Reaction Steps
A solution containing 11 (27.5 g, 30 mmol) in DCM (200 mL) was cooled to 0° C. TFA (50 mL) was added and the reaction was monitored by LC/MS analysis until complete conversion of 11 to 12 (ca. 3 h). The solvent was removed in vacuo and the dark, green-colored residue was dissolved in EtOAc (ca. 1 L). The EtOAc solution was carefully poured into a saturated aqueous NaHCO3/ice/water mixture to neutralize the residual TFA. The organic phase was separated and washed twice with saturated aqueous NaHCO3 then once with brine. The combined aqueous washes were back-extracted with EtOAc (2×100 mL) and the combined organic extracts were dried over anhydrous Na2SO4, filtered, and concentrated to afford 22 g of crude 12 as an off-white solid. 1H NMR (300 MHz, CDCl3+d4-MeOH), mixture of rotomers: δ11.62 (br s, 2H), 7.48-7.62 (m, 4H), 6.89 (ddd, J=2.4, 9.3, 9.3 Hz, 2H), 5.48 (dd, J=4.5, 4.8 Hz, 2H), 4.52 (dd, J=9.3, 9.3 Hz, 2H), 4.06 (dd, J=4.8, 12.3 Hz, 2H), 3.78 (d, J=12.3 Hz, 2H), 3.54-3.70 (m, 4H), 3.30-3.40 (m, 2H), 2.33 (s, 6H), 2.02-2.16 (m, 2H), 1.70-1.96 (m, 4H), 1.09 (t, J=7.2 Hz, 6H) ppm; 13C NMR (75 MHz, CDCl3+d4-MeOH): 8173.5, 170.9, 161.8, 158.6, 137.2, 137.1, 128.2, 128.1, 125.6, 118.7, 118.6, 108.6, 108.3, 108.0, 98.6, 98.1, 74.6, 60.1, 53.5, 33.5, 28.0, 21.4, 9.7 ppm. Mass spectrum (ESI), m/z 721.4 [(M)+; calcd for C38H46F2N6O6: 720.8].
