合成路线1

Further nitration of the nitroimidazole (I) with HNO3, Ac2O gives the 1,4-dinitroimidazole (II), which is treated with KCN and NaHCO3 in methanol/water to yield 5-nitro-1H-imidazole-4-carbonitrile (III). The reaction of (III) with dihydropyran and Ts-OH in ethyl acetate affords the N-protected imidazole (IV). The reduction of (IV) with H2 over Pt/C in ethyl acetate provides the hydroxylamine (V), which is oxidized with NaIO4 in ethyl acetate/water to give the nitroso derivative (VI). The condensation of (VI) with phenyl 2-methylcarbazate (VII) by means of HOAc and TFA yields the triazene (VIII), which is treated with conc. HCL in ethyl acetate to afford the carboxamide (IX). Finally, this compound is cyclized to the target imidazo-tetrazinone by irradiation with daylight in acetone/MeOH, most probably through the non isolated cis intermediate (X).