Reaction SMILES: [CH2:1]([O:3][C:4]([CH:6]([NH:16][C@H:17]([C:19]([OH:21])=[O:20])[CH3:18])[CH2:7][C:8](=O)[C:9]1[CH:14]=[CH:13][CH:12]=[CH:11][CH:10]=1)=[O:5])[CH3:2].C(O)C.[H][H]>O>[CH2:1]([O:3][C:4]([C@@H:6]([NH:16][C@H:17]([C:19]([OH:21])=[O:20])[CH3:18])[CH2:7][CH2:8][C:9]1[CH:14]=[CH:13][CH:12]=[CH:11][CH:10]=1)=[O:5])[CH3:2]
Reactant: CCOC(=O)C(CC(=O)c1ccccc1)N[C@@H](C)C(=O)O
Reactant: [H][H]
Solvent: O
Solvent: CCO
Product: CCOC(=O)[C@H](CCc1ccccc1)N[C@@H](C)C(=O)O
Yield: 75 %

Procedure:
N-(1-ethoxycarbonyl-3-oxo-3-phenylpropyl)-L-alanine [(1S/1R)=90/10] (100 g, 0.34 mole) is dissolved in 1100 ml of a 5 to 15% (w/w) water-containing ethanol containing 2 N sulfuric acid (substrate concentration: 0.3 mol/L, amount of sulfuric acid based on substrate: 6 equivalents). Thereto 5% Pd--C (20 g) is added, and immediately after the addition, the obtained mixture is sufficiently mixed and dispersed with supplying a sufficient amount of hydrogen at an agitation power of a 15 range from 0.5 to 1 kW/m3 under the pressure of a range from atmospheric pressure to 0.5 kg/cm2G, and reacted at a range from 20° to 25° C. While the reaction is monitored with HPLC, supply of hydrogen is stopped at the time when hydrogen is absorbed in an extent from 90% of the required amount to somewhat more. Then, the atmosphere is rapidly replaced with an inert gas such as nitrogen gas to stop the reaction. The time required for reaction is at most 10 hours. Pd--C is rapidly removed by filtration and the Pd--C cake is washed with a 5 to 10% (w/w) water-containing ethanol in the amount within a range from the same volume as that of the Pd--C cake to two-fold volume. After 250 ml of water is added to the resulting filtrate, the filtrate was neutralized (pH 4.5) by slowly adding dropwise an aqueous 30% (w/w) sodium hydroxide solution so that an inner temperature does not exceed a range from 20° to 30° C. The filtrate is concentrated at the inner temperature of a range from 50° to 60° C. under reduced pressure, and then concentrated under reduced pressure with appropriately adding water to crystallize slowly with replacing with water. Finally, the ethanol content is at most 2% (w/w), the sodium sulfate content is 10% (w/w) and the pH is 5.0. After cooling to an inner temperature of a range from 20° to 25° C., the resulting crystals are separated with centrifugal separator to eliminate the filtrate sufficiently. The crystals are washed with water in a 2-fold amount of the cake and water is allowed to eliminate sufficiently to obtain N-(1(S)-ethoxycarbonyl-3-phenylpropyl)-L-alanine crystals having good quality (water content: 15 to 20% (w/w) (wet basis) (yield: 75 to 80%). The quality after vacuum drying (40° to 70° C., 30 mmHg to 0.1 mmHg) is as follows: HPLC purity: not less than 99% (w/w), the content of N-(1(R)-ethoxycarbonyl-3-phenylpropyl)-L-alanine: not more than 0.1% (w/w), the content of N-(1-ethoxycarbonyl-3-cyclohexylpropyl)-L-alanine: not more than 0.1% (w/w), the content of N-(1-carboxy-3-phenylpropyl)-L-alanine: not more than 0.1% (w/w), the residue on ignition (residual substance obtained after ashing at a temperature of about 600° C.): not more than 0.1% (w/w).