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. 2019 Mar 22;15:761–768. doi: 10.3762/bjoc.15.72

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Copyright © 2019, Ng-Choi et al.

This is an Open Access article under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0). Please note that the reuse, redistribution and reproduction in particular requires that the authors and source are credited.

The license is subject to the Beilstein Journal of Organic Chemistry terms and conditions: (https://www.beilstein-journals.org/bjoc/terms)

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Scheme 3 — Synthesis of the biaryl bicyclic peptide 2 incorporating a Phe-Tyr linkage. Reagents and conditions: (i) Piperidine/DMF (3:7). (ii) Fmoc-βAla-OH, DIPCDI, Oxyma, DMF. (iii) Fmoc-Phe(4-I)-OH, COMU, Oxyma, DIPEA, DMF, overnight. (iv) Fmoc-Gln(Tmob)-OH, DIPCDI, Oxyma, DMF. (v) Fmoc-Gly-OH, DIPCDI, Oxyma, DMF. (vi) Fmoc-Ala-OH, DIPCDI, Oxyma, DMF. (vii) Boc-Tyr(3-B(OH)₂,Me)-OH, DIPCDI, Oxyma, DMF, 3 h. (viii) Pd₂(dba)₃, SPhos, KF, DME/EtOH/H₂O (9:9:2), MW, 120 °C, 30 min. (ix) TFA/H₂O/TIS (95:2.5:2.5), 2 h. (x) TMSOTf, 2,6-lutidine, CH₂Cl₂. (xi) PyOxim, Oxyma, DIPEA, NMP, 24 h.