Copper‐Catalyzed Huisgen 1,3‐Dipolar Cycloaddition Tailored for Phosphorothioate Oligonucleotides

AbstractAn efficient method for attachment of a variety of reporter groups to oligonucleotides (ONs) is copper (I) [Cu(I)]‐catalyzed Huisgen azide‐alkyne 1,3‐dipolar cycloaddition (“click reaction”). However, in the case of ONs with phosphorothioate modifications as internucleosidic linkages (PS‐ONs), this conjugation method has to be adjusted to be compatible with the sulfur‐containing groups. The method described here is adapted for PS‐ONs, utilizes solid‐supported ONs, and implements the Cu(I) bromide dimethyl sulfide complex (CuBr × Me2S) as a mediator for the click reaction. The solid‐supported ONs can be readily transformed into “clickable ONs” by on‐line addition of an alkyne‐containing linker that subsequently can react with an azido‐containing moiety (e.g., a peptide) in the presence of CuBr × Me2S. © 2019 by John Wiley & Sons, Inc.Basic Protocol 1: Conjugation on solid supportSupport Protocol: Removal of 4,4′‐dimethoxytrityl group from amino linkerBasic Protocol 2: Removal of protecting groups and cleavage from solid supportBasic Protocol 3: HPLC purification