To a solution of di-tert-butyl (4S)-4-(3-hydroxypropyl)-N-trityl-L-glutamate (203.4 mg, 0.36 mmol) and triethylamine (150 μL, 1.09 mmol) in dichloromethane (5.0 mL) was added quinoline-8-sulfonyl chloride (124.1 mg, 0.55 mmol) at 0° C. The reaction mixture was stirred at 0° C. for 3 h and at room temperature for overnight and then water was added. The organic layer was separated, and aqueous layer was extracted with dichloromethane. Combined organic solution was dried over sodium sulfate, and concentrated in vacuo. The residue was purified by flash column chromatography (MeOH/CH2Cl2=1/99) to give the desired product (140 mg, 51%) as a white solid.
