Reaction Steps
Prepared according to the general procedure from 2-chloro-hydrocinnamaldehyde and (E)-methyl 4-oxo-4-furanylbut-2-enoate using 0.5 mol % 1 as the catalyst in 94% yield as an 8:1 mixture of diastereomers (brown oil). [α]D20 (c 1.03, CHCl3)=+119.5; 1H NMR (400 MHz, CDCl3) δ 7.41-7.29 (m, 4H), 7.18-7.16 (m, 2H), 6.67 (d, 1H, J=3.4 Hz), 6.47* (dd, 1H, J=3.2, 2.0 Hz), 6.45 (dd, 1H, J=3.2, 1.6 Hz), 5.74 (d, 1H, J=7.0 Hz), 5.70* (d, 1H, J=6.0 Hz), 3.77 (s, 3H), 3.68* (s, 3H), 3.55 (dd, 1H, J=14.3, 4.7 Hz), 3.52-3.46* (m, 1H), 3.40-3.35* (m. 1H), 3.29-3.26 (m, 1H), 3.15* (dd, 1H, J=13.6, 5.6 Hz), 3.03-2.97 (m, 1H), 2.90* (dd, 1H, J=13.6, 10.0 Hz), 2.74 (dd, 1H, J=14.3, 10.1 Hz); 13C NMR (100 MHz, CDCl3) δ 170.8, 168.4, 146.5, 145.3, 143.7, 138.0, 131.6, 129.6, 129.4, 128.9, 128.8, 127.4, 127.1, 111.8, 109.0, 108.9, 96.4, 94.0, 53.6, 52.9, 52.8, 43.0, 42.6, 40.8, 40.2, 35.5, 33.4; IR (thin film) ν 3063, 3029, 2953, 1781, 1734, 1495, 1455, 1264, 1225, 1201, 1174, 1085, 1009 cm−1; HRMS (ESI) calcd for C18H16O5 [M+Na]+ 335.0889, found 335.0890; 99% ee (3S,4S)-isomer as determined by HPLC (AD-H, 20:1 hexanes/i-PrOH), tr (3S,4S)=31.9 min, tr (3R,4R)=22.6 min.
