[C:1]([NH:11][C@H:12]([C:15]([OH:17])=[O:16])[CH2:13]Cl)([O:3][CH2:4][C:5]1[CH:10]=[CH:9][CH:8]=[CH:7][CH:6]=1)=[O:2].C(=O)([O-])O.[Na+].[C:23]1([SH:29])[CH:28]=[CH:27][CH:26]=[CH:25][CH:24]=1.Cl>O>[C:1]([NH:11][C@H:12]([C:15]([OH:17])=[O:16])[CH2:13][S:29][C:23]1[CH:28]=[CH:27][CH:26]=[CH:25][CH:24]=1)([O:3][CH2:4][C:5]1[CH:10]=[CH:9][CH:8]=[CH:7][CH:6]=1)=[O:2]N-Carbobenzyloxy-β-chloro-L-alanine (0.091 g, 0.35 mmol) was dissolved in 0.45 ml of water and, then, 0.065 g (0.77 mmol) of sodium hydrogen carbonate was added. Thereafter, 0.046 g (0.42 mmol) of thiophenol was added dropwise at room temperature in a nitrogen gas atmosphere. After 2 hours of stirring at 60° C., the reaction mixture was cooled with ice and acidified with 1 N hydrochloric acid, and then extracted with ethyl acetate. The solvent was distilled off and the residue was purified by column chromatography to give 0.097 g (0.29mmol, 84%) of N-carbobenzyloxy-S-phenyl-L-cysteine. The product obtained had an optical purity of not less than 98% e.e. as determined by HPLC analysis following the same procedure as in Example 13.
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