Synthesis and biological evaluation of some novel 4′-Thio- -ribonucleosides with modified nucleobase moieties

1,2,3,5-Tetra-O-acetyl-4-thio-β- -ribofuranose (13) was synthesized by an improved five-step sequence starting from methyl α- -lyxopyranoside. Compound 13 was then converted to the corresponding -4′-thionucleosides 4–6 and 19 by a modified Vorbrüggen procedure. All of these nucleoside analogues were tested for their antitumour activity in vitro.