C([BH-](CC)CC)C.[Li+].[Br:9][C:10]1[CH:15]=[CH:14][C:13]([C@@H:16]([N:18]2[CH2:23][CH2:22][C@:21]([CH2:30][C:31]3([CH3:34])[CH2:33][O:32]3)([C:24]3[CH:29]=[CH:28][CH:27]=[CH:26][CH:25]=3)[O:20][C:19]2=[O:35])[CH3:17])=[C:12]([CH3:36])[CH:11]=1>O1CCCC1>[Br:9][C:10]1[CH:15]=[CH:14][C:13]([C@@H:16]([N:18]2[CH2:23][CH2:22][C@:21]([CH2:30][C:31]([OH:32])([CH3:34])[CH3:33])([C:24]3[CH:25]=[CH:26][CH:27]=[CH:28][CH:29]=3)[O:20][C:19]2=[O:35])[CH3:17])=[C:12]([CH3:36])[CH:11]=1Lithium triethylborohydride (1 mol/L in tetrahydrofuran, 4.2 mL) was added to an ice-cold solution of 3-[(S)-1-(4-bromo-2-methyl-phenyl)-ethyl]-(S)-6-(2-methyl-oxiranylmethyl) -6-phenyl-[1,3]oxazinan-2-one (1.55 g, ca. 85-90% pure) in tetrahydrofuran (15 mL) at such a rate that the solution temperature remained below 10° C. The resulting solution was stirred in the cooling bath for one more hour and at room temperature for another 2 h. Then, the solution was cooled in an ice bath and the reaction was quenched by the careful addition of water (7 mL). After the addition of aqueous hydrochloric acid and ethyl acetate (80 ml), the organic phase was separated, washed with brine, and dried (MgSO4). The solvent was evaporated to afford the title compound. Yield: 1.48 g (95% of theory); LC-MS (Method 4): tR=4.00 min; Mass spectrum (ESI+): m/z=446/448 (Br) [M+H]+.
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