Reaction Steps
To a solution of 70 (37.6 mg, 6.3 μmol) and imidazole (9.4 mg, 13.8 μmol) in DMF (0.4 mL) at 0° C. was added TESCl (11.6 μL, 69.3 μmol). After 3 h, the mixture was diluted with sat aq NaHCO3. The aqueous layer was extracted three times with hexanes. The combined organic extracts were washed with brine, dried over MgSO4 and concentrated under reduced pressure. The crude product was purified by flash chromatography (gradient hexane to hexane/EtOAc 93:7) to yield, in order of elution, 71 (22.9 mg, 51%), and recovered 70 (12.9 mg, 34%) as clear oils. 7: 1H NMR (400 MHz, CDCl3) δ 0.66 (q, J=7.9 Hz, 6H), 0.96 (t, J=7.9 Hz, 9H), 1.01 (s, 3H), 1.05 (d, J=5.2 Hz, 3H), 1.07 (d, J=5.3 Hz, 3H), 1.35 (s, 3H). 1.44 (s, 9H), 2.05-2.11 (m, 2H), 2.50 (dd, J=3.5 and 17.2 Hz, 1H), 3.35 (dd, J=5.9 and 9.0 Hz, 1H), 3.49 (dd, J=4.0 and 9.0 Hz, 1H), 3.53 (dd, J=3.8 and 6.7 Hz, 1H), 4.18 (dd, J=3.5 and 6.5 Hz, 1H), 4.45 (s, 2H), 4.65 (d, J=11.9 Hz, 1H), 4.79 (d, J=11.9 Hz, 1H), 4.97 (dd, J=3.7 and 8.1 Hz, 1H), 7.29-7.52 (m, 5H); 13C NMR (125 MHz, CDCl3) δ 5.3, 7.3, 10.9, 14.9, 21.3, 22.6, 28.4, 35.9, 41.1, 42.7, 53.7, 71.9, 73.7, 75.7, 80.1, 80.9, 95.1, 127.9, 128.0, 128.7, 138.6, 154.3, 171.7, 215.7; IR (film, NaCl, cm−1) 2956, 2876, 1732, 1694, 1456, 1366, 1257, 1154, 1098, 988, 835, 774, 741; LRMS (ESI) calcd for C33H53O8SiCl3Na [M+Na+] 733.2, found 733.3. [α]23D=−16.1 (c=0.1, CHCl3).
