Conversion of guanosine into isoguanosine and derivatives

Abstract

Treatment of 2-amino-6-chloro-9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)purine 7, which is readily prepared from guanosine 2 in two steps, with toluene-4-thiol and triethylamine followed by sodium nitrite in aqueous acetic acid gives 6-[(4-methylphenyl)thio]-2-oxo-9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)-2,3-dihydropurine 9. When the latter compound (9) is treated with ammonia in aqueous ethanol at 70 °C, methylamine in industrial methylated spirit at room temperature, dimethylamine in industrial methylated spirit at 50 °C, and aniline, under reflux, in pyridine solution followed by methanolic ammonia at room temperature, isoguanosine 1,6-N-methylisoguanosine 12a, 6,6-di-N-methylisoguanosine 12b, and 6-N-phenylisoguanosine 12c, respectively, are obtained in satisfactory yields.