[CH2:1]([O:8][C:9]([NH:11][C@H:12]([C:14]([OH:16])=O)[CH3:13])=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.C(N1CC[O:22]CC1)C.C(Cl)(=O)C(C)(C)C.Br.C(N[C:36](=[O:40])[C@H:37]([CH3:39])[NH2:38])C>O1CCCC1.CN(C)C=O>[CH2:1]([O:8][C:9]([NH:11][C@H:12]([C:14]([NH:38][C@H:37]([C:36]([OH:40])=[O:22])[CH3:39])=[O:16])[CH3:13])=[O:10])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=17.5 g (0.034 mol) of N-benzyloxycarbonyl-L-alanine were dissolved in 50 ml of dry tetrahydrofuran and the solution was cooled to -5° C. 4.26 ml (0.034 mol) of N-ethylmorpholine and 4.14 ml (0.034 mol) of pivaloyl chloride were then added and the solution was stirred at -5° C. for 30 minutes. To this mixture was then added a solution of 7.0 g (0.034 mol) of L-alanine ethylamide hydrobromide in 50 ml of dimethylformamide followed by 8.5 ml (0.068 mol) of N-ethylmorpholine. The solution was stirred at -10° C. for 1 hour and then left to stand for 16 hours at room temperature. The solvents were removed by evaporation; the product crystallising on the addition of water. The yield of N-benzyloxycarbonyl-L-alanyl-L-alanine obtained was 9.05 g (83%); melting point 203°-205° C.; [α]D20 =-1.1° (c=1.02% in dimethylformamide; [α] 36520 =-9.2° (c=1.02% in dimethylformamide).
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