Helix-Constrained Peptides Constructed by Head-to-Side Chain Cross-Linking Strategies

Chemical Synthesis of Proteins Using an o-Nitrobenzyl Group as a Robust Temporary Protective Group for N-Terminal Cysteine Protection

We report here a robust and practical strategy for chemical protein synthesis using an o-nitrobenzyl group as a temporary protective group for an N-terminal cysteine residue of intermediate hydrazide fragments. By reinvestigating the photoremoval of an o-nitrobenzyl group, we establish a robust and reliable strategy for its quantitative photodeprotection. The o-nitrobenzyl group is completely stable to oxidative NaNO₂ treatment and has been applied to the convergent chemical synthesis of programmed death ligand 1 fragment, providing a practical avenue for hydrazide-based native chemical ligation.

Head-to-Tail Cross-Linking to Generate Bicyclic Helical Peptides with Enhanced Helicity and Proteolytic Stability

We report a new pattern of a bicyclic helical peptide constructed through head-to-tail cross-linking. The described bicyclic helical peptide has a head-to-tail cross-linking arm and a C-terminal i, i + 4 cross-linking arm. This scaffold will provide a promising scaffold for designing a proteolytically resistant helix-constrained peptide.