[NH2:1][CH2:2][CH2:3][CH2:4][C:5]([OH:7])=[O:6].[CH2:8]([O:15][C:16](Cl)=[O:17])[C:9]1[CH:14]=[CH:13][CH:12]=[CH:11][CH:10]=1.[OH-].[Na+].O1CCC[CH2:22]1>O.CO.C(OCC)(=O)C>[CH2:8]([O:15][C:16]([NH:1][CH2:2][CH2:3][CH2:4][C:5]([O:7][CH3:22])=[O:6])=[O:17])[C:9]1[CH:14]=[CH:13][CH:12]=[CH:11][CH:10]=14-Aminobutyric acid (7.5 g) was dissolved in a mixture of tetrahydrofuran (80 ml) and water (80 ml), which was cooled at 0° to 5° C. in an ice bath. To a resulting mixture was added dropwise benzyloxycarbonyl chloride (10.4 ml) with maintaining the pH from pH 8.0 to 9.0 with 30% aqueous sodium hydroxide solution at 0° to 5° C. The reaction mixture was washed with ethyl acetate (300 ml) and aqueous layer was separated, which was adjusted to pH 1.0 with 6N-aqueous hydrochloric acid and extracted with ethyl acetate (300 ml). Organic layer was separated, washed with brine (100 ml×2) and dried over magnesium sulfate. Evaporation of the solvent gave a residue, which was dissolved in methanol (200 ml) and added conc. sulfic acid (1 ml). The resulting solution was refluxed for 3 hours. Evaporation of the solvent gave a residue, which was dissolved in ethyl acetate (300 ml), washed in turn with water (100 ml), saturated sodium hydrogen carbonate in water (100 ml×3) and brine (100 ml×2), and dried over magnesium sulfate. Solvent was removed under reduced pressure to give methyl 4-(benzyloxycarbonylamino)butyrate (14.65 g).
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