A practical approach for oligopeptide synthesis via synergistic photoredox, cobaloxime and organophosphorus triple catalysis

Abstract

A catalytic oxidation–reduction condensation strategy for the synthesis of oligopeptides is reported. The triple catalytic system is compatible with all proteinogenic amino acids and applicable for multigram scale peptide synthesis.

Photocatalytic Phosphine-Mediated Thioesterification of Carboxylic Acids with Disulfides

“…High-resolution mass spectrometry (HRMS) analysis detected two distinct TEMPO adducts, indicating the generation of acyl radical D and thiyl radical E . On the basis of our experimental observations as well as previous studies, a mechanism for the thioesterification reaction is proposed in Scheme . Under visible light irradiation, the reaction proceeds with the single-electron oxidation of Ph 2 POEt [ E 1/2 [ B / A ] = +1.17 V versus saturated calomel electrode (SCE)] via a reductive quenching cycle. , Nucleophilic trapping of phosphine radical cation B by the carboxylate anion results in the formation of phosphoranyl radical C .…”

“…In their work, the nickel catalyst played a pivotal role in facilitating the formation of C–S bonds via reductive elimination. As a part of our continued interest in phosphoranyl radical-mediated transformations, , we herein disclose the successful application of this deoxygenative process for thioester synthesis through direct radical–radical coupling (path b in Scheme C). This photocatalytic strategy reaches the goal of radical thioesterification from readily available carboxylic acids and allows for incorporation of both S atoms from odorless disulfides into the desired product.…”

Visible-light-induced Fe(iii)-promoted reduction amidation of 1,4,2-dioxazol-5-one

“…9–12 Historically, the preparation of amides has encompassed a broad range of methods, including the employment of carbon diimide condensation reagents, 13–15 onium salt condensation reagents, 16–18 and organophosphorus condensation reagents. 19–21…”