Reaction Steps
Compound 61a (26.0 g, 46.18 mmol) was treated with NaOMe/MeOH (25 wt. %, 2.7 mL) in MeOH (200 mL) at room temperature. After 6 h, the mixture was neutralized (IRC-50 resin, weak acid) and concentrated to give product 61b (20.0 g, 99%) as semisolids: 1H-NMR (500 MHz, CDCl3), δ 7.78-7.82 (m, 2H), 7.68-7.72 (m, 2H), 5.16 (d, J=8.5 Hz, 1H), 4.63 (d, J=4.5 Hz, 1H), 4.25-4.31 (m, 2H), 4.06 (dt, J=2.0, 8.5 Hz, 1H), 3.88-3.89 (m, 2H), 3.76 (dt, J=10.0, 6.5 Hz, 1H), 3.65-3.71 (m, 1H), 3.59 (s, 3H), 3.48 (t, J=6.5 Hz, 1H), 3.43 (dt, J=9.5, 3.5 Hz, 1H), 3.38 (dt, J=10.0, 6.5 Hz, 1H), 1.90-2.02 (m, 2H), 1.31-1.43 (m, 4H), 1.00-1.09 (m, 2H); 13CNMR (125 MHz, CDCl3), δ 174.0, 168.4, 134.0, 131.6, 123.4, 98.31, 75.53, 71.53, 71.20, 69.43, 61.63, 56.66, 51.38, 33.65, 28.84, 25.18, 24.34; HRMS (M+Na) calcd for C21H27O9NNa 460.1584, found 460.1598.
