[CH2:1]([O:8][C:9]([NH:11][C@@H:12]([CH2:17][CH2:18][C:19]#[N:20])[C:13]([O:15][CH3:16])=[O:14])=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[N-:21]=[N+:22]=[N-:23].[Na+].Cl.C(N(CC)CC)C>C1(C)C=CC=CC=1>[CH2:1]([O:8][C:9]([NH:11][C@@H:12]([CH2:17][CH2:18][C:19]1[NH:23][N:22]=[N:21][N:20]=1)[C:13]([O:15][CH3:16])=[O:14])=[O:10])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1Into the same device as used in Example 1 were placed 77.3 g (0.28 mole) of methyl (2S)-2-benzyloxycarbonylamino-4-cyanobutyrate, 27.3 g (0.42 mole) of sodium azide, 57.7 g (0.42 mole) of triethylamine hydrochloride and 280 ml of toluene. Thereafter, the mixture was heated to a temperature of 82 to 83° C. to undergo a reaction for 24 hours. Subsequently the same procedure as in Example 1 was repeated, and crystals were collected by filtration. Further, the crystals were recrystallized from methanol and water, filtered and dried, giving 67.7 g (0.21 mole) of methyl (2S)-2-benzyloxycarbonylamino-4-(tetrazole-5-yl)butyrate (yield 75.8% based on methyl (2S)-2-benzyloxycarbonylamino-4-cyanobutyrate). The reaction is illustrated below with chemical formulas: ##STR27##
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