Synthesis and properties of 2-nitrosoadenosine

A series of new 2-substituted adenosine derivatives was synthesised via add ition and condensation reactions with 2-nitrosoadenosine triacetate 4. The exceptional reactivity of the adenosine nitroso functionality was demonstra ted by reaction with, e.g., dienes (4 + 2 cycloaddition), cyclohexene ('ene ' reaction), furans (addition/rearrangement) and with anilines (Mills coupl ing). 2-Nitrosoadenosine triacetate was prepared from 6-chloropurine ribosi de triacetate via nitration at the 2-position followed by reduction/oxidati on of the nitro group. The vulnerable nitroso functionality of 4 had to be protected by 4 + 2 cycloaddition with cyclopentadiene to make deacylation o f the ribose ring possible. Retro-Diels-Alder reaction of the deacylated pr oduct at 95 degreesC gave the title compound 2-nitrosoadenosine 7. Dimerisa tion of the nitroso functionality of triacetate 4 was studied with H-1 NMR by changing the temperature, concentration and solvent. In particular, vari ation of temperature gave control over this dimerisation: 100% monomer at 6 5 degreesC gave complete dimerisation at -20 degreesC.