Synthesis and Biological Activity of 4′-Thionucleosides of 2-Chloroadenine1

1,2,3,5-Tetra-O-acetyl-4-thio-D-riboruranose, prepared from 2,3,5-tri-O-benzyl-D-ribofuranose in four steps, was converted to the corresponding 2-chloroadenine nucleoside (8), which was deoxygenated to obtain 2-chloro-2′-deoxy-4′-thioadenosine (12). This is the first report of a 2′-deoxy-4′-thioribonucleoside of a purine rather than a pyrimidine. These novel nucleosides (8 and 12) were cytotoric to several human tumor cell lines in culture.