A solution of (3R,5R,6S)-tert-butyl 2-oxo-5,6-diphenyl-3-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)butyl)morpholine-4-carboxylate (5.00 g, 9.34 mmol) and TMEDA (10 mL, 65 mmol, 7 equiv) in THF (51 mL, 0.2 M) was cooled to −78° C. and treated with allyl iodide (17 mL, 187 mmol, 20 equiv) and potassium bis(trimethylsilyl)amide (47 mL, 0.9 M in THF, 46.7 mmol, 5 equiv) drop wise and stirred for 30 min. Once the addition was complete, the cooling bath was removed and the mixture was stirred over night. Once complete by TLC, the reaction mixture was quenched with 0.5N HCl (5-10 equiv), diluted with heptane and washed successively with water and saturated aqueous NaCl, dried over MgSO4, filtered and concentrated. Purification by MPLC (1-60% ethyl acetate in heptane over 6 CV) gave (3R,5R,6S)-tert-butyl 3-allyl-2-oxo-5,6-diphenyl-3-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)butyl)morpholine-4-carboxylate as colorless oil (5.2 g, 96%). Rf 0.55 (30% ethyl acetate in heptane); 1H NMR (CDCl3, 300 MHz) δ 7.39-7.14 (m, 10H), 7.10 (dd, J1=5.4 Hz, J2=1.8 Hz, 1H), 6.08 (d, J=5.4 Hz, 1H), 5.95-5.80 (m, 1H), 5.27-5.17 (m, 2H), 3.30-3.15 (m, 1H), 2.89-2.76 (m, 1H), 2.20-2.07 (m, 2H), 1.54 (s, 9H), 1.35-1.21 (m, 4H), 1.78 (s, 12H), 0.46 (t, J=8.4 Hz, 2H); ESI-LCMS m/z calcd for C34H46BNO6: expected 575.3. found 574.3 (M+H)+.
