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. Author manuscript; available in PMC: 2013 Jan 1.
Published in final edited form as: Bioorg Med Chem Lett. 2011 Nov 15;22(1):377–379. doi: 10.1016/j.bmcl.2011.10.122

Scheme 3.

Scheme 3

Reagents and reaction conditions: i) 1-Boc-piperazine/NaHB(OAc)3/CH2Cl2; ii) TFA/CH2Cl2; iii) EDCl/R4COOH/DMF or R4CHO/NaHB(OAc)3/CH2Cl2 or R4SO2Cl/TEA/CH2Cl2.