Reaction Steps
To a solution of 4a (500 mg, 1.44 mmol) in dry CH2Cl2 (20 mL) at 0° C. was added DMAP (88 mg, 0.72 mmol), imidazole (196 mg, 2.88 mmol) and tert-butylchlorodimethylsilane (239 mg, 1.59 mmol). The reaction mixture was allowed to warm up to room temperature and stirred for 24 h. Water (10 mL) was then added, the organic layer was separated, dried (MgSO4), concentrated and submitted to silica gel chromatography (Solvent B) to obtain 5a (583 mg, 88%) as a syrup: [α]D20 +38.0° (c 1.1, CHCl3); 1H NMR (CDCl3): δ -0.04 (s, 3 H, --SiCH3), 0.14 (s, 3 H, --SiCH3), 0.87 [s, 9 H, --C(CH3)3 ], 0.97 (d, 3 H, J=6.88 Hz, --CHCH3), 1.00 (t, 3 H, J=7.44 Hz, --CH2CH2CH3), 1.38 and 1.40 (2d, 6 H, J=6.0 Hz, --CH(CH3)2), 1.62 (m, 2 H, --CH2CH2CH3), 2.59 (q, 1 H, J=6.9 Hz, --CHCH3), 2.86 (bt, 2 H, --CH2CH2 CH3), 4.62 [m, 1 H, J=6.06 Hz, --CH(CH3)2 ], 4.95-5.05 (m, 2 H, --CH=CH2), 5.29 [d, 1 H, J=6.5 Hz, --CHOSi(CH3)2 --], 5.85 (m, 1 H, --CH=CH2), 5.89 (s, 1 H, H-3), 6.24 (s, 1 H, H-6), 9.15 (s, 1 H, ArOH); 13C NMR (CDCl3): δ -0.33, -0.15, 13.91, 16.27, 18.06, 21.76, 21.85, 23.08, 25.68, 25.88, 38.96, 44.62, 70.67, 74.28, 97.54, 103.39, 106.57, 109.86, 115.71, 139.60, 152.98, 156.13, 158.95, 160.17, 160.75. Anal. Calcd for C26H40 O5Si: C, 67.78; H, 8.75. Found C, 67.91; H, 8.71.
