80 °C, 12 h; (b) tert-butyl 2-amino-2-methylpropanoate hydrochloride, DIPEA, CH2Cl2, 0 °C to rt, 12 h; (c) CuI, DBU, DMSO, 120 °C, 0.3 h; (d) TFA, CH2Cl2, rt, 24 h.