[C:1]([N:8]1[CH2:16][C:15]2[C:10](=[CH:11][CH:12]=[CH:13][CH:14]=2)[CH:9]1[C:17]([OH:19])=[O:18])([O:3][C:4]([CH3:7])([CH3:6])[CH3:5])=[O:2].[CH3:20][Si](C=[N+]=[N-])(C)C>C(Cl)Cl.CO>[C:1]([N:8]1[CH2:16][C:15]2[C:10](=[CH:11][CH:12]=[CH:13][CH:14]=2)[CH:9]1[C:17]([O:19][CH3:20])=[O:18])([O:3][C:4]([CH3:7])([CH3:6])[CH3:5])=[O:2]To a solution of N-BOC-1,3-dihydro-2H-isoindol-1-carboxylic acid (SNPE, 10 g, 38 mmol) in CH2Cl2 (100 mL) and MeOH (100 mL) at 0° C. was added trimethylsilyldiazomethane dropwise until the yellow color persisted. After stirring at rt for 15 min, the reaction mixture was concentrated in vacuo. The residue was azeotroped with toluene to afford N-BOC-1,3-dihydro-2H-isoindol-1-carboxylic acid, methyl ester which was used without further purification.
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