Reaction Steps
In a manner similar to the synthesis of 116, compound 115 (960 mg, 3.2 mmol) was hydrolyzed with LiOH.H2O (202 mg, 4.8 mmol), recrystallized by refluxing with DCHA (0.76 mL, 3.84 mmol) and protected by reacting with 2,4′-dibromoacetophenone (979 mg, 3.52 mmol) to afford 118 as an amorphous solid (1.39 g, 90%). Rf=0.35 (DCM); [α]25D=−1.2° (c=1.0, CHCl3); NMR (300 MHz, CDCl3): δ 7.74 (d, 2H, J=8.4 Hz, aromatic), 7.60 (d, 2H, J=8.4 Hz, aromatic), 5.39 (d, 1H, J=16.5 Hz, CH′2a), 5.29 (d, 1H, J=16.5 Hz, CH′2b), 4.08 (m, 1H, H-3), 2.65 (dd, 1H, J2a,2b=15.0 Hz, J2a,3=3.0 Hz, H-2a), 2.54 (dd, 1H, J2a,2b=15.0 Hz, J2b,3=9.0 Hz, H-2b), 1.58-1.46 (m, 3H, H-4, H-15), 1.24-1.13 [m, 20H, H-(5-14)], 0.83 (d, 6H, J15,16=6.6 Hz, H-14). 13C NMR (75 MHz, CDCl3): δ 191.60 (C═O), 171.86 (C═O), 132.49-129.24 (m, aromatic), 68.38 (C-3), 65.74 (C-2′), 41.96 (C-2), 39.00 (C-14), 36.54 (C-4), 22.61 (C-16). HR MS (m/z) calculated for C25H39BrO4 [M+Na]+, 505.1924; found, 505.1160.
