[Br:1][C:2]1[CH:3]=[C:4]([CH:13]=[CH:14][CH:15]=1)/[CH:5]=[N:6]/[S@@:7]([C:9]([CH3:12])([CH3:11])[CH3:10])=[O:8].[Li][C:17]1[CH:18]=[CH:19][CH:20]=[CH:21][CH:22]=1>C1COCC1>[Br:1][C:2]1[CH:3]=[C:4]([C@@H:5]([C:17]2[CH:18]=[CH:19][CH:20]=[CH:21][CH:22]=2)[NH:6][S@@:7]([C:9]([CH3:11])([CH3:12])[CH3:10])=[O:8])[CH:13]=[CH:14][CH:15]=1(R,E)-N-(3-bromobenzylidene)-2-methylpropane-2-sulfinamide, 24-b, (12 g, 41.64 mmol) was dissolved in anhydrous THF (120 ml). The mixture was then cooled to −78° C. and PhLi (41 ml, 83.28 mmol) was added dropwise. After addition the mixture was allowed to stir at −78° C. for additional 2 h and warmed to room temperature for another 2 h. The mixture was quenched with saturated NH4Cl followed by extraction with ethyl acetate. The organic layer was dried over sodium sulfate and concentrated under vacuum. The residue was purified by column chromatography (petroleum ether/ethyl acetate=5/1) to provide the product, 24-c, (11.8 g, 77%). HPLC indicated that the diastereomer ratio is 90:10 and the product was used for the next step directly.
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