Herein is reported an operationally simple method to facilitate chemical protein synthesis by fully convergent and one-pot native chemical ligations utilizing the fluorenylmethyloxycarbonyl (Fmoc) moiety as an N-masking group of the N-terminal cysteine of the middle peptide thioester segment(s).

The Fmoc group is stable to the harsh oxidative conditions frequently used to generate peptide thioesters from peptide hydrazide or o-aminoanilide. The ready availability of Fmoc-Cys(Trt)-OH, which is routinely used in Fmoc solid-phase peptide synthesis, where the Fmoc group is pre-installed on cysteine residue, minimizes additional steps required for the temporary protection of the N-terminal cysteinyl peptides. The Fmoc group is readily removed after ligation by short exposure (<7 min) to 20% piperidine at pH 11 in aqueous conditions at room temperature. Subsequent native chemical ligation reactions can be performed in presence of piperidine in the same solution at pH 7.

Title:
Efficient Chemical Protein Synthesis using Fmoc-Masked N-Terminal Cysteine in Peptide Thioester Segments
Authors:
Abhisek Kar, Jamsad Mannuthodikayil, Sameer Singh, Anamika Biswas, Puneet Dubey, Amit Das, and Kalyaneswar Mandal
Citation:
Angew. Chem. Int. Ed. 2020, 59, 2–8
URL:
https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202000491