Reaction Steps
The title compound was prepared according to the general procedure from (E)-4-oxopent-2-enal and trans-N-(4-methoxybenzenesulfonyl)-hex-2-en-1-imine using 10 mol % 9 as the catalyst in 70% yield as a yellow oil. [α]D20 (c 0.91, CHCl3)=−5.7; 1H NMR (400 MHz, CDCl3) δ 7.91 (dd, 2H, J=6.9, 2.0 Hz), 6.97 (dd, 2H, J=6.9, 2.0 Hz), 5.54 (dd, 1H, J=8.0, 6.6 Hz), 3.87 (s, 3H), 3.24 (q, 1H, J=6.3 Hz), 2.82 (dd, 1H, J=16.6, 7.2 Hz), 2.41-2.38 (m, 1H), 2.24 (dd, 1H, J=16.6, 7.0 Hz), 1.22 (t, 3H, J=7.2 Hz), 1.25-1.02 (m, 4H), 0.73 (t, 3H, J=7.2 Hz); 13C NMR (100 MHz, CDCl3) δ 206.0, 170.7, 164.1, 131.0, 129.6, 128.8, 124.1, 115.1, 114.4, 114.1, 55.9, 42.4, 39.8, 34.7, 32.1, 30.6, 19.5, 14.3; IR (thin film) ν 3010, 2957, 1713, 1595, 1497, 1362, 1262, 1092, 1023 cm−1; HRMS (ESI) calcd for C18H23NO5S [M+Na]+ 388.1189, found 388.1175; 98% ee (3S,4S)-isomer as determined by HPLC (AS-H, 9:1 hexanes/i-PrOH), tr (3S,4S)=68.1 min, tr (3R,4R)=55.1 min.
