Fig. 3
From: Synthesis of disulfide-rich heterodimeric peptides through an auxiliary N, N-crosslink
Synthesis of human insulin. Synthesis of human insulin from the N–N chemical ligation of purified A- and B-chains, followed by intramolecular disulfide bond formation, and sebsequently, linker cleavage by DKP formation. (□-isoacyl dipeptide is indicated by a blue box). a 20 equiv. BrCH2COOH, 10 equiv. DIC, 1 h. b Isobutyl amine, 6 equiv. in DMSO, overnight. c Boc-Lys(Fmoc)-OH, DEPBT, DIEA, and DMAP (5%), 4 h. d Fmoc-N-amido-PEG8-acid, DIC, and 6-Cl-HOBt, 4 h. e Bis-boc-amino-oxyacetic acid, DIC, and 6-Cl-HOBt, 1 h. f TFA, TIS, DODT, and H2O, 2 h. g Terephthalaldehyde 10 equiv., 70% aqueous ACN. h Ligation in 0.1% TFA containing 50% aqueous ACN, 2 h. i Folding, Cys-Cystine, pH 9, 4 °C, 12 h. j 0.5 M sodium phosphate buffer at 56 °C
