Stereoselective synthesis of 9-β-d-arabianofuranosyl guanine and 2-amino-9-(β-d-arabianofuranosyl)purine

9-β-d-Arabianofuranosyl guanine (6) and 2-amino-9-(β-d-arabianofuranosyl)purine (8) were prepared from 2-amino-6-chloro-9-(2,3,5-triphenylmethoxyl-β-d-arabianofuranosyl)purine (4), a key intermediate which was stereoselectively prepared from 2,3,5-triphenylmethoxyl-d-arabianofuranose and 2-amino-6-chloro-purine. The yield of the intermediate was obviously improved and only β-isomer was formed by using the activated molecular sieve as environmental friendly catalyst, overcoming the defect that a 1:1 mixture of α- and β-isomers was formed, which was difficult to separate, when toxic mercury cyanide was previously used as catalyst.