Sažetak Tosylation and mesylation of adenine (1) at room temperature give regioselectively N 9-sulfonylated purines 2 and 5. Excess of TsCl or MsCl at higher reaction temperatures leads to formation of unstable N 6, N 9-disulfonylated products 3 and 6, which easily transform into the corresponding N 9-monosulfonylated product 4. Two N-sulfonylated purine nucleoside derivatives 12 and 15 have also been prepared. 1D/2D NMR ...