O1CCCC1.[Br:6][C:7]1[N:8]=[C:9]2[CH2:14][CH:13]([C:15]([O:17][CH3:18])=[O:16])[CH2:12][CH2:11][N:10]2[C:19]=1Br.C([Mg]Br)(C)C.O>C(OCC)(=O)C>[Br:6][C:7]1[N:8]=[C:9]2[CH2:14][CH:13]([C:15]([O:17][CH3:18])=[O:16])[CH2:12][CH2:11][N:10]2[CH:19]=1A tetrahydrofuran (150 ml) solution of the methyl 2,3-dibromo-5,6,7,8-tetrahydroimidazo[1,2-a]pyridine-7-carboxylate (13 g) obtained in (Example 2.7) <Step 1> was cooled to −35° C. Thereafter, isopropylmagnesium bromide (95 ml, 1 M tetrahydrofuran solution) was added to the solution over 20 minutes, while keeping the temperature at −30° C. or less, and the reaction solution was then stirred at −35° C. for 30 minutes. Thereafter, water (350 ml) and ethyl acetate (250 ml) were added to the reaction solution, and insoluble matters were then removed by filtration with Celite. Subsequently, the filtrate was separated into an organic layer and a water layer. The water layer was extracted with ethyl acetate (250 ml), and the organic layers were then gathered. The gathered organic layer was washed with a saturated saline, and the solvent was then distilled away under reduced pressure. The obtained residue was purified by silica gel column chromatography (silica gel:eluent; heptane:ethyl acetate=70:30-30:70), so as to obtain the title compound (6.8 g) in the form of a white solid.
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