[NH2:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[CH2:8]([O:10][CH:11]([O:16][CH2:17][CH3:18])[CH2:12][N:13]=[C:14]=[NH:15])[CH3:9].CS(O)(=O)=O.[OH-].[Na+]>C(O)C>[CH2:17]([O:16][CH:11]([O:10][CH2:8][CH3:9])[CH2:12][NH:13][C:14]([NH:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1)=[NH:15])[CH3:18]Aniline (1.66 g, 17.8 mmol) was dissolved in ethanol (25 mL), and N-(2,2-diethoxyethyl)carbodiimide (a), (2.82 g, 17.8 mmol), was added dropwise. Then methanesulfonic acid (1.71 g, 17.8 mmol) was added, and the mixture was warmed at reflux for 24 h. The reaction mixture was poured into NaOH (0.5 M) and extracted with CH2Cl2. Drying and concentration afforded a product that was subjected to flash chromatography to give the intermediate guanidine (b) (3.3 g, 73.8%). NMR (500 MHz, DMSO-d6) δ 7.27-6.90 (m, 5H), 4.55 (t, 1H), 3.76-3.70 (m, 2H), 3.60-3.54 (m, 2H), 3.35-3.34 (d, 2H), 1.22 (pent, 6H). MS: 249.8 (M−H)−; 252.1 (M+H)+.
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