C([O:3][C:4]([C:6]1[C:7]2[CH2:8][C@H:9]3[CH2:21][C@H:10]3[C:11]=2[N:12]([C:14]2[CH:19]=[C:18]([Br:20])[CH:17]=[CH:16][N:15]=2)[N:13]=1)=[O:5])C.[OH-].[Na+]>C1COCC1.CO>[Br:20][C:18]1[CH:17]=[CH:16][N:15]=[C:14]([N:12]2[C:11]3[C@@H:10]4[CH2:21][C@@H:9]4[CH2:8][C:7]=3[C:6]([C:4]([OH:5])=[O:3])=[N:13]2)[CH:19]=1
To a solution of (1aR,5aR)-2-(4-bromo-pyridin-2-yl)-1a,2,5,5a-tetrahydro-1H-2,3-diaza-cyclopropa[a]pentalene-4-carboxylic acid ethyl ester (9.0 g, 25.8 mmol) in THF (50 mL) and MeOH (50.0 mL) was added a 2.0 M aqueous solution of sodium hydroxide (25.8 mL, 51.7 mmol). The reaction was stirred at 23° C. for 2 h then concentrated to remove the organic solvents. The remaining residue was diluted to 150 mL with water. This solution was filtered to remove trace insoluble impurities then acidified to pH ˜3 with 6 M HCl. The resulting precipitate was collected by filtration, rinsed with water, then dried under vacuum to give the title compound (8.3 g) as a white solid. LCMS m/z=320.0 [M+H]+.
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