Synthesis of 5'-terminal capped oligonucleotides using O-N phosphoryl migration of phosphoramidite derivatives.

Trivalent phosphoramidite derivatives could be readily converted by reacting with 1-hydroxy-7-azabenzotriazole to phosphotriester intermediates; these intermediates reacted smoothly with phosphorylated compounds to give pyrophosphate derivatives. This new phosphorylation approach enabled a facile and rapid synthesis of 5′-adenylated DNA oligomers (A5′ppDNA) on resins using a silyl-type linker. Our new approach could be applied to the synthesis of a 2′-OMe-RNA oligomer containing the 5′-terminal 2,2,7-trimethylguanosine cap structure.