A 150 mL cylidrical glass vessel equipped with a coarse glass frit was charged with N-[(9H-fluoren-9-ylmethoxy)carbonyl]-3-[(2-propenyloxy)carbonyl]amino-L-alanine resin (Example 64; 5 g) and 25% piperidine in N-methylpyrrolidinone (50 mL). The mixture was agitated at room temperature for 30 min. The resin was filtered and treated again with fresh 25% piperidine in N-methylpyrrolidinone (50 mL) at room temperature for 30 min. After filtration, the resin was washed with dichloromethane and methanol. To the resin was added a solution prepared from 2-chloro-4-[[[(3-hydroxyphenyl)methyl]amino]carbonyl]benzoic acid (Example 26; 2.5 g, 8.2 mmol), HOAT (3.7 g, 27.2 mmol) and DICI (4.3 mL, 27.5 mmol) in N-methylpyrrolidinone (50 mL). The reaction mixture was agitated at room temperature for 1 h, and then filtered. The resin was washed with dichloromethane and methanol, and dried under vacuum to afford resin-bound N-[2-chloro-4-[[[(3-hydroxyphenyl)methyl]amino]carbonyl]benzoyl]-3-[(2-propenyloxy)carbonyl]amino-L-alanine.
