[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 1.0N 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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