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. Author manuscript; available in PMC: 2015 Jun 16.
Published in final edited form as: Chembiochem. 2014 May 18;15(9):1263–1267. doi: 10.1002/cbic.201402135

Scheme 2. Synthesis and application of the ligation auxiliary.

Scheme 2

A) i) BrCH2CH2Br, Et3N, DMF, 18 h, 25 °C, 64%; ii) TrtSH, NaH, DMF, 2 h, 25 °C, 79%; iii) H 2NNH2, CHCl3, 2.5 h, 25 °C, 90%. B) i) 1. 1% TFA, 1% TIS in CH2Cl2; 2. BrCH2COOH, DIC, DMF; ii) 1, 1 M in DMSO; iii) Reagent K; iv) Ub(1-75)-α-thioester (3), 6 M Gn-HCl, 100 mM Na2HPO4, 10 mM TCEP, pH 7.5; v) 6 M Gn-HCl, Zn, pH 3.0, 37 °C, 24 h. PG = protecting group, Trt = trityl, Mtt = 4-methyltrityl, Ac = acetyl, Boc = tert-butyloxycarbonyl, Fmoc = 9-Fluorenylmethoxycarbonyl, TFA = trifluoroacetic acid, TIS = triisopropylsilane, DIC = N,N′-Diisopropylcarbodiimide, Reagent K = 82.5:5:5:5:2.5, TFA: thioanisole: H2O: phenol: 1,2-ethanedithiol (v/v), Gn-HCl = guanidinium hydrochloride, TCEP = Tris(2-carboxyethyl)phosphine.