[CH2:1]([N:3]([CH2:6][C:7]1[S:11][C:10]([C:12]2[O:16][N:15]=[C:14]([C:17]3[CH:22]=[C:21]([CH3:23])[C:20]([OH:24])=[C:19]([CH2:25][CH3:26])[CH:18]=3)[N:13]=2)=[CH:9][C:8]=1[CH3:27])[CH2:4][CH3:5])[CH3:2].C([O-])([O-])=O.[K+].[K+].C([NH:41][CH2:42][CH2:43]Br)(OC(C)(C)C)=O>C(#N)C>[CH2:1]([N:3]([CH2:6][C:7]1[S:11][C:10]([C:12]2[O:16][N:15]=[C:14]([C:17]3[CH:22]=[C:21]([CH3:23])[C:20]([O:24][CH2:43][CH2:42][NH2:41])=[C:19]([CH2:25][CH3:26])[CH:18]=3)[N:13]=2)=[CH:9][C:8]=1[CH3:27])[CH2:4][CH3:5])[CH3:2]To a mixture of 4-[5-(5-diethylaminomethyl-4-methyl-thiophen-2-yl)-[1,2,4]oxadiazol-3-yl]-2-ethyl-6-methyl-phenol (700 mg, 1.82 mmol) and K2CO3 (760 mg, 5.45 mmol) in acetonitrile (14 mL), 2-(Boc-amino)-ethylbromide (839 mg, 3.63 mmol) is added. The mixture is stirred at 80° C. for 12 h. The mixture is filtered and the filtrate is concentrated. The residue is dissolved in DCM (10 mL) and treated with TFA (1.4 mL). The mixture is stirred at rt for 19 h before another portion of TFA (0.7 mL) is added. Stirring is continued at rt for another 21 h. The mixture is diluted with DCM and washed with 1 M aq. NaOH. The washing is extracted back with DCM. The combined organic extracts are dried over MgSO4, filtered and concentrated. The crude product is purified by prep. HPLC. The product containing fractions are combined, concentrated, dissolved in methanol:water 9:1 and filtered over Amberlyst A-21. The filtrate is evaporated and dried to give the title compound (513 mg) as a pale yellow resin; LC-MS: tR=0.44 min; [M+1]+=429.20; 1H NMR (D6-DMSO): δ1.03 (t, J=7.0 Hz, 6H), 1.23 (t, J=7.5 Hz, 3H), 2.22 (s, 3H), 2.35 (s, 3H), 2.58 (q, J=7.3 Hz, 4H), 2.73 (q, J=7.5 Hz, 2H), 3.05 (t, J=5.5 Hz, 2H), 3.73 (s, 3H), 3.86 (t, J=5.5 Hz, 2H), 7.75 (s, 2H), 7.80 (s, 1H).
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