Crude (2-{4-[5-(5-diethylaminomethyl-4-methyl-thiophen-2-yl)-[1,2,4]oxadiazol-3-yl]-benzenesulfonylamino}-ethyl)-carbamic acid tert-butyl ester (156 mg) is obtained starting from {2-[4-(N-hydroxycarbamimidoyl)-benzenesulfonylamino]-ethyl}-carbamic acid tert-butyl ester (277 mg, 0.774 mmol) and 5-diethylaminomethyl-4-methyl-thiophene-2-carboxylic acid (160 mg, 0.704 mmol) according to Method A; LC-MS: tR=0.61 min; [M+1]+=550.16. This material (156 mg, 0.284 mmol) is dissolved in 4 M HCl in dioxane (5 mL) and the mixture is stirred at rt for 18 h. The mixture is diluted with water and washed with EA. The organic washing is extracted with water. The combined aq. extracts are neutralised by adding sat. aq. NaHCO3 solution and extracted twice with EA. These organic extracts are combined, dried over MgSO4, filtered and concentrated. The crude product is purified by prep. HPLC (XBridge, eluting with a gradient of acetonitrile in water containing 0.5% of aq. ammonia) to give the title compound (11 mg) as a pale yellow oil; LC-MS: tR=0.42 min; [M+1]+=449.64.
