Reaction Steps
Triethylsilane (2.25 mL, 14.1 mmol) was added to a stirring, room temperature solution of 63 (1.5291 g, 4.55 mmol) in trifluoroacetic acid (TFA) (10.8 mL, 0.42 M) under N2. After stirring at room temperature for 3 hours, the reaction was heated to 35° C. for 35 min, then the TFA was removed under vacuum, and the crude product was taken up in EtOAc, washed with brine, dried with Na2SO4, filtered, concentrated, and purified by preparative reverse phase HPLC with the following conditions: 0 to 12 min, 35:65 H2O:CH3CN; 14-15 min, 35:65 to 0: 100 H2O:CH3CN; 20 mL/min.; λ=254 nM; 3.67 g/mL, 0.2 mL/ injection. 0.8402 g (57.3%) of 64 was obtained as a fluffy white solid. (Note: An undesired impurity has a retention time of 12.281 min by HPLC.) 1H (CDCl3, 400 MHz): δ 9.07 (1H, broad s), 7.55 (1H, dd, J=8.0, 1.3 Hz), 7.21 (1H, td, J=7.3, 1.3 Hz), 7.17 (1H, dd, J=7.6, 2.4 Hz), 7.06 (1H, ddd, J=7.9, 7.0, 2.3 Hz), 6.82 (1H, s), 6.72 (1H, s), 4.32 (2H, t, J=7.2 Hz), 2.99 (2H, t, J=8.0 Hz), 2.78 (2H, t, J=7.9Hz), 1.36 (3H, t, J=7.2 Hz) ppm. 13C (CDCl3, 100 MHz): δ 161.21, 141.03, 132.75, 130.41, 127.63, 127.32, 125.31, 124.43, 122.66, 120.68, 114.83, 60.22, 37.78, 27.03, 14.48 ppm. DEPT (CDCl3, 100 MHz): CH3 carbons: 14.48; CH2 carbons: 60.22, 37.78, 27.03; CH carbons: 132.75, 130.41, 127.63, 127.32, 120.68, 114.83 ppm. HPLC: 11.355 min.
