摘要：

Examination of nature's favorite mol- ecules reveals a striking preference for making carbon -heteroatom bonds over carbon -carbon bonds-surely no surprise given that carbon dioxide is nature's starting material and that most reactions are performed in water . Nucleic acids, proteins, and polysac- charides are condensation polymers of small subunits stitched together by carbon- heteroatom bonds. Even the 35 or so building blocks from which these crucial molecules are made each contain, at most, six contiguous C-C bonds, except for the three aromatic amino acids. Taking our cue from nature's approach, we address here the development of a set of powerful, highly reliable, and selective reactions for the rapid synthesis of useful new compounds and combinatorial libra- ries through heteroatom links (C-X-C), an approach we call "click chemistry". Click chemistry is at once defined, enabled, and constrained by a handful of nearly perfect "spring-load- ed" reactions. The stringent criteria for a process to earn click chemistry status are described along with examples of the molecular frameworks that are easily made using this spartan, but powerful, synthetic strategy.

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