C(OC([N:8]1[CH2:13][CH2:12][N:11]([CH2:14][C@@H:15]2[O:29][C:19]3=[C:20]4[C:25](=[CH:26][CH:27]=[C:18]3[O:17][CH2:16]2)[N:24]=[C:23]([CH3:28])[CH:22]=[CH:21]4)[CH2:10][CH2:9]1)=O)(C)(C)C.Cl.[OH-].[Na+]>C(OCC)(=O)C.C(OCC)C.CO>[CH3:28][C:23]1[CH:22]=[CH:21][C:20]2[C:25](=[CH:26][CH:27]=[C:18]3[O:17][CH2:16][CH:15]([CH2:14][N:11]4[CH2:12][CH2:13][NH:8][CH2:9][CH2:10]4)[O:29][C:19]3=2)[N:24]=1
To an ice-cold solution of (2S)-4-(8-methyl-2,3-dihydro-[1,4]dioxino[2,3-f]quinolin-2-ylmethyl)-piperazine 1 carboxylic acid tert-butyl ester of Step A′ (0.550 g, 1.37 mmol) in ethyl acetate (8 mL) is added dropwise 1 M hydrochloric acid in diethyl ether (15 mL). The mixture is allowed to come to room temperature, diluted with methanol (10–15 mL) and warmed at 35° C. until the reaction is complete by TLC. The solvents are removed in vacuo and the residue is slurried in diethyl ether. The solid is collected and dried in vacuo. The free base is prepared by basifying an aqueous solution of the hydrochloride salt with concentrated aqueous sodium hydroxide, followed by extraction with dichloromethane. The title compound is obtained as a thick oil (quantitative yield).
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