Peptide Modification via N-Terminal-Residue-Directed γ-C(sp3)-H Arylation.

Postassembly modification of peptides via C(sp3)-H functionalization provides an efficient way to prepare functionalized peptides for biological study and pharmaceutical development. In this work, we developed a new method for γ-C(sp3)-H functionalization of aliphatic side chains of N-terminus-unprotected peptides. With the N-terminal residues as directing groups, a wide range of di-, tri-, tetra-, and pentapeptides underwent C-H arylation of the residues (Val, Ile, Tle) at the +2 position from the N-terminus.

Site-Selective Modification of α-Amino Acids and Oligopeptides via Native Amine-Directed γ-C(sp3)-H Arylation.

Site-selective modification of chemically and biologically valuable α-amino acids and peptides is of great importance for biochemical study and pharmaceutical development. Few methods based on remote C(sp3)-H functionalization of aliphatic side-chains of peptides has been disclosed in recent years. In this report, we developed a novel approach for γ-C(sp3)-H and γ-/δ-C(sp2)-H arylation of α-amino acids with α-hydrogen by native amine-directed C-H functionalization and further realized the γ-C(sp3)-H arylation of N-terminally unprotected peptides.

Free Amino Group-Directed γ-C(sp3)-H Arylation of α-Amino Esters with Diaryliodonium Triflates by Palladium Catalysis.

Free amino group-directed C(sp3)-H functionalization of aliphatic amines is a fundamental challenge in synthetic organic chemistry. Also, the NH2-directed C(sp3)-H functionalization of α-amino acids and their derivatives remains barely explored. With palladium as the catalyst and Ag2O as the additive, we developed the first NH2-directed γ-C(sp3)-H arylation of α-amino esters with diaryliodonium triflates for the construction of synthetically useful γ-aryl-α-amino esters, and the result of the KIE study suggested that the catalytic reaction involved an irreversible C-H cleavage as the rate-determining step.