[CH3:1][N:2]([C:4]([CH3:9])([CH3:8])[C:5]([OH:7])=[O:6])[CH3:3].Cl.N[C@H](C(N(C)[C@H](C(N1CCC[C@H]1C(N1CCC[C@H]1C(NCC1C=CC=CC=1)=O)=O)=O)C(C)C)=O)C(C)C.Cl.C(N(CC)CC)C>CN(C=O)C>[CH3:1][N:2]([C:4]([CH3:9])([CH3:8])[C:5]([OH:7])=[O:6])[CH3:3]
Preparation of Me2Aib-Val-MeVal-Pro-Pro-NHBn×HCl 2-[N,N-Dimethylamino]-isobutyric acid (1.3 g, 10 mmol) and 5.5 g (10 mmol) H-Val-MeVal-Pro-Pro-NHBn×HCl were dissolved in 50 ml dry DMF. After cooling to 0° C., 1.6 g DEPCN (10 mmol) and 2.9 ml triethylamine were added to the reaction mixture. The resulting mixture was stirred at 0° C. for 2 h and at room temperature overnight. Ice water (50 mL) was then added, and the resulting mixture was extracted twice with diethyl ether. The ether extracts were washed with 1 N NaOH (1×) and aqueous NaCl (3×), then dried over sodium sulfate and evaporated to dryness under reduced pressure. The product was crystallized from 100 ml diethyl ether with HCl/ether, and recrystallized from acetone to give 1.2 g of the desired product, which was characterized by fast atom bombardment mass spectrometry ([M+H]+=627).
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