Cl.Cl.[NH:3]1[CH2:8][CH2:7][NH:6][CH2:5][CH:4]1[C:9]([OH:11])=[O:10].[OH-].[Na+].[CH3:14][C:15]([O:18][C:19](ON=C(C1C=CC=CC=1)C#N)=[O:20])([CH3:17])[CH3:16]>O.O1CCOCC1.O1CCOCC1>[C:15]([O:18][C:19]([N:6]1[CH2:7][CH2:8][NH:3][CH:4]([C:9]([OH:11])=[O:10])[CH2:5]1)=[O:20])([CH3:17])([CH3:16])[CH3:14]To a solution of 2-piperazine-carboxylic acid dihydrochloride (1.0 g, 4.92 mmol) in 20 mL of water/dioxane 1:1, NaOH 6N was added to adjust the pH to 11. A solution of BOC-ON (1.34 g, 5.41 mmol) in dioxane (5 mL) was then added dropwise, while maintaining the pH=11 during the addition and the resulting solution was stirred overnight at room temperature. Another 0.134 g of BOC-ON were added and the reaction mixture was stirred for 2 h. The solvent was evaporated under reduced pressure and the residue was diluted with diethyl ether/water (60 mL). The phases were separated and the pH of the aqueous layer was adjusted to 7 by slow addition of HCl 1N. Evaporation of water under reduced pressure afforded the title compound as a white solid which was dried in a vacuum oven at 50 C and used without further purification for the next step.
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