[Br:1][C:2]1[CH:18]=[CH:17][C:5]([CH2:6][NH:7][C:8](=[NH:16])[CH:9](OCC)OCC)=[CH:4][CH:3]=1.[OH-].[Na+]>S(=O)(=O)(O)O>[Br:1][C:2]1[CH:18]=[C:17]2[C:5](=[CH:4][CH:3]=1)[CH:6]=[N:7][C:8]([NH2:16])=[CH:9]2N-(4-bromobenzyl)-2,2-diethoxyacetimidamide (1.53 g, 4.85 mmol) in sulfuric acid (4 mL, 95-98%) was heated at 40 C for 14 h. The mixture was neutralized with 1 M NaOH to pH 7 and the resulting suspension was filtered. The residue was purified by silica gel chromatography with 20-55% ethyl acetate in hexanes. The desired fractions were concentrated to give a brownish yellow solid (0.434 g, 40%). LCMS: R.T.=1.62; [M+2]+=225.1.
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