S(Cl)(Cl)=O.[CH3:5][O:6][C:7]1[CH:8]=[C:9]([CH2:15][C@@H:16]([C:18]([OH:20])=[O:19])[NH2:17])[CH:10]=[CH:11][C:12]=1[O:13][CH3:14].[CH3:21]O>C(Cl)Cl>[CH3:21][O:19][C:18](=[O:20])[C@@H:16]([NH2:17])[CH2:15][C:9]1[CH:10]=[CH:11][C:12]([O:13][CH3:14])=[C:7]([O:6][CH3:5])[CH:8]=1Thionyl chloride (3.2 g, 2.0 mL, 26.8 mmol) was added dropwise to a suspension 3-(3,4-dimethoxyphenyl)-L-alanine 1 (2.0 g, 8.9 mmol) in anhydrous MeOH (50 mL) at 0° C. under a nitrogen blanket. The mixture was slowly warmed to room temperature, then stirred for 72 hours. The solvent was removed under reduced pressure to provide a solid. The crude product was taken up in CH2Cl2, then washed with saturated NaHCO3 and saturated NaCl. The organic layer was dried over anhydrous Na2SO4, filtered and concentrated to yield a light brown oil (1.97 g, 93%).
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