[NH2:1][C:2]1[N:3]=[C:4]([C:11]2[O:12][CH:13]=[CH:14][CH:15]=2)[C:5]([C:8](=O)[CH3:9])=[N:6][CH:7]=1.[C:16](O)(=O)C.[CH:20]([NH2:22])=[NH:21]>COC(OC)N(C)C.C(O)C.C1(C)C=CC=CC=1>[O:12]1[CH:13]=[CH:14][CH:15]=[C:11]1[C:4]1[N:3]=[C:2]([NH2:1])[CH:7]=[N:6][C:5]=1[C:8]1[CH:9]=[CH:16][N:22]=[CH:20][N:21]=1A solution of 1-[5-amino-3-(2-furyl)pyrazin-2-yl]ethanone (Preparation 4, 388 mg, 1.91 mmol) in N,N-dimethylformamide dimethyl acetal (1.3 mL) was heated to 100° C. After 9 h, the mixture was concentrated under reduced pressure to yield brown oil. Formamidine acetate (795 mg, 7.64 mmol) was added to this oily residue previously dissolved in ethanol (6.4 mL) and toluene (0.96 mL). Molecular sieves (4 Å) were added to the solution and the whole reaction mixture was heated to 115° C. in a sealed tube and stirred for 20 h. The crude reaction was filtered and concentrated to dryness. The residue was partitioned between ethyl acetate and water, the organic layer was washed with brine, dried (Na2SO4) and evaporated. The residue was purified by silica gel flash chromatography (100% ethyl acetate). Concentration in vacuo of the product-rich fractions provided the titled compound as a pale-yellow solid (137 mg, 30%).
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