[S:1]1[CH:5]=[CH:4][CH:3]=[C:2]1[CH2:6][CH:7]([C:9]([OH:11])=[O:10])[NH2:8].C([O-])([O-])=O.[K+].[K+].[C:18](Cl)([O:20][CH2:21][C:22]1[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=1)=[O:19].CCOC(C)=O.CC(O)=O.CC#N.O>O>[CH2:21]([O:20][C:18]([NH:8][CH:7]([C:9]([OH:11])=[O:10])[CH2:6][C:2]1[S:1][CH:5]=[CH:4][CH:3]=1)=[O:19])[C:22]1[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=1
Into a 500 ml flask was placed 3.0 g of 3-(2-thienyl)-D,L-alanine (optically active material in the L-form is available from Aldrich or SIGMA and could be used to obtain an optically active product) in 75 ml H2O/60 ml dioxane, and 5.6 g K2CO3 was added, followed by 2.85 ml of carbobenzyloxy chloride. The mixture was stirred rapidly for 1 hour. TLC (21/7/7/9, EtOAc/AcOH/CH3CN/H2O) showed that the starting material was gone. A new higher Rf product was seen. The dioxane was concentrated off and the aqueous layer was washed with Et2O (75 ml). The aqueous layer was mixed with CH2Cl2 (150 ml) and acidified to pH=2.0 with 5 N HCl. The desired N-(Benzyloxycarbonyl)-3-(2-thienyl)-D,L-alanine was extracted with CH2Cl2. The organic layer was separated and dried with Na2SO4, filtered, and concentrated to give 5.05 g of desired N-(Benzyloxycarbonyl)-3-(2-thienyl)-D,L-alanine (98% yield).
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