Phosphorous Compounds for the Synthesis of Triphosphonates of Oligonucleotides

5-Chlorosaligenyl-N,N-diisopropylphosphoramidite (1) and bis(tetrabutylammonium) dihydrogen pyrophosphate (2) are useful reagents to introduce a triphosphate group onto the 5'-end of oligonucleotides. Oligonucleotides can react with 1 in the presence of BTT and subsequent oxidation with iodine to give the 5’-cyclophosphate ester 3. Furthermore, 3 can attach the corresponding triphosphate upon the reaction with 2. 1 and 2 are applicable to both solid phase synthesis and a standard oligonucleotide synthesizer, and are anticipated to be powerful tools in chemical and biochemical research.