Reaction Steps
Retinyl 2,5-Dimethoxybenzyl Ether (3b) was prepared from retinol and 2,5-dimethoxybenzyl bromide according to the procedure for 3a. The crude product was subjected to chromatography in chloroform on a column of silica gel 60. Successive chromatographic purifications of eluted portions were performed on columns of silica gel 60 with chloroform, 7:3 hexane-ethyl acetate, or 1:1 chloroform-hexane as eluting solvents. The progress of the purification of the original crude product and of fractions from the successive chromatographic operations was monitored by TLC and HPLC. The purified specimens from each chromatographic procedure were combined in ethanol, and the ethanol solution was concentrated in vacuo to a yellow syrup: yield, 16%; HPLC, 100%; MS m/z 436 (M), 285 (C20H29O), 269 (C20H29),255 (C19H17),151 (2,5-dimethoxybenzyl); UV λmax326 um (ε 51 600),225 nm (ε 12 600), ε calculated for C29H40O3.C2H5OH; 1H NMR (CDCl3) δ 6.99 (bs, 1H, H6′), 6.80 (d, 1H, H3′, J3′,4′=8.1 Hz), 6.77 (dd, 1H, H4′, J4′,6′=1.5 Hz), 6.59 (dd, 1H, H11, J10,11=11.0 Hz, J11,12=15.1 Hz), 6.30 (d, 1H, H12), 6.16 (bd, 1H, H8, J7,8=16.1 Hz), 6.10 (d, 1H, H7), 6.09 (d, 1H, H10), 5.71 (t, 1H, H14), 4.54 (s, 1H, H21), 4.23 (d, 2H, H15, J14,15=6.7 Hz), 3.79 (s, 3H, OCH3), 3.77 (s, 3H, OCH3), 2.01 (t, 2H, H4), 1.95 (d, 3H, H19, J10,19=0.7 Hz), 1.85 (d, 3H, H20, J14,20=0.8 Hz), 1.71 (s, 3H, H18),1.65-1.57 (m, 2H, H3), 1.48-144 (m, 2H, H2), 1.02 (s, 6H, H16, H17). Anal. Calcd. for C29H40O3.C2H5OH: C, 77.15; H, 9.61. Found: C, 77.16; H, 9.23.
