[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][CH2:11][CH2:10][CH:9]1[C:14]([OH:16])=O)=[O:7])([CH3:4])([CH3:3])[CH3:2].C(N(CC)CC)C.ClC(OCC(C)C)=O.[C:32]([C:34]1[CH:35]=[C:36]([CH:41]=[CH:42][CH:43]=1)[C:37]([NH:39]O)=[NH:38])#[N:33]>C1COCC1.ClCCl.O.CN(C=O)C>[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][CH2:11][CH2:10][CH:9]1[C:14]1[O:16][N:39]=[C:37]([C:36]2[CH:41]=[CH:42][CH:43]=[C:34]([C:32]#[N:33])[CH:35]=2)[N:38]=1)=[O:7])([CH3:2])([CH3:3])[CH3:4]To a mixture of piperidine-1,2-dicarboxylic acid 1-tert-butyl ester (5.32 g, 23.2 mmol) and triethylamine (4.04 g, 40 mmol) in THF (50 mL), isobutyl chloroformate (3.0 mL, 25.5 mmol) was added dropwise. After the mixture was stirred at room temperature for 45 min, 3-cyano-N-hydroxy-benzamidine (3.7 g, 23.2 mmol) and DMF (40 mL) were added. After being stirred for another hour, the reaction mixture was heated to 130˜135° C. for 1.5 h. Then the solution was cooled to room temperature and poured into water. Dichloromethane was used to extract the product. The organic layer was dried with sodium sulfate and concentrated in vacuo to give 8.1 g (98.4%) of the title compound as a thick brown oil.
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