[C:1]1([CH2:7][CH2:8][CH:9]([CH2:13][S:14][C:15](=[O:17])[CH3:16])[C:10]([OH:12])=O)[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.[NH2:18][C@H:19]([C:24]([O:26][C:27]([CH3:30])([CH3:29])[CH3:28])=[O:25])[CH2:20][CH:21]([CH3:23])[CH3:22].O.ON1C2C=CC=CC=2N=N1.CN1CCOCC1>C1COCC1.C(Cl)Cl>[C:27]([O:26][C:24](=[O:25])[C@H:19]([CH2:20][CH:21]([CH3:22])[CH3:23])[NH:18][C:10](=[O:12])[CH:9]([CH2:13][S:14][C:15](=[O:17])[CH3:16])[CH2:8][CH2:7][C:1]1[CH:2]=[CH:3][CH:4]=[CH:5][CH:6]=1)([CH3:30])([CH3:29])[CH3:28]To a solution of 4-phenyl-2-[acetylthio-methyl]butyric acid (3.57 g, 14.2 mmole) in 66 mL of THF at 0° C., was added (S)-leucine, t-butyl ester (2.91 g 15.6 mmole) and 1-hydroxybenzotriazole hydrate (HOBTH2O, 2.86 g, 21.2 mmole) and N-methylmorpholine (4.29 g, 42.4 mmole). The mixture was stirred at 0° C. for 15 minutes, then 5.42 g of 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide hydrochloride (EDC′HCl, 28.3 mmol) was added and the mixture stirred overnight. The solution was worked up by adding 100 mL methylene chloride and the mixture extracted with 3×50 mL of 5% sodium bicarbonate and washed with 2×50 mL of brine. The organic layer was dried over MgSO4, filtered, and the solvent removed under reduced pressure. The residue was purified by flash chromatography on silica gel eluted with methylene chloride/ethyl acetate (95/5). The product was separated as diastereomeric (R,S) and (S,S) fractions. The absolute stereochemistry of each fraction was not determined. Higher Rf material=1.78 g; lower Rf material=1.90 g.
Wird geladen…