Trichloro(dimethylsulfonio)boranuide → (S)-4-Benzyl-3-((S)-3-(4-hydroxyphenyl)-3-(isoxazol-3-yl)propanoyl)oxazolidin-2-one

Boron trichloride methyl sulfide complex (51 mL, 2.0 M solution in DCM) was added to 7.4 (8.2 g, 17 mmol) in DCM (100 mL) at 0° C. After addition, the ice bath was removed, and the mixture was stirred at room temperature for 7 hours. The mixture was cooled in an ice bath and quenched by adding saturated sodium bicarbonate until the mixture was neutralized. More DCM (400 mL) was added, and the organic layer was separated, washed with brine, dried, and concentrated under vacuum. The crude product (6.5 g) was dissolved in 50 mL of hot MeOH. After cooling, the crystallized product was collected by filtration and washed once with MeOH to give 7.5 (4.2 g). The filtrate was concentrated, and the solid that formed was collected and washed to give an additional 1.2 g of compound 7.5. MS ESI (pos.) m/e: 393 (M+H). 1H NMR (CDCl3) δ 8.29 (d, 1H), 7.30 (m, 3H), 7.20 (d, 2H), 7.15 (d, 2H), 6.95 (d, 2H), 6.14 (d, 1H), 4.71 (dd, 1H), 4.63 (m, 1H), 4.16 (d, 2H), 4.00 (dd, 1H), 3.54 (dd, 1H), 3.21 (dd, 1H), 2.76 (dd, 1H).