Starting from benzyl 3,5-di-O-benzyl-2-deoxy-1,4-dithio-D-erythro- pentofuranoside (4), the following 2'-deoxy nucleoside analogues have been synthesized: 4'-thiothymidine (8), 3'-azido-4'-thio- deoxythymidine (10), and (E)-5-(2-bromovinyl)-4'-thio-2'-deoxyuridine (22). The first compound is toxic, the second is not toxic nor has detectable biological activity, and the third is not toxic and has significant activity against some herpesviruses.