The preparation of the anomeric 9-(2-deoxy-D-enytho-pentofuranosyl)-2-fluoroadenines and 9-D-arabinofuranosyl-2-fluoroadenines from 2,6-dichloropurine is described. The cytotoxicity of these compounds, and also of 3′-deoxy-2-fluoroadenosine and 9-β-D-xylofuranosyl-2-fluoroadenine, to a number of HEp-2 cell lines in culture has been determined. The data permit certain conclusions concerning the probable metabolism and mechanism of action of these nucleosides. © 1969, American Chemical Society. All rights reserved.