Synthesis of 3‐Deaza‐2′‐deoxyadenosine and 3‐Deaza‐2′,3′‐dideoxyadenosine: Glycosylation of the 4‐Chloroimidazo[4,5‐ c ]pyridinyl Anion

The convergent syntheses of 3‐deazapurine 2′‐deoxy‐β‐ D ‐ribonucleosides and 2′,3′‐dideoxy‐ D ‐ribonucleosides, including 3‐deaza‐2′‐deoxyadenosine ( 1a ) and 3‐deaza‐2′,3′‐dideoxyadenosine ( 1b ) is described. The 4‐chloro‐l H ‐imidazo[4,5‐c]pyridinyl anion derived from 5 was reacted with either 2′‐deoxyhalogenose 6 or 2′,3′‐dideoxyhalogenose 10 yielding two regioisomeric (N 1 and N 3 ) glycosylation products. They were deprotected and converted into 4‐substituted imidazo[4,5‐c]pyridine 2′‐deoxy‐β‐ D ‐ribonucleosides and 2′,3′‐dideoxy‐ D ‐ribonucleosides. Compounds 1a and 1b proved to be more stable against proton‐catalyzed N ‐glycosylic bond hydrolysis than the parent purine nucleosides and were not deaminated by adenosine deaminase.