[CH:1]1([CH2:4][NH:5][C:6]2[C:7]([NH2:14])=[CH:8][C:9]([O:12][CH3:13])=[CH:10][CH:11]=2)[CH2:3][CH2:2]1.CS(O)(=O)=O.[N:20](OCCC(C)C)=O>C(O)C.C(OCC)(=O)C>[CH:1]1([CH2:4][N:5]2[C:6]3[CH:11]=[CH:10][C:9]([O:12][CH3:13])=[CH:8][C:7]=3[N:14]=[N:20]2)[CH2:2][CH2:3]1N1-(Cyclopropylmethyl)-4-methoxybenzene-1,2-diamine (8-2, 10.8 g, 56.2 mmol) was dissolved in ethanol (80 mL) and treated with methanesulfonic acid (3.65 ml, 56.2 mmol) followed by isoamyl nitrite (7.56 ml, 56.2 mmol). The mixture was stirred for 15 minutes, diluted with ethyl acetate (1500 mL) and washed with saturated bicarbonate solution (500 mL×2). The organic extracts were concentrated in vacuo. The residue was purified by silica gel gradient chromatography (5-50% ethyl acetate in heptanes), providing the titled compound 8-3 as a tan solid.
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