Preparation and biological evaluation of 5-substituted retinoic acids

Various 5-substituted retinoic acids were prepared by a palladium-catalyzed cross coupling reactions of vinyl nonaflates and E- or Z-3-tributylstannyl-2-beten-1-ol as a key reaction. These coupling products were then converted to the corresponding all-E- and 9Z-retinoic acid analogs via Horner-Emmons reaction and subsequent basic hydrolysis, and their biological activities were evaluated. The all-E-derivatives, 5-butyl and isobutyl analogs exhibited stronger effects for anti-proliferative and differentiation-inducing activities in HL-60 cells. In contrast, in 9Z-derivatives, none of the analogs showed any activity.