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. Author manuscript; available in PMC: 2014 Oct 27.
Published in final edited form as: J Am Chem Soc. 2013 Mar 11;135(11):4333–4363. doi: 10.1021/ja3109664

Scheme 3.

Scheme 3

Proline editing alternative approach: synthesis of the peptide Ac-TYP(4R-O-Alloc)N-NH2(15) via Alloc protection and direct acylation. The Alloc group was stable to TFA cleavage/deprotection. a

a (a) 20% piperidine/DMF; (b) Fmoc-Asn(Trt)-OH, HBTU, DIPEA/DMF; (c) Fmoc-Tyr(OtBu)-OH, HBTU, DIPEA/DMF; (d) Fmoc-Thr(OtBu)-OH, HBTU, DIPEA/DMF; (e) 10% Ac2O/pyridine. RN′ = Ac-Thr(OtBu)-Tyr(OtBu)-, RC′ = -Asn(Trt)-NHRink-Resin. RN = Ac-Thr-Tyr-, RC = -Asn-NH2

b Reaction was performed in a glass vial manually.