The conversion of the 2′,3′-O-isopropylidene derivative of 5-amino-1-β-D-ribofuranosylimidazole-4-carboxamide (AICA riboside) into 2′,3′-O-isopropylidene-isoguanosine
Abstract
Treatment of the putative methoxyacetyl thioureido derivative (14), which was prepared in two steps from 5-amino-1 -(2′,3′-O-isopropylidene-β-D-ribofuranosyl)imidazole-4-carboxamide (1), with mercury(II) perchlorate in the presence of pyridine in tetrahydrofuran solution at room temperature and then with methanolic ammonia gives the ureido nitrite (5); treatment of (15) with mercury(II) ions under the same conditions gives (17). When (5) is allowed to react with N1,N1,N3,N3-tetramethylguanidine and water in tetrahydrofuran at room temperature, 2′,3′-O-isopropylideneisoguanosine (6) is obtained in high yield; however, when (5) is heated, under reflux, with triethylamine in dioxane–water (9 : 1, v/v), the amino nitrite (23) is obtained in good yield.