Coupling reactions of hindered isonitriles and hindered alkyl thioacids: Mechanistic studies

Direct Synthesis of α-Ketothioamide Derivatives through a One-Pot Reaction of Sulfur Ylides, Nitrosobenzenes, and Thioacetic Acid

A one-pot approach has been developed for the synthesis of α-ketothioamide derivatives from sulfur ylides, nitrosobenzenes, and thioacetic acid. This protocol is carried out under mild reaction conditions in generally moderate to excellent yields without any precious catalysts, affording the derivatives with structural diversity. Additionally, a possible mechanism for this chemical transformation is proposed.

Thioacids – synthons for amide bond formation and ligation reactions: assembly of peptides and peptidomimetics

The synthesis of α-amino thioacids and peptide thioacids and their applications in chemoselective amide bond formation, ligation of peptides/proteins/glycopeptides and synthesis of peptidomimetics are reviewed.

In situ generation of nitrilium from nitrile ylide and the subsequent Mumm rearrangement: copper-catalyzed synthesis of unsymmetrical diacylglycine esters

A novel in situ generation of nitrilium from nitrile ylide and the subsequent Mumm rearrangement of carboxylic acid, nitrile, and diazo compounds gave various unsymmetrical diacylglycine esters.

Application of Thio-Ugi Adducts for the Preparation of Benzo[b]thiophene and S-Heterocycle Library via Copper Catalyzed Intramolecular C-S Bond Formation

Fused heterocycles, such as benzo[b]thiophene, thiochroman, benzo[b][1,4]thiazine, and 1,4-benzothiazepine were generated from thio-Ugi adducts containing a thioamide group through copper-catalyzed intramolecular C-S bond formation under microwave irradiation.

Solid-phase peptide synthesis and solid-phase fragment coupling mediated by isonitriles

The synthesis of polypeptides on solid phase via mediation by isonitriles is described. The acyl donor is a thioacid, which presumably reacts with the isonitrile to generate a thio-formimidate carboxylate mixed anhydride intermediate. Applications of this chemistry to reiterative solid-phase peptide synthesis as well as solid-phase fragment coupling are described.

A fascinating journey into history: exploration of the world of isonitriles en route to complex amides

We describe herein our recent explorations in the field of isonitrile chemistry. An array of broadly useful coupling methodologies has been developed for the formation of peptidyl and glycopeptidyl amide bonds. We further describe the application of these methods to the syntheses of complex systems, including the cyclic peptide cyclosporine A, constrained peptide systems, and heterocycles.

Expanding the limits of isonitrile-mediated amidations: on the remarkable stereosubtleties of macrolactam formation from synthetic seco-cyclosporins

The scope of isonitrile-mediated amide bond-forming reactions is further explored in this second-generation synthetic approach to cyclosporine (cyclosporin A). Both type I and type II amidations are utilized in this effort, allowing access to epimeric cyclosporins A and H from a single precursor by variation of the coupling reagents. This work lends deeper insight into the relative acylating ability of the formimidate carboxylate mixed anhydride (FCMA) intermediate, while shedding light on the far-reaching impact of remote stereochemical changes on the effective preorganization of seco-cyclosporins.

On the synthesis of conformationally modified peptides through isonitrile chemistry: implications for dealing with polypeptide aggregation

A method for introducing a dimethyleneoxy constraint joining the N atoms of two consecutive amino acids in the context of a polypeptide has been developed. This constraint can profoundly affect the tendency of a polypeptide to suffer aggregation and desolubilization, and it can be readily removed under mild conditions.

Dihydro-3-(triphenylphosphoranylidene)-2,5-thiophendione: A Convenient Synthon for the Preparation of Substituted 1,4-Thiazepin-5-ones and Piperidinones via the Intermediacy of Thioacids

Reaction of thiomaleic anhydride with triphenylphosphine gives the title compound which undergoes reaction with a variety of aldehydes to give a range of alkylidene thiomaleic anhydrides (substituted monothio itaconic anhydrides). Subsequent treatment with tert-butoxycarbonylamino-substituted thiols, or under radical conditions with tert-butoxycarbonylamino-substituted alkyl halides results in a series of substituted monothiomaleic anhydrides, that on exposure to trifluoroacetic acid and then base lead to thiocarboxyl substituted 1,4-thiazepin-5-ones and piperidinones, respectively, that are ultimately trapped by reaction with 2,4-dinitrobenzenesulfonamides to give the corresponding amides.

Thio FCMA intermediates as strong acyl donors: a general solution to the formation of complex amide bonds

Novel methodology for the formation of amide bonds under neutral conditions is described. Evidence is presented that the active acyl donors are thio FCMA intermediates, generated from the reactions of thioacids with isonitriles.

A Simple Method for the Conversion of Carboxylic Acids into Thioacids with Lawesson's Reagent

A one-step protocol for the conversion of carboxylic acids to thioesters, using Lawesson's Reagent, has been developed.