The copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction between azides and alkynes to form 1,2,3-triazoles is so exquisitely regioselective and efficient at even the most mild conditions that the term 'Click Chemistry' was coined to describe it. The use of copper(I)-stabilizing ligands has led to the use of click chemistry to functionalize alkyne-modified DNA nucleobases with extremely high efficiency. Alternatively, copper free click reactions are possible using highly strained alkyne groups. At Glen Research, our goal was to offer a copper-free click phosphoramidite reagent with the following properties: ? Simple to use ? Stable in solution on the synthesizer ? Stable to ammonium hydroxide and AMA ? Excellent click performance in 17 hours or less at room temperature From the variety of cyclooctyne-based copper-free click reagents so far described, we have chosen to offer compounds based on a dibenzo-cyclooctyne (DBCO) structure.