Improved antitumor effects in 3'-branched homologs of 2'-deoxythioguanine. Synthesis and evaluation of thioguanine nucleosides of 2,3-dideoxy-3-(hydroxymethyl)-D-erythro-pentofuranose

The 3-(hydroxymethyl) branched homologue of 2-deoxyribofuranose was synthesized from the corresponding branched ribofuranose 2-O-(S-methyl dithiocarbonate) with tributyltin hydride in the first direct, one-step deoxygenation at C-2 of a ribofuranose. Nucleoside coupling afforded the corresponding 3'-branched 2'-deoxyribonucleosides of thioguanine. The alpha- and beta-nucleosides were equally inhibitory to growth of WI-L2 human lymphoblastoid cells, were phosphorylated and incorporated into the DNA of Mecca lymphosarcoma in mice to the same degree, and were more effective in these tests than the parent analogue alpha-2'-deoxythioguanosine. These results indicate that the hydroxy functions at the 3' and 5' positions of 2'-deoxynucleosides are interchangeable and that acceptance by the that the furanose ring oxygen and 2'-methylene are corresponding interchangeable, and that acceptance by the enzymes is improved if primary hydroxyls are provided at both the 3' and 5' positions.