Purines. LXI. An Attempted Synthesis of 2'-Deoxy-7-methyladenosine: Glycosidic Hydrolyses of the N6-Methoxy Derivative and 2'-Deoxy-NX-methyladenosines

In an attempt to synthesize 2'-deoxy-7-methyladenosine (5b), 2'-deoxy-N6-methoxyadenosine (13b) was treated with MeI in AcNMe2 at 0°C for 7h to give the 2'-deoxy-N6-methoxy-7-methyladenosine salt (14b), which was unstable and easily underwent glycosidic hydrolysis in H2O at 16-18°C to form N6-methoxy-7-methyladenine (15). On account of such instability, hydrogenolysis of 14b in H2O using hydrogen and Raney Ni catalyst failed to afford the desired nucleoside (5b). 2'-Deoxy-N6-methyladenosine (2b), 2'-deoxy-1-methyladenosine (3b), and 14b were found to undergo glycosdic hydrolysis in 0.1 N aqueous HCl at 25°C at rates of 7.92×10-3 min-1 (half-life 87.5 min), 5.02×10-3 min-1 (half-life 138 min), and 2.31×10-2 min-1 (half-life 30.0 min), respectively, while the rate in the case of 5b was roughly estimated to be ca. 2 min-1 (half-life 0.35 min).