[C:1]([O:5][C:6]([NH:8][C@H:9]([C:17]([O:19]C1C(F)=C(F)C(F)=C(F)C=1F)=O)[CH2:10][C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1)=[O:7])([CH3:4])([CH3:3])[CH3:2].[NH2:31][CH2:32][C:33]([O:35][CH2:36][CH3:37])=[O:34].C(N(CC)CC)C>O1CCOCC1.C(OCC)(=O)C>[C:6]([NH:8][C@H:9]([C:17]([NH:31][CH2:32][C:33]([O:35][CH2:36][CH3:37])=[O:34])=[O:19])[CH2:10][C:11]1[CH:12]=[CH:13][CH:14]=[CH:15][CH:16]=1)([O:5][C:1]([CH3:2])([CH3:3])[CH3:4])=[O:7]To a solution of 0.86 g (2 mmol) of pentafluorophenyl N-t-butyloxycarbonyl-L-phenylalaninate, prepared according to Example 48, in 10 ml of dioxane, 0.28 g (2.2 mmol) of ethyl glycinate (hydrochloride) and 0.31 g (3 mmol) of triethylamine are added simultaneously. The mixture is stirred for one hour at room temperature. It is diluted with 10 ml of ethyl acetate and washed with aqueous 0.1N hydrochloric acid, potassium bicarbonate and sodium chloride solutions. The organic phase is dried over magnesium sulphate and evaporated. The residue is taken up with a 4:6 ethyl acetate/hexane mixture and filtered on silica. After evaporation, 0.53 g (Y=76%) of BOC-Phe-Gly-OEt is obtained.
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