Reaction Steps
To a solution of alcohol 19 (83.8 mg, 0.0712 mmol, 1.0 equiv) in CH2Cl2 (7.1 mL, 0.001M) in a 25 mL rb flask at 0° C. was added diisopropylethylamine (45.8 mg, 0.427 mmol, 6.0 equiv) and TBSOTf (47.0 mg, 0.178 mmol, 2.5 equiv) via syringe. The solution was stirred at 0° C. for 40 min, then quenched by the addition of 1.0 mL of methanol. Stirring was continued for another 10 min, and then saturated aqueous NaHCO3 solution (5 mL) was added. The aqueous phase was separated and extracted with CH2Cl2 (3×10 mL). The organic phases were combined, dried over Na2SO4 and concentrated under reduced pressure. Purification was accomplished by flash chromatography on a 4×10 cm column, eluting with 10% EtOAc/hexanes, collecting 18×150 mm test tube fractions. The product containing fractions (6-13) were combined and concentrated under reduced pressure to give the product 7 (89.3 mg, 98% yield) as a colorless oil. Rf=0.73 (20% EtOAc/Hexanes); [α]D20=+8.1 (c=0.40, CHCl3); 500 MHz 1H NMR (CDCl3) δ 7.70-7.66 (m, 4H), 7.44-7.35 (m, 11H), 7.20 (d, J=8.8 Hz, 2H), 6.86 (d, J=8.3 Hz, 2H), 6.02 (d, J=5.6 Hz, 1H), 5.47 (dd, J=16.1, 6.3 Hz, 1H), 4.78 (dd, J=10.3, 6.8 Hz, 2H), 4.65 (s, 1H), 4.63 (s, 2H), 4.56 (s, 1H), 4.46 (d, J=10.7 Hz, 1H), 4.38 (d, J=10.7 Hz, 1H), 4.14-4.04 (m, 2H), 3.95-3.88 (m, 1H), 3.85-3.71 (m, 8H), 3.60-3.50 (m, 2H), 3.50-3.44 (m, 1H), 3.29 (s, 3H), 2.43 (dd, J=8.3, 5.9 Hz, 2H), 2.29 (d, J=13.2 Hz, 1H), 2.17 (d, J=13.2 Hz, 1H), 2.04-1.90 (m, 6H), 1.86-1.72 (m, 5H), 1.68-1.48 (m, 5H), 1.16 (d, J=6.3 Hz, 3H), 1.12 (s, 3H), 1.09 (s, 3H), 1.06 (s, 9H), 0.89 (s, 9H), 0.88 (s, 9H), 0.09 (s, 3H), 0.08 (s, 3H), 0.07 (s, 3H), 0.06 (s, 3H); 125 MHz 13C NMR (CDCl3) δ 207.4, 159.3, 144.4, 138.1, 137.1, 135.8, 135.8, 134.1, 134.0, 131.3, 129.8, 129.8, 129.6, 129.4, 128.6, 128.0, 127.9, 127.9, 114.0, 109.0, 104.1, 93.4, 79.2, 75.3, 75.1, 72.9, 72.2, 72.0, 72.0, 70.8, 69.9, 69.6, 69.1, 60.6, 55.5, 52.8, 44.4, 42.8, 42.5, 42.5, 42.1, 41.2, 40.4, 38.2, 38.0, 37.7, 30.7, 27.2, 26.1, 23.3, 21.9, 19.4, 18.3, 18.3, 14.0, −3.9, −4.2, −4.3, −4.4; 125 MHz DEPT 13C NMR (CDCl3) CH3 δ 55.5, 52.8, 27.2, 26.1, 23.3, 21.9, 14.0, −3.9, −4.2, −4.3, −4.4; CH2 δ 109.0, 93.4, 72.2, 69.6, 60.6, 42.8, 42.5, 42.5, 42.1, 41.2, 40.4, 38.2, 38.0, 37.7, 30.7; CH δ 137.1, 135.8, 135.8, 129.8, 129.8, 129.6, 129.4, 128.6, 128.0, 127.9, 127.9, 114.0, 79.2, 75.3, 75.1, 72.9, 72.0, 72.0, 70.8, 69.9, 69.1, C δ 207.4, 159.3, 144.4, 138.1, 134.1, 134.0, 131.3, 104.1, 44.4, 19.4, 18.3, 18.3; IR (neat) 2930, 2856, 1728, 1513, 1465, 1382, 1250, 1110, 835, 775, 738, 703, 536 cm−1; HRMS (ESI/APCI) calcd for C75H114O12NaSi3 (M+Na) 1313.7516. found 1313.7560.
