Convergent syntheses and cytostatic properties of 2-chloro-2′-deoxy-2′-fluoroadenosine and its N7-isomer

Glycosylation of trimethylsilylated 2,6-dichloropurine 2 with acetate 1 in anhydrous MeCN was investigated. In the presence of SnCl4, the reaction was regio- and stereoselective affording N7-β-glycoside 3 (86%). The use of TMS-Tfl instead of SnCl4 afforded a ≈ 9:1 mixture of the N9-β- and -α-glycosides 5 and 6 (90%, combined). The title nucleosides were tested for their cytotoxicity.