Synthesis, NMR and MS study of novel N-sulfonylated purine derivatives

Tosylation and mesylation of adenine (1) at room temperature give regiosele ctively 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-6-monosu lfonylated product 4. Two N-sulfonylated purine nucleoside derivatives 12 a nd 15 have also been prepared. 1D/2D NMR determined the site of sulfonylati on and the spatial arrangement of the substituents. MS spectra showed unexp ected rearrangement of protonated molecular ions that occurs upon the loss of SO2.