Radical-Mediated Activation of Esters with a Copper/Selectfluor System: Synthesis of Bulky Amides and Peptides

Chemoselective Cleavage and Transamidation of Tertiary p-Methoxybenzyl Amides under Metal-Free Photoredox Catalysis

A metal-free and mild cleavage of tertiary p-methoxybenzyl amides (PMB tert-amide) under photoredox conditions is developed using Mes-Acr-Ph+BF4- and Selectfluor to activate the electron-rich benzylic C-H bond of the PMB moiety. The resulting acyl fluoride intermediate is versatile and facilitates a one-pot transamidation of the PMB tert-amide. The value of this protocol is highlighted by performing the chemoselective activation of the PMB tert-amide in bifunctional molecules containing more reactive functionalities than the amide.

Chemoselective Approach to Versatile Acyl Fluorides by Photoinduced Activation of p-Methoxybenzyl Esters

A new strategy for the metal-free photoinduced activation of p-methoxybenzyl esters is developed using Selectfluor and benzil for the generation of acyl fluoride intermediates that enable various transformations. The highlight of this activation method is its high chemoselectivity in the presence of other functionalities, such as esters, amides, and ketones. A synthetic application for the preparation of peptide mimetics that possess two different amide units is also described.

Organocatalytic Activation of Inert Hydrosilane for Peptide Bond Formation

We describe the development of a reliable catalytic protocol for peptide bond formation that is generally applicable to natural and unnatural α-amino acids, β-amino acids, and peptides bearing various functional groups. A 10 mol % loading of HSi[OCH(CF₃)₂]₃ as a catalyst was sufficient to guarantee a consistently high yield of the resulting peptide. This method facilitates the sustainable utilization of natural resources by using a catalyst and an auxiliary based on earth-abundant silicon.

Ni-catalysed deamidative fluorination of amides with electrophilic fluorinating reagents

We describe here a Ni-catalysed deamidative fluorination of diverse amides with electrophilic fluorinating reagents. Different types of amides including aromatic amides and olefinic amides were well compatible, affording the corresponding acyl fluorides in good to excellent yields.

NDTP Mediated Direct Rapid Amide and Peptide Synthesis without Epimerization

Herein, we explored an unprecedented mild, nonirritating, conveniently available, and recyclable coupling reagent NDTP, which could activate the carboxylic acids via acyl thiocyanide and enable the rapid amide and peptide synthesis at very mild conditions. In addition, the methodology was compatible with Fmoc-SPPS, which may provide an alternative to peptide manufacturing.

Carboxylic Acid Deoxyfluorination and One-Pot Amide Bond Formation Using Pentafluoropyridine (PFP)

This work describes the application of pentafluoropyridine (PFP), a cheap commercially available reagent, in the deoxyfluorination of carboxylic acids to acyl fluorides. The acyl fluorides can be formed from a range of acids under mild conditions. We also demonstrate that PFP can be utilized in a one-pot amide bond formation via in situ generation of acyl fluorides. This one-pot deoxyfluorination amide bond-forming reaction gives ready access to amides in yields of ≤94%.