Cl.[NH2:2][CH2:3][CH:4]([CH2:16][CH:17]([CH3:19])[CH3:18])[CH2:5][C:6]([O:8][CH2:9][C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1)=[O:7].CN1CCOCC1.Cl[C:28]([O:30][CH:31]([Cl:35])[CH:32]([CH3:34])[CH3:33])=[O:29]>ClCCl>[Cl:35][CH:31]([O:30][C:28]([NH:2][CH2:3][CH:4]([CH2:16][CH:17]([CH3:19])[CH3:18])[CH2:5][C:6]([O:8][CH2:9][C:10]1[CH:11]=[CH:12][CH:13]=[CH:14][CH:15]=1)=[O:7])=[O:29])[CH:32]([CH3:34])[CH3:33]To a stirred solution of (39) (594 mg, 2.38 mmol) in dichloromethane at 0° C. was added N-methylmorpholine (0.523 mL, 4.77 mmol) and 1-chloro-2-methylpropyl chloroformate (0.347 mL, 2.38 mmol). The resulting solution was stirred at 0° C. until the reaction was complete (˜30 min, as monitored by TLC) and then was diluted with dichloromethane, washed successively with cold 1N HCl solution, water and brine, then dried over anhydrous Na2SO4. Filtration and removal of the solvent in vacuo afforded the title compound (42) as a mixture of two diastereomers (840 mg, 92%), which was used without further purification in the following example. 1H-NMR (CDCl3, 400 MHz): δ 0.86 (2 d, 6H), 1.02 (2 d, 6H), 1.15 (m, 2H), 1.63 (m, 1H), 2.14 (m, 2H), 2.34 (m, 2H), 3.10 (m, 1H), 3.28 (m, 1H), 5.11 (br.s, 3H), 6.29 (d, 1H), 7.31 (m, 5H).
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