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. Author manuscript; available in PMC: 2019 Apr 10.
Published in final edited form as: ACS Chem Biol. 2018 Aug 16;13(9):2542–2550. doi: 10.1021/acschembio.8b00477

Scheme 2.

Synthesis of analogs 1-5 from common intermediate 10

Scheme 2.

aReagents and conditions: (a) Fmoc-Lys(Boc)-OH or Fmoc-Glu(OtBu)-OH, HBTU, DIPEA, DMF; (b) 20% piperidine in DMF; (c) 2-Azido-acetic acid or α-azido-Lys(Boc)-OH, HBTU, DIPEA, DMF; (d) THPTA, CuSO4, sodium ascorbate, alkyne-R; (e) 95/2.5/2.5 TFA:TIS:H2O; (f) diethyl squarate, Et3N, DMF; (g) R-NH2, Et3N, CH2Cl2.