[CH3:1][C:2]([NH:5][S:6]([C:9]1[S:17][C:16]2[S:15](=[O:19])(=[O:18])[NH:14][CH2:13][C:12](=[O:20])[C:11]=2[CH:10]=1)(=[O:8])=[O:7])([CH3:4])[CH3:3].C(OCC)C.N(CCO)CCO>C1COCC1>[CH3:4][C:2]([NH:5][S:6]([C:9]1[S:17][C:16]2[S:15](=[O:19])(=[O:18])[NH:14][CH2:13][C@@H:12]([OH:20])[C:11]=2[CH:10]=1)(=[O:8])=[O:7])([CH3:1])[CH3:3]A solution of (+)-diisopinocamphenylchloroborane (3.8 g, 11.8 mmol) was dissolved in anhydrous THF (10 mL) under nitrogen and cooled to -35° C.; the product from Step A (0.8 g, 2.36 mmol) was added and this mixture was stirred at -35° C. for 24 hr. The solvent was evaporated and the residue was mixed with diethyl ether (15 mL) and diethanol amine (0.62 g, 5.9 mmol) was added followed by stirring for 2 h, filtration, and evaporation. The residue was purified by column chromatography (silica, hexane then hexane/ethyl acetate gradient) to give a colorless solid (0.60 g, 75%): mp 57°-58° C. The optical purity was established to be >90% ee by HPLC analysis of the diastereomeric esters formed with (S)-α-methoxyphenylacetic acid.
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