[N:1]1([C:10]([O:12][CH2:13][C:14]2[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=2)=[O:11])[CH2:9][CH2:8][CH2:7][CH2:6][C@@H:2]1[C:3](O)=[O:4].C([N:22](CC)CC)C.ClC(OCC(C)C)=O.N>C(OCC)(=O)C>[N:1]1([C:10]([O:12][CH2:13][C:14]2[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=2)=[O:11])[CH2:9][CH2:8][CH2:7][CH2:6][C@@H:2]1[C:3]([NH2:22])=[O:4]
13.15 g (50 mmoles) of Z-D-Pip-OH (L. Balaspiri et al.: Monatsh. Chem. 101, 177/1970/) are dissolved in 100 ml of ethyl acetate, 7.0 ml (50 mmoles) of triethylamine are added, and the solution is cooled to -20° C. 6.5 ml (50 mmoles) of isobutyl chloroformate are added dropwise to the stirred solution at the same temperature, thereafter the mixture is stirred for 15 minutes, and then gaseous ammonia is introduced into the mixture at -10° C. for 1.5 hours. The separated precipitate is filtered off, the filtrate is washed with n hydrochloric acid, n sodium hydrocarbonate solution and water, dried over anhydrous sodium sulfate and evaporated. The residue is crystallized from a mixture of ethyl acetate and ether to obtain 11.5 g (88%) of Z-D-Pip-NH2 ; m.p.: 114°-115° C., Rf2 =0.50, [α]D25 =+32.0° (c=1%, in methanol).
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