C([Li])CCC.C(NC(C)C)(C)C.[CH3:13][C:14]1[CH:19]=[N:18][CH:17]=[CH:16][N:15]=1.[CH2:20]([O:22][C:23](=[O:27])[CH2:24][CH2:25]Br)[CH3:21]>C1COCC1>[CH2:20]([O:22][C:23](=[O:27])[CH2:24][CH2:25][CH2:13][C:14]1[CH:19]=[N:18][CH:17]=[CH:16][N:15]=1)[CH3:21]Butyllithium (1.6 M in hexane solution, 10 ml, 16 mmol) was added dropwise to a solution of diisopropylamine (2.25 ml, 16 mmol) in anhydrous THF (50 ml) at −20° C. under a nitrogen atmosphere. The mixture was stirred at −20° C. for 30 minutes and after cooling at −70° C. a solution of 2-methyl-pyrazine (1.47 ml, 16 mmol) in THF (10 ml) was added dropwise. After 15 minutes, a solution of 3-bromo-propionic acid ethyl ester (2.54 ml, 19.2 mmol) in THF (10 ml) was added and the mixture maintained at −70° C. for 2 hours and then stirred at room temperature overnight. The reaction was then quenched with a saturated solution of NH4Cl and extracted with ethyl acetate, the organic phase was dried (Na2SO4) and evaporated. The residue was purified by flash chromatography (hexane/ethyl acetate from 9/1 to 1/1 respectively) to give the title compound (1 g, 33% yield).
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