Tetrazole Diversification of Amino Acids and Peptides via Silver-Catalyzed Intermolecular Cycloaddition with Aryldiazonium Salts

Selective structural modification of amino acids and peptides is a central strategy in organic chemistry, chemical biology but also in pharmacology and material science. In this context, the formation of tetrazole rings, known to possess significant therapeutic properties, would expand the chemical space of unnatural amino acids but has received less attention. In this study, we demonstrated that the classic unimolecular Wolff rearrangement of α-amino acid-derived diazoketones could be replaced by a faster intermolecular cycloaddition reaction with aryldiazonium salts under identical practical conditions. This strategy provides an efficient synthetic platform that could transform proteinogenic α-amino acids into a plethora of unprecedented tetrazole-decorated amino acid derivatives with preservation of the stereocenters. Density functional theory studies shed some light on the reaction mechanism and provided information regarding the origins of the chemo- and regioselectivity. Furthermore, this diazo-cycloaddition protocol was applied to construct tetrazole-modified peptidomimetics and drug-like amino acid derivatives.

Natural and synthetic cytokinins and their applications in biotechnology, agrochemistry and medicine

The review is devoted to cytokinins — classical plant hormones known for more than six decades. Nevertheless, different aspects of the action of cytokinins are still being investigated. Relevant studies produced interesting, often unexpected, results, which cast doubt on the old paradigms and open new prospects for the use of these phytohormones. Particular attention is given to recent advances in the applications of natural cytokinins and their synthetic analogues in biotechnology, agriculture, medicine and cosmetics. The chemical synthesis, properties and the possible use of artificial cytokinins are considered in detail. The review is aimed at researchers interested in the development and applications of new biologically active compounds with a wide spectrum of action on diverse biological objects, from plants to humans.

The bibliography includes 233 references.