Reaction Steps
DIBAL-H (1.0 M in hexane, 11.7 mL, 11.7 mmol) was added dropwise to a stirred solution of TBS protected acetal 42 (1.53 g, 1.17 mmol) in anhydrous CH2Cl2 (2.3 mL) under an atmosphere of N2 at 0° C. After stirring for additional 30 min at 0° C. the reaction mixture was quenched by the careful addition of aqueous saturated aqueous potassium sodium tartrate (30 mL). The resulting mixture was stirred for 3 h at room temperature. The organic layer was separated, and the aqueous layer was extracted by CH2Cl2 (20 mL). The combined organic layers were washed with brine and dried over MgSO4 followed by the evaporation of the organic solution under reduced pressure. The residue was purified by column chromatography (EtOAc/hexane 1:9) to obtain pure 43 (1.35 g, 88%) as a colorless oil: IR (CHCl3) 3464, 2956, 2929, 2856, 1613, 1514, 1471, 1252, 1087, 836, 773 cm−1; 1H NMR (300 MHz, CDCl3) δ 7.46 (m, 6H), 7.28 (m, 1H), 6.88 (m, 2H), 5.61 (m, 2H), 5.39 (m, 1H), 5.28 (m, 1H), 4.57 (m, 1H), 4.53 (s, 2H), 3.92 (m, 2H), 3.83 (m, 1H), 3.80 (s, 3H), 3.60 (m, 2H), 3.56 (m, 2H), 3.46 (dd, J=6.2, 4.5 Hz, 1H), 3.37 (m, 1H), 3.03 (m, 1H), 2.86 (m 1H), 2.59 (m, 1H), 2.41 (m, 1H), 1.93 (m, 1H), 1.88 (m, 1H), 1.66 (m, 3H), 1.35 (m, 5H), 1.11 (d, J=7.0 Hz, 3H), 1.01 (d, J=6.8 Hz, 3H), 0.97 (d, J=6.8 Hz, 3H), 0.92 (m, 27H), 0.85 (m, 10H), 0.81 (s, 9H), 0.11 (s, 3H), 0.09 (s, 3H), 0.07 (s, 3H), 0.06 (s, 6H), 0.05 (s, 6H), 0.04 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 159.2, 144.4, 144.3, 134.3, 133.0, 132.4, 130.5, 129.1, 128.6, 127.6, 126.7, 113.8, 86.7, 85.4, 79.8, 75.1, 73.8, 72.2, 66.4, 65.0, 55.0, 42.3, 41.6, 41.5, 40.5, 37.1, 35.8, 34.8, 32.0, 31.9, 30.7, 26.2, 25.94, 25.86, 20.3, 19.2, 18.4, 18.1, 18.0, 15.6, 15.2, 13.2, 10.0, −3.0, −3.4, −3.8, −3.9, −4.2, −4.28, −4.34, −4.4; LRMS (ESI) 1329.8 [M+Na]+, 707.3, 413.2, 243.1; HRMS (ESI) calcd for C78H130O8Si4Na 1329.8741 [M+Na]+, found 1329.8779; [α]20D−8.9 (c 0.46, CHCl3).
