Reaction Steps
A DCM (2 mL) solution of 15 (29 mg, 6.6 μmol, 1 equiv.) was cooled to −78° C. in a 10-mL teardrop-shaped flask, and a DCM solution of bromodimethylborane (2.65 M, 0.25 mL, 0.66 mmol, 10 equiv.) was added dropwise. After stirring the bright yellow solution at −78° C. for 10 min, it was quenched sequentially at −78° C. with 1.25 mL NEt3 and saturated aqueous NaHCO3. The mixture was warmed to room temperature and extracted thrice with EtOAc. The organic extracts were combined, washed with brine, dried over Na2SO4, filtered, and concentrated in vacuo to yield a yellow residue. Flash column chromatography (30 mL SiO2, 9:1 hexane:EtOAc) afforded 26.7 mg (58 μmol, 88% yield) of 17 as a yellow oil. TLC Rf 0.38 (7:3 hexane:EtOAc). 1H NMR (600 MHz; C6D6): δ 5.55 (dq, J=11.5, 1.3 Hz, 1H), 5.35 (t, J=7.3 Hz, 1H), 5.28 (t, J=6.6 Hz, 1H), 3.71 (s, 1H), 3.67 (dd, J=11.8, 5.3 Hz, 1H), 3.53 (s, 3H), 3.34 (dd, J=15.2, 6.4 Hz, 1H), 3.16 (m, 1H), 3.14 (s, 1H), 3.06 (s, 3H), 2.92 (dd, J=14.1, 11.5 Hz, 1H), 2.86 (tdd, J=12.8, 7.7, 5.0 Hz, 1H), 2.26 (d, J=14.1 Hz, 1H), 2.08 (tt, J=12.5, 6.1 Hz, 1H), 2.00 (dd, J=12.8, 12.0 Hz, 1H), 1.84 (s, 3H), 1.72 (s, 3H), 1.72-1.68 (m, 1H), 1.62 (s, 6H), 1.60-1.58 (m, 1H), 1.56 (s, 3H), 1.42 (s, 3H), 1.27 (td, J=12.7, 4.4 Hz, 1H), 1.12 (s, 3H). 13C NMR (126 MHz; C6D6): δ 197.3, 171.2, 136.5, 131.8, 131.1, 125.8, 124.5, 123.36, 123.23, 100.2, 73.4, 61.8, 57.5, 52.4, 48.2, 40.9, 39.7, 37.5, 30.8, 26.0, 25.76, 25.72, 23.7, 22.2, 18.01, 17.90, 17.7, 17.3. FTIR (thin film) νmax: 3464 (br), 2969, 2928, 2859, 1665, 1615, 1450, 1376, 1329, 1235, 1087, 1040, 986, 928, 907, 858, 737 cm-1. HRMS-ESI (m/z): [M+H]+ calculated for C28H44O5, 461.3262. found, 461.3254.
