Reaction Steps
Sodium hydroxide (5 mL, 0.1 M, 0.5 mmol) was added slowly to a stirred solution of 28 (100 mg, 0.19 mmol) in THF (5 mL). The resulting mixture was stirred for 2 h at room temperature. The organic solvent was evaporated and the aqueous solution was acidified with HCl to pH=2, extracted with ethyl acetate, and extract was concentrated to give 29 as a white solid (66 mg, 70%). mp 130° C. [α]D26+35.1° (c 1.2, CH3OH). 1H NMR (CD3OD, 500 MHz) 60.11 (s, 3H, CH3), 0.14 (s, 3H, CH3), 0.91 (s, 9H, 3CH3), 1.32 (s, 3H, CH3), 1.39 (s, 3H, CH3), 2.0 (s, 3H, NAc), 3.66 (s, 2H, OCH2), 3.98 (m, 2H), 4.14 (t, J=8.0 Hz, 1H), 4.20 (t, J=8.0 Hz, 1H), 4.27 (m, 1H, H-6), 4.33 (m, 1H), 4.63 (m, 1H, H-4), 5.84 (s, 1H, H-3). 13C NMR (CD3OD, 125 MHz) δ −4.65, −4.45, 18.81, 23.19, 25.43, 26.18, 26.61, 30.89, 51.97, 66.47, 68.13, 68.79, 70.76, 77.71, 78.38, 78.68, 109.35, 113.37, 144.93, 164.97, 173.24, 173.61. ESIMS calcd for C22H37NO10SiNa [M+Na]+ 526.3. Found 526.3. Anal. Calc. for C22H37NO10Si: C, 52.47; H, 7.41; N, 2.78. Found: C, 52.38; H, 7.48; N, 2.64.
