[C:1]([O:5][C:6](=[O:27])[NH:7][C@H:8]([C:16](=O)[NH:17][C:18]1[CH:23]=[CH:22][C:21]([I:24])=[CH:20][C:19]=1[NH2:25])[CH2:9][C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1)([CH3:4])([CH3:3])[CH3:2].C(OC(=O)N[C@H](C(=O)NC1C=C(I)C=CC=1N)CC1C=CC=CC=1)(C)(C)C>C(O)(=O)C>[C:1]([O:5][C:6](=[O:27])[NH:7][C@H:8]([C:16]1[NH:17][C:18]2[CH:23]=[CH:22][C:21]([I:24])=[CH:20][C:19]=2[N:25]=1)[CH2:9][C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1)([CH3:4])([CH3:3])[CH3:2]The mixture of regioisomers from step 2 {[(S)-1-(2-amino-4-iodo-phenylcarbamoyl)-2-phenyl-ethyl]-carbamic acid tert-butyl ester and [(S)-1-(2-amino-5-iodo-phenylcarbamoyl)-2-phenyl-ethyl]-carbamic acid tert-butyl ester} (1.0 g, 2.08 mmol) were dissolved in glacial acetic acid (30 mL) and heated to 65° C. for 1 hour. The reaction was cooled, concentrated in vacuo, basified with 10% w/v aqueous sodium hydrogen carbonate solution and extracted with ethyl acetate (2×20 mL). The organic extracts were combined, washed with brine, dried over sodium sulfate, filtered and concentrated in vacuo. The crude product was purified by chromatography over silica gel eluted with 20% v/v ethyl acetate/hexanes to give [(S)-1-(5-iodo-1H-benzoimidazol-2-yl)-2-phenyl-ethyl]-carbamic acid tert-butyl ester as a mixture of tautomers (950 mg, 99%).
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