抄録
Development of effective methods for the synthesis of modified oligonucleotides having various functional groups is highly desirable today. Recently, we developed O-selective phosphorylation named the proton-block method and the activated phosphite method to synthesize modified DNA oligonucleotide having alkaline-labile functional groups. In RNA synthesis without base protection, it was found that O-selectivity of the phosphorylation with P-N bond cleavage using 6-nitro-HOBt was more than 99%. Additionally, development of new protecting groups, which can be removed under mild conditions, such as AzMB, PSC and amidine-type groups was carried out. Furthermore, we developed the effective pyrophosphorylation using O-N phosphoryl rearrangement of phosphoramidite compound mediated by HOBt derivative. This new pyrophosphorylation could be applied to the synthesis of adenylpyrophosphoryl capped and 5’-terminal m32,2,7Gppp capped oligonucleotides.
