Reaction Steps
Powered CeCl3.7H2O (757.0 mg, 2.03 mmol, 10.0 equiv) was placed in a 10 mL rb flask and heated to 170° C. under vacuum. After 16 h at 170° C., the dried CeCl3 was cooled to rt, and the flask was purged with N2. THF (2.5 mL) was added, and the mixture was stirred at rt for 2 h. Meanwhile, a 25 mL three-necked rb flask equipped with condenser and magnetic stir bar was charged with magnesium turnings (124.0 mg, 5 mmol, 1.0 equiv), and a crystal of iodine. The flask was heated with a heat gun for 5 min while stirring. THF (5.0 mL) was added into the reaction via syringe, and the reaction mixture was heated with the heat gun to reflux. TMSCH2Cl (0.613 g, 5.0 mmol, 1.0 equiv) was then added to the reaction dropwise via syringe. The reaction was stirred at rt for 1.5 h to give an assumed 1.0 M solution of TMSCH2MgCl. The CeCl3/THF mixture was cooled to −78° C., then a solution of TMSCH2MgCl (2.03 mL, 2.03 mmol, 10.0 equiv) was added to the reaction dropwise via syringe. After 1 h at −78° C., ester 18 (167.2 mg, 0.203 mmol, 1.0 equiv) in THF (1.0 mL) was added to the reaction via cannula. An additional THF (0.6 mL) rinse was used to transfer the remaining ester residue into the reaction mixture. The solution was allowed to warm to rt and stirred overnight. The mixture was then cooled to −78° C., and then a 1N aqueous HCl solution (4.0 mL) was added to the mixture dropwise via syringe. The reaction mixture was then allowed to warm to rt and the phases were separated. The aqueous phase was extracted with Et2O (3×10 mL). The organic phases were combined, washed with saturated aqueous NaHCO3 solution (10 mL), dried over Na2SO4, and concentrated under reduced pressure. Purification was accomplished by flash chromatography on a 3×12 cm column, eluting with 50% EtOAc/hexanes, collecting 18×150 mm test tube fractions. The product containing fractions (19-22) were combined and concentrated under reduced pressure to give the product 5 (103.4 mg, 71% yield) as a colorless oil: Rf=0.31 (50% EtOAc/Hexanes); [α]D20=+15.8 (c=1.04, CHCl3); 500 MHz 1H NMR (CDCl3) δ 7.69 (dd, J=11.4, 1.7 Hz, 2H), 7.68 (dd, J=4.4, 1.3 Hz, 2H), 7.46-7.38 (m, 6H), 7.21 (d, J=8.4 Hz, 2H), 6.86 (d, J=8.6 Hz, 2H), 4.67 (dd, J=14.1, 2.0 Hz, 2H), 4.46 (d, J=11.1 Hz, 1H), 4.37 (d, J=11.1 Hz, 1H), 4.00-3.94 (m, 1H), 3.81-3.74 (m, 6H), 3.60-3.50 (m, 2H), 3.44 (bs, 1H), 2.22 (dd, J=13.8, 7.1 Hz, 1H), 2.07 (dd, J=13.8, 6.0 Hz, 1H), 1.96 (ddd, J=12.1, 2.4, 2.0 Hz, 1H), 1.87 (ddd, J=12.4, 2.4, 2.4 Hz, 1H), 1.84-1.78 (m, 3H), 1.72-1.60 (m, 5H), 1.57 (s, 2H), 1.07 (s, 9H), 0.05 (s, 9H); 125 MHZ 13C NMR (CDCl3) δ 159.3, 144.6, 135.8, 134.0, 134.0, 131.1, 129.8, 129.7, 127.8, 127.8 114.0, 110.1, 76.3, 72.8, 72.5, 71.6, 69.5, 67.8, 60.5, 55.4, 46.6, 42.4, 41.8, 41.6, 41.5, 37.5, 27.1, 27.1, 19.3, −1.2; 125 MHz DEPT 13C NMR (CDCl3) CH3 δ 55.4, 27.1, −1.2; CH2 δ 101.1, 71.6, 60.5, 46.6, 42.4, 41.8, 41.6, 41.5, 37.5, 27.1; CH δ 135.8, 129.8, 129.7, 127.8, 127.8, 114.0, 76.3, 72.8, 72.5, 69.5, 67.8 C δ 159.3, 144.6, 134.0, 134.0, 131.1, 19.3; IR (neat) 3441, 2941, 1612, 1513, 1427, 1248, 1111, 1037, 848, 738, 702, 614, 541, 505 cm−1; HRMS (ESI/APCI) calcd for C42H62O6NaSi2 (M+Na) 741.3977. found 741.3979.
