3-acetyl-4,5-dimethyl-2-pyrrole carboxylic acid 10b (2.5 g, 13.7 mmol) in DMF (56 mL) was treated with EDC (2.75 g, 14.4 mmol) and HOBt (2.20 g, 14.4 mmol) and stirred at RT for 15 minutes. Amine 16b (6.23 g, 13.0 mmol) in DMF (10 mL) was added, the reaction mixture stirred at RT and monitored by HPLC. The mixture was concentrated in vacuo, then dissolved in EtOAc. 1.0N glycine sodium salt aqueous solution was added until all excess amino ester 16b was consumed (several hours). The mixture was washed with 1N HCl (3×), brine, bicarb (3×), and brine, then dried over sodium sulfate, filtered, and concentrated in vacuo. Purification through a short plug of silica gel (25%EA/Hex) afforded 7.08 g, (85%) of 1-(2-{2-[(3-acetyl-4,5-dimethyl-1H-pyrrole-2-carbonyl)-amino]-2-cyclohexyl-acetylamino}-3,3-dimethyl-butyryl)-octahydro-indole-2-carboxylic acid tert-butyl ester 17b.
