Reaction Steps
1,5-Cyclooctadiene-bis(methyldiphenylphosphine)iridium hexafluorophosphate (25 mg, 20 μmol) was dissolved THF and the resulting red solution was degassed in an argon stream. Hydrogen was then bubbled through the solution, causing the colour to change to yellow. The solution was then degassed again in an argon stream. A solution of 210 (1.4 g, 3.12 mmol) in THF was degassed and added. The mixture was stirred at rt overnight, then concentrated to dryness. The residue was dissolved in a solution of I2 (1.37 g, 5.4 mmol) in 30 mL of THF/H2O (15:4). The mixture was stirred at rt for 1 h, and THF was evaporated. The resulting suspension was taken up in DCM, washed twice with water, satd aq NaHSO3, water, satd aq NaHCO3, water and satd aq NaCl, successively. The organic layer was dried and concentrated. The residue was eluted from a column of silica gel with 7:3 to 6:4 Cyclohexane-EtOAc to give the corresponding hemiacetal 211 (1.3 g, 93%). 1H NMR: δ 7.40-7.30 (m, 10H, Ph), 5.40 (dq, 1H, J1,2=1.8, J2,3=3.4 Hz, H-2), 4.93 (d, 1H, J=10.8 Hz, CH2Ph), 4.78 (d, 1H, J1,2=1.6 Hz, H-1), 4.78 (d, 1H, J=11.2 Hz, CH2Ph), 4.63 (d, 1H, CH2Ph), 4.51 (d, 1H, CH2Ph), 3.99 (m, 1H, J3,4=9.5 Hz, H-3), 3.78 (dq, 1H, J4,5=9.5, J5,6=6.2 Hz, H-5), 3.43 (pt, 1H, H-4), 2.80 (m, 4H, Lev), 2.19 (s, 3H, Ac), 1.37 (d, 3H, H-6). Anal. Calcd for C28H34O7: C, 67.86; H, 6.83. Found: C, 67.94; H, 6.87.
