Metal-free reductive desulfurization of C-sp³-substituted thiols using phosphite catalysis

Abstract

Phosphines and phosphites are critical tools for non-metal desulfurative methodologies due to the strength of the P=S bond. An overarching premise in these methods has been that stoichiometric (or excess)...

Peptide macrocyclisation via intramolecular interception of visible-light-mediated desulfurisation

“…Several methods for the desulfurisation of Cys residues have been reported in the literature, these include; photo-induced desulfurisation 69 using a ruthenium PC, 60 photo-desulfurisation in flow, 61 accelerated desulfurisation using tetraethylborate (NaBEt 4 ), 63 desulfurative borylation, 64 and the exploitation of phosphite 66 and phosphine-dependent pathways. 65 We attempted to adapt and explore two appropriate examples.…”

“…54,55 Desulfurisation of Cys (and alternative non-proteinogenic thiol-containing amino acids [56][57][58] ) can be applied post-peptide ligation as an elegant method to access a broad range of ligation junctions and facilitate chemical protein synthesis. 56,[59][60][61][62][63][64][65][66][67] A widely used free-radicalmediated Cys desulfurative protocol, 59 developed by Danishefsky and co-workers, proceeds via a thiophosphoranyl radical species generated using a radical initiator (VA-044) to form a thiyl radical from the thiol sidechain of Cys in the presence of the water-soluble phosphine, tris(2-carboxyethyl)phosphine hydrochloride (TCEP). b-Scission of the thiophosphoranyl radical 62 produces a peptide 'alanyl' radical which, in the presence of a suitable thiol additive (e.g.…”

Photoredox catalyzed hydroazolylation of alkenes via phosphoranyl radicals

“…Therefore, this activation strategy has witnessed a wide range of recent applications in deoxygenation, decarboxylation and desulfurization reactions of diverse common organic functional groups. 8…”