Reaction Steps
Prepared according to the general procedure from 3-(tert-butyldimethylsilyloxy)-2-chloropropanal and (E)-methyl 4-oxo-4-phenylbut-2-enoate using 0.5 mol % 1 as the catalyst in 80% yield as a 3:1 mixture of diastereomers. The diastereomers were separated by silica gel chromatography (15:1 hexanes/EtOAc) and characterized separately. [α]D20 (c 1.07, CHCl3)=+133.6; 1H NMR (400 MHz, CDCl3) δ 7.65-7.62 (m, 2H), 7.40-7.37 (m, 3H), 5.94 (d, 1H, J=7.1 Hz), 4.26 (dd, 1H, J=10.6, 5.7 Hz), 3.88 (t, 1H, J=10.1 Hz), 3.76 (dd, 1H, J=13.7, 7.4 Hz), 3.72 (s, 3H), 3.08-3.02 (m, 1H), 0.89 (s, 9H), 0.07 (s, 3H), 0.06 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 170.9, 167.7, 152.5, 131.9, 129.8, 128.8, 125.0, 98.1, 59.7, 52.6, 42.5, 38.7, 25.9, 18.4, −5.4, −5.6; IR (thin film) ν 3062, 2953, 2929, 2886, 2857, 1778, 1739, 1254, 1197, 1176 cm−1; HRMS (EI) calcd for C20H25O5Si [M]+ 376.1706, found 376.1697; 97% ee (3R,4S)-isomer as determined by HPLC (AD-H, 100:1 hexanes/i-PrOH), tr (3R,4S)=21.8 min, tr (3S,4R)=15.2 min.
