[CH2:1]([O:3][C:4](=[O:24])[CH2:5][C:6](=C=O)[C@@H:7]([C:19](=O)[NH2:20])[NH:8][C:9]([O:11][CH2:12][C:13]1[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1)=[O:10])[CH3:2].N1C=CC=CC=1.FC(F)(F)C(OC(=O)C(F)(F)F)=O>O1CCCC1>[C:9]([NH:8][CH:7]([C:19]#[N:20])[CH2:6][CH2:5][C:4]([O:3][CH2:1][CH3:2])=[O:24])([O:11][CH2:12][C:13]1[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1)=[O:10]To a suspension of 21.45 g of N-carbobenzoxy-carbonyl-L-isoglutamine ethyl ester in 200 mL of dry tetrahydrofuran kept at 0° C. to -5° C. in an ice-bath 11.82 mL of pyridine is added. To the above solution 9.84 mL of trifluoroacetic anhydride in 100 mL of tetrahydrofuran is added dropwise at such a rate that the bath temperature is maintained. The solution is stirred for 2 hours at this temperature. The solution is evaporated to dryness and the oil is dissolved in ethyl acetate. The organic layer is washed with 1.0 N hydrochloric acid and sterile water. The solution is dried and evaporated in vacuo to give an oil to give 14.8 g of ethyl γ-(N-carbobenzoxy)amino-γ-cyanobutanoate, 17.
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