Uracil Derivatives. IV. Growth-Inhibitory Activity against L-1210 Cells of Orotic Acid Derivatives and Synthesis of 1-(β-D-Ribofuranosyl) furo [3, 4-d] pyrimidine-2, 4, 7 (1H, 3H, 5H)-trione

5-(Substituted thiomethyl)-6-carbamoyluracils (IIIb-h) and 5-(substituted thiomethyl)-uracils (Va-h) were prepared and their ability to inhibit the growth of L-1210 cells in vitro was examined. The reaction of silylated furo [3, 4-d] pyrimidine-2, 4, 7 (1H, 3H, 5H)-trione (VI) with 1-O-acetyl-2, 3, 5-tri-O-benzoyl-β-D-ribofuranose (VII) in acetonitrile in the presence of SnCl4 gave 1-(2, 3, 5-tri-O-benzoyl-β-D-ribofuranosyl) furo [3, 4-d] pyrimidine-2, 4, 7 (1H, 3H, 5H)-trione (VIII) in 81.0% yield. The protected nucleoside (VIII) was hydrolyzed by sodium methoxide to give the N1-nucleoside (X).