Synthesis and biological evaluation of 9Z-retinoic acid analogs having 2-substituted benzo[b]furan.

Palladium-catalyzed cross-coupling reactions of a 2-substituted 3-iodobenzo[b]furans and stannanyl ester afforded the stereoselective production of 9Z-retinoic acid ester analogs in good yields. These esters were then converted to the corresponding acids via basic hydrolysis in excellent yields, and their biological activities were evaluated. The analog changed the connected position of polyene side chain from 2-position to 3-position of benzo[b]furan decreased the biological activities dramatically, and the introduction of various substituents at 2-position afforded almost no effect on the activities.