(3S,7S)-3-[4-(3,4-Dichloro-benzyloxy)-phenyl]-1-methyl-2-oxo-2,3,5,6,7,8-hexahydro-1H-4-oxa-1,6-diaza-anthracene-7-carboxylic acid (1R,2S,5R)-2-isopropyl-5-methyl-cyclohexyl ester (3.5 g, 5.37 mmol) was dissolved in 10 mL DMF and sodium bicarbonate (21.5 mmol) and (1-Bromo-propyl)-benzene (10.7 mmol) added. The mixture was stirred at 50° C. for 20 h and room temperature for 48 hours. The mixture was poured onto diethyl ether and 10% sodium carbonate. The aqueous layer was extracted with ether and organic layers combined. The organic layer was dried over sodium sulfate and concentrated. The residue was purified over silica (EtOAc-hexanes-DCM-TEA, 0.5/5/4.5/0.02) to provide (3S,7S)-3-[4-(3,4-Dichloro-benzyloxy)-phenyl]-1-methyl-2-oxo-6-((S)-1-phenyl-propyl)-2,3,5,6,7,8-hexahydro-1H-4-oxa-1,6-diaza-anthracene-7-carboxylic acid (1R,2S,5R)-2-isopropyl-5-methyl-cyclohexyl ester (803 mg, 1H NMR (400 MHz, d6 acetone): 7.7 (d, 1H), 7.6 (d, 1H), 7.46 (d, 1H), 7.33 (m, 7H), 6.98 (m, 2H), 6.87 (s, 1H), 6.77 (s, 1H), 5.65 (s, 1H), 5.13 (s, 2H), 4.55 (m, 1H), 4.20 (s, 2H), 3.9 (m, 1H), 3.55 (m, 1H), 3.38 (s, 3H), 2.95 (m, 2H), 1.6 (m, 6H), 1.15 (m, 1H), 0.95 (m, 1H) 0.9 (m, 2H), 0.8 (m, 4H), 0.7 (d, 3H), 0.65 (m, 6H).
