To a solution of Cyclopropyl-[3-methoxy-5-(3-methoxy-propoxy)-benzyl]-amine (1.18 g, 4.45 mmol) and triethylamine (0.68 mL, 4.90 mmol) in THF (20 mL) at room temperature is added 2,4-Dioxo-3-oxa-7-aza-bicyclo[3.3.1]nonane-7-carboxylic acid tert-butyl ester (1.07 g, 4.19 mmol). After stirred for 2 h, bulk of the solvent is concentrated. The residue is diluted with EtOAc, and washed with aq. KHSO4, water, and brine, dried over Na2SO4, filtered, and concentrated. To a solution of a part of the residue (673 mg, 1.29 mmol) in toluene (5 mL) at room temperature are added triethylamine (0.2 mL, 1.44 mmol) and DPPA (0.31 mL, 1.43 mmol). After stirred for 40 min, TMSCH2CH2OH (0.9 mL, 6.31 mmol) is added. The reaction mixture is refluxed for 2 h. After dilution with EtOAc, the mixture is washed with aq. KHSO4, water, aq. sat. NaHCO3, and brine, dried over Na2SO4, filtered, and concentrated. The residue is purified by silica gel column chromatography to afford the desired carbamate (332 mg, 0.522 mmol), which is treated with TBAF (410 mg, 1.57 mmol) in THF (5 mL) at 50° C. for 2.5 h. After dilution with EtOAc, the mixture is washed with water (×2) and brine, dried over Na2SO4, filtered, and concentrated to afford the title compound as a pale yellow oil. MS: 491 [M+H]+; tR (HPLC, ACQUITY UPLC™ BEH C18 1.7 μm, 50×2.1 mm; 5-100% CH3CN+0.1% TFA/H2O+0.1% TFA for 2 min then 100% CH3CN+0.1% TFA for 1 min, flow 0.5 ml/min): 1.67 min.
