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Example C: Synthesis of 3-(3-(2,5-dioxo-4-(3,4,5-trimethoxyphenyl)-2,5-dihydro-1H-pyrrol-3-yl)-1H-indol-1-yl)-2-amino-4-methylpentanoic acid propyl ester of 3-bromopropoxy-tert-butyl dimethylsilane. (3-Bromopropoxy)tert-butyldimethylsilane was prepared using the method modified by Galka et al. (J. Lab. Comp. Rad. 2005, 48(11): 797-809). The procedure was as follows: a mixture of 3-bromo-1-propanol (39.1 mmol, 5.43 g), tert-butyldimethylchlorosilane (43.2 mmol, 6.47 g) and imidazole (46.7 mmol, 3.20 g) was stirred and reacted for 3 h at room temperature under inert gas protection. After completion of the reaction, the reaction was quenched with water and the reaction mixture was extracted with diethyl ether. The organic layers were combined, dried with anhydrous magnesium sulfate, filtered and concentrated. Purification by column chromatography (with petroleum ether as eluent) afforded the target product (3-bromopropoxy)tert-butyldimethylsilane (36.4 mmol, 93% yield). The product was characterized by 1H NMR (300 MHz, CDCl3): δ 3.73 (t, 3J = 5.7 Hz, 2H, CH2O), 3.51 (t, 3J = 6.4 Hz, 2H, CH2Br), 2.02 (q, 3J = 5.7 Hz, 3J = 6.4 Hz, 2H, CH2CH2CH2), 0.89 (s, 9H, C( CH3)3), 0.06 (s, 6H, 2×CH3).