Reaction Steps
To a solution of hydroxy aldehyde 54 (21 mg, 41 μmol) in 1,2-dichloroethane (4 mL) was added 2,6-lutidine (72 μL, 620 μmol) and TMSOTf (79 μL, 410 μmol). The mixture was heated at 70° C. for 4.5 h before being cooled, diluted with ethyl ether (50 mL), washed with CuSO4 (20 mL), NaHCO3 (20 mL) and dried (MgSO4). Concentration under reduced pressure and purification by flash chromatography (silica gel, 10% ethyl acetate in toluene) gave pure silyl ether 55 (14 mg; 60%): Colorless oil; Rf =0.29 (silica gel, 70% ethyl ether in petroleum ether); 1H NMR (500 MHz, C6D6) δ9.61 (s, 1 h, CHO), 7.25 (d, J=8.7 hz, 2 h, Ar), 6.79 (d, J=8.7 hz, 2 h, Ar), 5.32 (s, 1 h, CHCN), 5.08 (d, J=14.0 hz, 1 h, allylic CH2), 4.85 (d, J=15.1 hz, 1 h, benzylic CH2), 4.75 (d, J=15.1 hz, 1 h, benzylic CH2), 4.60 (d, J=14.0 hz, 1 h, allylic CH2), 4.24 (dd, J=8.5, 2.2 hz, 1 h, THP anomeric CH), 3.93 (s, 1 h, CHOTHP), 3.74-3.68 (m, 1 h, ketal), 3.58-3.54 (m, 1 h, ketal), 3.30-3.24 (m, 3 h, ketal and THP), 3.29 (s, 3 h, OCH3), 3.03-2.96 (m, 1 h, THP), 1.4-0.9 (m, 6 h, THP), 0.34 (s, 9 h, TMS); IR (film) νmax 2929, 2856, 2211, 1734, 1616, 1513, 1424, 1376, 1247, 1180, 1118, 1035, 946, 910, 847 cm-1 ; HRMS Calcd. for C29H36O9N2Si (M+Na+): 607.2088. Found: 607.2080.
