C(N(CC)CC)C.[CH2:8]1[C@@H:13]([NH2:14])[C:11](=[O:12])[S:10][CH2:9]1.Cl.[CH:16](=O)[CH:17]([CH3:19])[CH3:18].[BH3-]C#N.[Na+]>CO>[CH2:16]([NH:14][CH:13]1[CH2:8][CH2:9][S:10][C:11]1=[O:12])[CH:17]([CH3:19])[CH3:18]4.6 mmol of triethylamine are added at 0° C., under an inert atmosphere, to a solution of 4.23 mmol of D-homocysteine thiolactone hydrochloride and 8.46 mmol of isobutyraldehyde in 20 ml of methanol. After stirring for 4 hours at ambient temperature, the reaction mixture is cooled to 0° C. and 8.8 mmol of NaCNBH3 are slowly added in the course of 40 minutes. After stirring for 30 minutes at 0° C., the reaction mixture is hydrolysed and then extracted with ether. The combined organic phases are then washed with a saturated NaCl solution, dried over sodium sulphate, filtered and concentrated under reduced pressure. Chromatography on silica gel (dichloromethane/methanol: 99/1) allows the expected product to be isolated in the form of syrup.
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