Retinoic acid analogues. Synthesis and potential as cancer chemopreventive agents

Analogues of retinoic acid have been synthesized as potential chemopreventive agents against epithelial cancer. Ethyl (E)-9-(2-norbornenyl)-3,7-dimethylnona-2,4,6,8-tetraenoate (9), (E)-3,7-dimethyl-9-(2-ethyl-6,6-dimethyl-1-cyclohexen-1-yl)nona-2,4,6,8-tetraenoic acid (25), and 2-(2'-methoxyethoxy)ethyl retinoate (26) displayed good activity in the inhibition of tumor promoter-induced mouse epidermal ornithine decarboxylase assay. (E)-1-(3-Acetoxyphenyl)-4-methyl-6-(2,6,6-trimethyl-1-cyclohexen-1-yl)hexa1,3,5 -triene (34) had low activity. (E)-5-[2,6-Dimethyl-8-(2,6,6-trimethyl-1-cyclohexen-1-yl)octa-1,3,5,7-tetraen-1 -yl]tetrazole (40) was inactive.