Amine Activation:N-Arylamino Acid Amide Synthesis from Isothioureas and Amino Acids

Visible-Light-Driven Method for the Selective Synthesis of Amides and N-Acylureas from Carboxylic Acids and Thioureas

In this work, we developed a visible-light-driven method for the selective synthesis of amides and N-acylureas from carboxylic acids and thioureas. This protocol was featured as avoidance of additional oxidants and transition metal catalysts, simple manipulations, low cost, broad substrate scope, and good functional group tolerance. As only oxygen serves as the oxidation reagent, this method provides a promising synthesis candidate for the formation of N-aryl amides and N-acylureas, including late-stage functionalization of complex pharmaceutical molecules and biologically active molecules.

Amine Activation: "Inverse" Dipeptide Synthesis and Amide Function Formation through Activated Amino Compounds

A copper(II)/HOBt-catalyzed procedure for the synthesis of dipeptides and "general" amides has been developed using microwave irradiation to considerably hasten the reaction. As an alternative to using traditional carboxylic acid activation, the method relies on the use of N-acyl imidazoles as activated amino partners. By doing so, a nonconventional way to reach dipeptides and amides has been proposed through the challenging and less studied N → C direction synthesis. A series of dipeptides and "general" amides have been successfully synthesized, and the applicability of the method has been illustrated in gram-scale syntheses. The mild reaction conditions proposed are completely adequate for couplings in the presence of sensitive amino acids, affording the products without detectable racemization. Furthermore, experimental observations prompted us to propose a plausible reaction pathway for the couplings.

Umpolung strategies for the functionalization of peptides and proteins

Umpolung strategies, defined as synthetic approaches which reverse commonly accepted reactivity patterns, are broadly recognized as enabling tools for small molecule synthesis and catalysis. However, methods which exploit this logic for peptide and protein functionalizations are comparatively rare, with the overwhelming majority of existing bioconjugation approaches relying on the well-established reactivity profiles of a handful of amino acids. This perspective serves to highlight a small but growing body of recent work that masterfully capitalizes on the concept of polarity reversal for the selective modification of proteinogenic functionalities. Current applications of umpolung chemistry in organic synthesis and chemical biology as well as the vast potential for further innovations in peptide and protein modification will be discussed.

Design, Synthesis, and Bioactivity of α-Ketoamide Derivatives Bearing a Vanillin Skeleton for Crop Diseases

A series of novel α-ketoamide derivatives bearing a vanillin skeleton were designed and synthesized. Bioactivity tests on virus and bacteria were performed. The results indicated that some compounds exhibited excellent antitobacco mosaic virus (TMV) activities, such as compound 34 exhibited an inactivation activity of 90.1% and curative activity of 51.8% and compound 28 exhibited a curative activity of 54.8% at 500 μg mL^-1, which is equivalent to that of the commercial ningnanmycin (inactivation of 91.9% and curative of 51.9%). Moreover, the in vitro antibacterial activity test illustrated that compounds 2, 22, and 33 showed much higher activities than commercial thiodiazole copper, which could be used as lead compounds or potential candidates. The findings of transmission electron microscopy and molecular docking indicated that the synthesized compounds exhibited strong and significant binding affinity to the TMV coat protein and could obstruct the self-assembly and increment of TMV particles. This study revealed that α-ketoamide derivatives bearing a vanillin skeleton could be used as a novel potential pesticide for controlling the plant diseases.

Clickable coupling of carboxylic acids and amines at room temperature mediated by SO2F2: a significant breakthrough for the construction of amides and peptide linkages

The construction of amide bonds and peptide linkages is one of the most fundamental transformations in all life processes and organic synthesis. The synthesis of structurally ubiquitous amide motifs is essential in the assembly of numerous important molecules such as peptides, proteins, alkaloids, pharmaceutical agents, polymers, ligands and agrochemicals. A method of SO2F2-mediated direct clickable coupling of carboxylic acids with amines was developed for the synthesis of a broad scope of amides in a simple, mild, highly efficient, robust and practical manner (>110 examples, >90% yields in most cases). The direct click reactions of acids and amines on a gram scale are also demonstrated using an extremely easy work-up and purification process of washing with 1 M aqueous HCl to provide the desired amides in greater than 99% purity and excellent yields.

Beckmann Rearrangement of Ketoxime Catalyzed by N-methyl-imidazolium Hydrosulfate

Beckmann rearrangement of ketoxime catalyzed by acidic ionic liquid-N-methyl-imidazolium hydrosulfate was studied. Rearrangement of benzophenone oxime gave the desirable product with 45% yield at 90 °C. When co-catalyst P₂O₅ was added, the yield could be improved to 91%. The catalyst could be reused three cycles with the same efficiency. Finally, reactions of other ketoximes were also investigated.