C(OC([NH:8][C@@H:9]([CH2:20][C:21]1[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=1)[C:10]([O:12][CH2:13][C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1)=[O:11])=O)(C)(C)C.[ClH:27]>C(OCC)C.O1CCOCC1>[ClH:27].[NH2:8][C@@H:9]([CH2:20][C:21]1[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=1)[C:10]([O:12][CH2:13][C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1)=[O:11]Benzyl (2S)-2-(tert-butoxycarbonylamino)-3-phenyl-propanoate (12.8 g, 36 mmol) was stirred in HCl, 2 M in diethyl ether (90 mL) and HCl, 4 M in dioxane (18 mL) and the resulting mixture was stirred overnight at room temperature. The mixture was then diluted with hexanes (100 mL) and filtered to collect the title compound (7.98 g, 76%) as a fine white powder. 1H NMR (CD3OD, 400 MHz): δ (ppm) 7.40-7.15 (m, 10H), 5.23 (s, 2H), 4.36-4.31 (m, 1H), 3.26-3.12 (m, 2H).
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