Synthesis of capped oligoribonucleotides by use of protected 7-methylguanosine 5′-diphosphate derivatives

Abstract

This paper describes the capping reaction of 5′-phosphorylated oligoribonucleotides protected only by a tetrahydropyranyl group at each 2′-position. By use of the conventional capping agent PhSppm⁷G^TMTrmM, m⁷G⁵pppGUUA and m⁷G^5′pppGUAUUA were synthesized from the corresponding oligoribonucleotide 5′-monophosphate derivatives. Since the latter was obtained in low yield because of poor solubility of the partially protected pUUA in DMF, the oligomer component was converted into a phosphorimidazolidate species which was found to be soluble in DMF and allowed to react with a newly designed capping agent, ppm⁷G^TMTrmM. This triphosphate bond formation proceeded smoothly to give m⁷G^5′pppGUAUUA in good yield.