Cl.Cl.[NH:3]1[CH2:8][CH2:7][NH:6][CH2:5][CH:4]1[C:9]([OH:11])=[O:10].[OH-].[Na+].[C:14]([O:18][C:19](ON=C(C1C=CC=CC=1)C#N)=[O:20])([CH3:17])([CH3:16])[CH3:15]>O1CCOCC1.O.O1CCOCC1>[C:19]([N:6]1[CH2:7][CH2:8][NH:3][CH:4]([C:9]([OH:11])=[O:10])[CH2:5]1)([O:18][C:14]([CH3:17])([CH3:16])[CH3:15])=[O:20]piperazine-2-carboxylic acid dihydrochloride (10.0 g, 49.23 mmol) is dissolved in 1:1 dioxane/water (320 ml). 50% Aqueous sodium hydroxide is added to bring the pH to 11. BOC-ON (2-(tert-butoxycarbonyloxyimino)-2-phenylacetonitrile), (15.59 g, 63.32 mmol) is dissolved in dioxane (80 ml) and added dropwise while maintaining the pH at 11 with 50% aqueous sodium hydroxide. The reaction is stirred overnight at ambient temperature. The reaction mixture is then extracted with diethyl ether (5×250 ml) and acidified to pH 2 with concentrated hydrochloric acid. The di-Boc compound is then extracted out with ethyl acetate (4×200 ml) and the acidic aqueous solution containing the desired mono-Boc product is then taken on in the synthesis.
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