Synthesis of 2'-N-Methylamino-2'-deoxyguanosine and 2'-N,N- Dimethylamino-2-deoxyguanosine and Their Incorporation into RNA by Phosphoramidite Chemistry.

The 2'-hydroxyl groups within RNA contribute in essential ways to RNA structure and function. Previously, we designed an atomic mutation cycle (AMC) that uses ribonucleoside analogues bearing different C-2'-substituents, including --OCH3 -- NH2 -- NHMe, and --NMe2 to identify hydroxyl groups within RNA that donate functionally significant hydrogen bonds. To enable AMC analysis of the nucleophilic guanosine cofactor in the Tetrahymena ribozyme reaction and at other guanosines whose 2'-hydroxyl groups impart critical functional contributions, we describe here the syntheses of 2'-methylamino-2'-deoxyguanosine (GNHMe) and 2-N,N-dimethylainino-2'-deoxyguanosine (Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed.) and their corresponding phosphoramidites. The key step in obtaining the nucleosides involved SN2 displacement of 2'-β-triflate from an appropriate guanosine derivative by methylamine or dimethylamine. We readily obtained the Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. phosphoramidite and incorporated it into RNA However, the G-NHMC phosphoramidite posed a significantly greater challenge due to lack of a suitable -2'-NHMe protecting group. After testing several strategies, we established that allyloxycarbonyl (Alloc) provided suitable protection for 2'-N-methylamino group during the phosphoramidite synthesis and the subsequent RNA synthesis. This work enables AMC analysis of guanosine's 2'-hydroxyl group within RNA. [ABSTRACT FROM AUTHOR]