Nucleic acid related compounds. 33. Conversions of adenosine and guanosine to 2,6-dichloro, 2-amino-6-chloro, and derived purine nucleosides

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Abstract
Enzymatic deamination of adenosine 1-N-oxide gave 1-hydroxyinosine (2a) which was acetylated and then chlorinated to give 2,6-dichloro-9-(2,3,5-tri-O-acetyl-(β-D-ribofuranosyl)purine (3). Ammonia in dry 1,2-dimethoxyethane converted 3 into 2-chloro-adenosine triacetate (4a). Treatment of 4a with trimethylamine at elevated temperatures in acetonitrile resulted in formation of 2-N,N-dimethylaminoadenosine triacetate (4b). Guanosine (5) was acetylated smoothly by an improved procedure. The resulting triacetate (6) was chlorinated in ∼85% yield to give 2-amino-6-chloro-9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)purine (7). Treatment of 7 with trimethylamine at ambient temperature for 28 hours gave the 6-N,N-dimethylamino compound (8d). However, potassium fluoride or sodium azide with catalytic quantities of trimethylamine in DMF or acetonitrile gave the 2-amino-6-fluoro (8a) or 2-amino-6-azido (8b) products in yields of greater than 90%.