6-Methylthiopurine ribonucleoside was found to inhibit nucleotide formation from hypoxanthine and aminoimidazole carboxamide in Ehrlich ascites tumor cells in vitro and to inhibit inosinate dehydrogenase activity in intact cells. These effects are produced at higher drug concentrations than required to inhibit purine biosynthesis de novo. 4-Methylthio-7-|8-D-ribofuranosyl pyrrolo[2,3-i/]pyrimid...

Purine nucleoside analogs modified by replacement of the nitrogen atom at the 3 position by a CH group give a characteristic circular dichroism curve that is not substantially modified by chemical substitution at the 8 position. Since it is rather well established that 8-substituted purine nucleosides are predominantly in the syn conformation in aqueous solution, it follows that the 3-deazapuri...

BACKGROUND Poly-substituted xanthine derivatives are an important class of compounds in medicinal chemistry. Substitution at the 8-position of the purine ring is generally accessible by ring closure of a carboxamido-substituted uracil precursor. Although several procedures to accomplish this synthetic step have been suggested, it still remains difficult in many cases. RESULTS Ring closure rea...