Reaction Steps
To a solution of 71 (22.9 mg, 3.2 μmol) in 1:1 THF/AcOH (1.4 mL) was added Zn (5.0 mg, 7.8 μmol, nanosize). The mixture was sonicated for 15 min. More Zn (5.0 mg, 7.8 μmol, nanosize) was added, followed by sonication for a further 15 min. The suspension was filtered through a celite pad, washing with EtOAc several times. The filtrates were washed with sat. NaHCO3, brine, dried over MgSO4 and concentrated under vacuum. The crude residue was passed through a short plug of silica gel eluting with hexane/EtOAc 4:1 to give 17.1 mg (99% yield) of 71a as colorless oil: 1H NMR (400 MHz, CDCl3) δ (m, 6H), 0.96 (t, J=7.9 Hz, 9H), 0.97 (d, J=6.8 Hz, 3H), 1.05 (d, J=6.8 Hz, 3H), 1.11 (s, 3H), 1.26 (s, 3H), 1.44 (s, 9H), 1.84-1.90 (m, 1H), 2.21 (dd, J=6.7 and 17.0 Hz, 1H), 2.36 (dd, J=6.7 and 17.0 Hz, 1H), 3.24-3.29 (m, 1H), 3.44-3.52 (m, 2H), 3.67 (dd, J=3.9 and 8.9 Hz, 1H), 4.36 (dd, J=3.5 and 6.5 Hz, 1H), 4.50 (d, J=12.0 Hz, 1H), 4.54 (d, J=12.0 Hz, 1H), 7.32-7.36 (m, 5H); 13C NMR (100 MHz, CDCl3) δ 5.0, 6.9, 9.7, 13.9, 20.2, 21.8, 28.0, 36.3, 40.8, 41.5, 53.7, 72.5, 72.9, 73.2, 73.6, 80.7, 127.4, 127.5, 128.2, 138.6, 171.0, 221.4; IR (film, NaCl, cm−1) 3502, 2959, 2875, 1731, 1683, 1456, 1366, 1154, 1098, 996, 739; LRMS (ESI) calcd for C30H52O6SiCl3Na [M+Na+] 559.3, found 559.3; [α]23D=−41.0 (c=0.4, CHCl3).
