Making functional connections: A summary of the Nobel Prize in Chemistry 2022

Abstract

<p indent="0mm">The Nobel Prize in Chemistry 2022 was awarded to three scientists for their work in the development of click chemistry and bioorthogonal chemistry: Carolyn R. Bertozzi from Stanford University, Morten Meldal from the University of Copenhagen, and K. Barry Sharpless from Scripps Research. Notably, this is the second time Sharpless was awarded this prize. In 2001, he received his first Nobel Prize for the development of catalytic asymmetric oxidation reactions. This year’s prize, however, is in a completely different area, as will be summarized below. For both click chemistry and bioothogonal chemistry, their focus is on making easy connections between molecules and snapping them together. Although modern chemistry has experienced substantial development since its birth in the eighteenth century, dealing with complex molecules and systems remains a challenging and laborious process that requires skill and knowledge. Synthesis has become the bottleneck for the discovery of molecular functions. In 2001, Sharpless and co-workers coined the concept of click chemistry, by defining a set of stringent criteria so that few good reactions could be sorted out for making easy and modular connections: Molecules could be linked together simply like buckling up through a “click”. Later in 2002, Sharpless group published the first click-type reaction, namely the copper-catalyzed azide-alkyne cycloaddition (CuAAC). The reaction is silent without catalyst due to the high kinetic barrier, but become as fast as a “click” to generate triazoles in the presence of copper(I) with a strong thermodynamic driving force. Independently, Meldal made a similar discovery during the peptide synthesis. Over the years, CuAAC has proved itself to be a reliable tool for connecting chemical units of various forms together, nearly under any circumstances with high fidelity. In the late 1990s, in Bertozzi’s search for chemical tools for sugar labeling on the surface of living cell, she realized that the key for successful utilization of a chemical handle was the non-interfering nature of the involved reactions with the surrounding biological environments. She termed this kind of non-interfering reactivity as bioothogonal chemistry. By metabolically incorporating unnatural sialic acids to the cell surface, including the azide derivatives, Bertozzi successfully used Staudinger reaction to attach imaging probes on the cell with amide connections. The iconic breakthrough took place in 2004 when click chemistry was merged with bioothogonal chemistry for the first time. Bertozzi developed a stain-promoted azide-alkyne cycloaddition (SPAAC), which gave improved connection capability for biorthogonal cell imaging without the need of a catalyst, nor any compromise on bioorthogonality. The impact of click chemistry and bioorthogonal chemistry is tremendous and ever-growing. They have inspired the innovation of many connection tools, such as the inverse electron-demand Diels-Alder reaction, photoclick chemistry, and the sulfur(VI)-fluoride exchange (SuFEx) reaction. Apart from serving as tools for tracking and manipulating biomolecules and related events <italic>in vivo</italic>, they have also been used for material sciences and medicinal chemistry. For instance, sacituzumab govitecan is a Trop-2-directed antibody and topoisomerase inhibitor drug conjugate approved by the FDA for the treatment of metastatic triple-negative breast cancer and metastatic urothelial cancer. The key linkage is a CuAAC-derived 1,2,3-triazole. In short, there remain a lot of challenges in chemistry and the related fields to be addressed through diverse strategies and chemical approaches nowadays. The mission of chemistry is to bring the greatest benefit to mankind through continuous innovation and integration.