Efficient Automated Solid‐Phase Synthesis of DNA and RNA 5′‐Triphosphates

A fast, high‐yielding and reliable method for the synthesis of DNA‐ and RNA 5′‐triphosphates is reported. After synthesizing DNA or RNA oligonucleotides by automated oligonucleotide synthesis, 5‐chloro‐saligenyl‐N,N‐diisopropylphosphoramidite was coupled to the 5′‐end. Oxidation of the formed 5′‐phosphite using the same oxidizing reagent used in standard oligonucleotide synthesis led to 5′‐cycloSal‐oligonucleotides. Reaction of the support‐bonded 5′‐cycloSal‐oligonucleotide with pyrophosphate yielded the corresponding 5′‐triphosphates. The 5′‐triphosphorylated DNA and RNA oligonucleotides were obtained after cleavage from the support in high purity and excellent yields. The whole reaction sequence was adapted to be used on a standard oligonucleotide synthesizer.