[C:1]([NH:4][CH:5]([C:16]([OH:18])=[O:17])[CH2:6][C:7]1[CH:12]=[CH:11][C:10]([CH3:13])=[C:9]([O:14][CH3:15])[CH:8]=1)(=[O:3])[CH3:2].[OH-].[Na+]>O.O.O.O.O.O.[Co](Cl)Cl.O>[C:1]([NH:4][C@@H:5]([C:16]([OH:18])=[O:17])[CH2:6][C:7]1[CH:12]=[CH:11][C:10]([CH3:13])=[C:9]([O:14][CH3:15])[CH:8]=1)(=[O:3])[CH3:2]N-Acetyl-3-methoxy-4-methyl-DL-phenylalanine (7.28 g) was dissolved into a mixture of water (36.5 ml) and 1N sodium hydroxide solution (29 ml). Cobalt(II) chloride hexahydrate (36.5 mg) and acylase (Acylase Amano, 365 mg) were added to the solution and the mixture was stirred at 37° C. for 15.5 hours with controlling the pH of the reaction mixture to 7.5 with 1N sodium hydroxide solution. The insoluble material was removed by filtration and the pH of the filtrate was made to 3 with 6N hydrochloric acid, extracted with ethyl acetate, washed with water, dried over sodium sulfate, and evaporated in vacuo to give crude N-acetyl-3-methoxy-4-methyl-D-phenylalanine (3.17 g). The crude product was again subjected to the acylase reaction (cobalt(II) chloride hexahydrate 15.2 mg, acylase 152 mg, 37° C., pH 7.5, 20 hours) to give pure N-acetyl-3-methoxy-4-methyl-D-phenylalanine (2.70 g) as a viscous oil.
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