Efficient synthesis of 2'-C-beta-methylguanosine.

2'-beta-Methyl nucleosides have potential value as therapeutic agents and as nucleoside analogues for exploring RNA biology. Here we develop a strategy for efficient synthesis for 2'-C-beta-methylguanosine (3). Starting from 1,2,3,5-tetra-O-benzoyl-2-C-beta-methyl-d-ribofuranose (1) and N2-acetylguanine, we obtained the title compound in two steps (78% overall yield) with high stereoselectivity (beta/alpha > 99:1) and high regioselectivity (N9/N7 > 99:1). Extension of this strategy to the classic synthesis of guanosine also resulted in high stereoselectivity (beta/alpha = 99:1) and improved regioselectivity (N9/N7 = 97:3).