Organic azides, which have recently become important compounds in organic synthesis, have been found to unexpectedly decompose under light.

Organic azides consist of a carbon chain attached to a row of three nitrogen atoms, and have in recent years become valuable compounds in organic chemistry, not least due to their versatility in reactions, such as the 'click' reaction of azides and alkenes. They have also been used as biochemical labels and as drug components.

Now, a team of bioscientists have found that certain organic azides can decompose when exposed to light. Previously, such decomposition was only known to occur under strong heating or intense ultraviolet irradiation. This could raise issues for the future use of these azides in chemical and biochemical applications, say the researchers.

David Fairlie and colleagues at the University of Queensland, Brisbane, Australia, left an azide derivative of an amino acid in a clear glass vial exposed to light, and found that it decomposed at the rate of about one percent a day to give an aldehyde and an amine, which they isolated by chromatography. The aldehyde is known to be much more biologically active than the azide, meaning that even trace amounts could have profound effects, said Fairlie. Summarising, he said that this decomposition has 'very important ramifications for the storage, chemical reactivity, and biological properties of azides'.

Stefan Bräse, professor of organic chemistry at the University of Karlsruhe, Germany, is fascinated by the results. 'Organic azides are always good for surprises,' he said, 'but the discovery that laboratory light might convert azides into bioactive compounds poses both problems and opportunities in the future in biochemistry and chemical biology.'

David Barden