Reaction Steps
Alcohol 5b (219 mg, 0.610 mmol) was dissolved in 4 mL of methylene chloride (DCM). To this mixture was added pyridine (0.074 mL, 0.92 mmol) and dimethylaminopyridine (DMAP) (7.4 mg, 0.061 mmol), and the mixture was taken to 0° C. To this mixture was added (R)-(−)-MTPA-Cl (170 mg, 0.671 mmol), and the mixture was allowed to warm to room temperature overnight. The reaction was quenched with saturated aqueous NH4Cl (50 mL), and the aqueous layer was extracted 3 times with methylene chloride (3×50 mL). The organic extracts were combined and dried with MgSO4 and concentrated. A 1H NMR (400 MHz) spectrum of the crude mixture showed the absence of diastereomers, meaning that alcohol 5b was enantiomerically pure after crystallization. The product mixture was then purified using flash chromatography (hexanes:ethyl acetate 12:1) to give 10b quantitatively. 1H NMR (400 MHz, CDCl3) δ 7.54 (m, 2H), 7.41 (m, 3H), 6.40 (d, J=1.8 Hz, 1H), 6.26 (d, J=1.9 Hz, 1H), 4.72 (dd, J=12, 4.9 Hz, 1H), 3.77 (s, 3H), 3.75 (s, 3H), 3.54 (s, 3H), 2.62 (m, 1H), 2.51 (dd, J=14, 6.2 Hz, 1H), 2.46 (dd, J=8.4, 2.9 Hz, 1H), 1.85-1.76 (m, 1H), 1.74-1.67 (m, 3H), 1.65-1.57 (m, 3H), 1.23 (td, J=13, 4.2 Hz, 1H), 1.07 (s, 3H), 1.04 (s, 3H), 1.04 (m, 1H), 0.92 (s, 3H), 0.87 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 166.3, 159.5, 155.8, 144.7, 133.2, 132.3, 129.5, 128.3 (2C), 127.6 (2C), 124.9, 122.0, 101.9, 96.9, 84.5, 64.2, 56.2, 55.4, 55.3, 55.1, 46.1, 38.1, 38.0, 37.9, 36.5, 29.5, 28.1, 23.0, 20.3, 19.0, 16.2, 16.1. ESIMS [M+Na]+ calcd for C33H41O5F3Na 597.2804, found 597.2814. [α]24D=−31.76°.
