3-Azidocoumarin is an organic compound that is used in the area of bioconjugation. It is a derivative of coumarin, a natural product and precursor for the widely used Coumadin. Azidocoumarin has emerged as a widely applicable labeling agent in diverse biological systems. In particular, it participates in the aptly named click reaction with alkynes.[1] Bioconjugation involves the labeling of certain cellular components and is applicable to fields such a proteomics and functional genomics with a detachable, fluorescent tag.[2]
A common way to produce the 3-azidocoumarin is by condensation of salicylaldehyde and N-acetylglycine or nitroacetate.[3] The intermediate is trapped with sodium azide to produce the 3-azidocoumarin. The isomeric 4-azidocoumarin (CAS# 42373-56-8) product can also be prepared from 4-hydroxycoumarin via the 4-chloro derivative, which reacts with sodium azide.[4]
This compound is used for bioconjugation. The target, which contains a terminal alkyne functional group, is treated with the organic azide in the presence of a Cu(I) catalyst. The resulting 1,2,3-triazole is fluorescent. The coumarin backbone is chosen to be used as the profluorophore due to its small size, biocompatibility, and its ability to be easily manipulated synthetically.[3] Illustrative of this is the labeling of biological compounds such as the protein calmodulin.[5] Neither the azidocoumarin nor the alkyne substrate fluoresce. Azidocoumarin is also inert in biological systems and insensitive to pH and solvent. A variety of azidocoumarin compounds have been evaluated.