2-Chlorotrityl chloride resin (1.07 mmol/g, 100-200 mesh, 1% DVB, manufactured by Chem-Impex, 3.00 g, 3.21 mmol) and dichloromethane (20 ml) were mixed, followed by shaking at room temperature. Dichloromethane was removed, after which methanol (0.52 ml, 12.85 mmol) and diisopropylethylamine (1.35 ml, 7.75 mmol) were added to a solution of (S)-6-(4-(2-((((9H-fluoren-9-yl)methoxy) carbonyl)amino)-3-oxo-3-(piperidin-1-yl)propyl)phenyl)hexanoic acid (Compound SP427) (0.91 g, 1.60 mmol) in dichloromethane (14 ml) and the resulting mixture was added to the resin, followed by shaking at room temperature for 5 minutes. The reaction solution was removed, after which methanol (4.2 ml) and diisopropylethylamine (1.4 ml) were added to dichloromethane (14 ml), and the resulting mixture was added, followed by shaking at room temperature for 2.5 hours. This reaction solution was removed, and dichloromethane (20 ml) was then placed, followed by shaking. Dichloromethane was removed, and dichloromethane (20 ml) was then placed again, followed by shaking. Dichloromethane was removed, and the resin was then dried under reduced pressure to afford the title compound (Compound SP428) (3.15 g).
