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. We are offering 5"-DBCO-TEG Phosphoramidite for preparing oligos with a 5"-DBCO modification and DBCO-dT-CE Phosphoramidite for inserting a DBCO group at any position within the oligonucleotide. DBCO-sulfo-NHS Ester is also offered for post-synthesis conjugation reactions. DBCO-modified oligos may be conjugated with azides in organic solvents, such as DMSO, or aqeous buffers. Depending on the azide used, the reaction will go to completion in 4-17 hours at room temperature. Simple desalting on a Glen Gel-Pak™ leads to a product with virtually quantitative conjugation efficiency.

Note: We now recommend that synthesis of oligos containing DBCO-dT be completed using 0.5 M CSO in anhydrous acetonitrile (40-4632-xx). Acceptable results can be achieved with iodine oxidation if DBCO-dT is subjected to no more than 8-10 cycles.