Reaction Steps
Prepared according to the general procedure from 3-(tert-butyldimethylsilyloxy)-2-chloropropanal and (E)-ethyl 2-oxo-4-p-tolylbut-3-enoate using 2 mol % 1 as the catalyst in 83% yield as a single diastereomer (white solid). [α]D2 (c 1.27, CHCl3)=+244.6; mp=60-61° C.; 1H NMR (400 MHz, CDCl3) δ 7.32-7.24 (m, 3H), 7.12 (d, 2H, J=8.1 Hz), 6.99 (d, 2H, J=8.1 hz), 6.70 (d, 1H, J=7.5 Hz), 4.32 (q, 1H, J=7.2 Hz), 3.77 (t, 1H, J=6.8 Hz), 2.81 (q, 1H, J=6.8 Hz), 2.33 (s, 3H), 1.72-1.63 (m, 2H), 1.37-1.14 (m, 19H), 0.88 (t, 3H, J=6.8 Hz); 13C NMR (100 MHz, CDCl3) δ 167.3, 160.7, 142.6, 138.2, 132.0, 129.8, 128.5, 118.9, 62.1, 58.7, 45.8, 38.3, 26.0, 21.3, 18.3, 14.4, −5.3, −5.4; IR (thin film) ν 3027, 2953, 2929, 2857, 1776, 1740, 1658, 1471, 1370, 1317, 1262, 1084 cm−1; HRMS (EI) calcd for C25H36O4 [M-Bu]+ 347.1315, found 347.1305; 95% ee (4S,5R)-isomer as determined by HPLC (AD-H, 100:1 hexanes/i-PrOH), tr (4S,5R)=8.5 min, tr (4R,5S)=10.0 min.
