STUDIES ON THE PREPARATION OF BIOACTIVE LIGNANS BY OXIDATIVE COUPLINGREACTION .4. OXIDATIVE COUPLING REACTION OF METHYL (E)-3-(3,4-DIHYDROXY-2-METHOXYPHENYL)PROPENOATE AND LIPID-PEROXIDATION INHIBITORY EFFECTS OF THE PRODUCED LIGNANS

The oxidative coupling reaction of the hydroxycinnamate 11 derived fro m daphnetin has been investigated. The reaction with silver oxide affo rded, after acetylation, a dihydrobenzofuran derivative 17 and a benzo dioxane derivative 16a as major products accompanied with a small amou nt of a bis(benzylidene)succinate 18 and a dihydronaphthalene 19, whil e the oxidation with iron(III) chloride gave the dihydronaphthalene de rivative 20 corresponding to 19. The reaction with potassium hexacyano ferrate(III) and Na2CO3 produced, after acetylation, 16a and 19 in low er yields. The propensity for product formation in the reaction of 11 is discussed in relation to data for the reactions of hydroxycinnamate derivatives studied so far. The obtained compounds were tested for in hibitory effects on lipid peroxidation in rat brain homogenate and rat liver microsomes. In the rat brain homogenate the five compounds show ed inhibitory activity more potent than that of idebenone. Compounds 1 7 and 20 were then tested in rat liver microsomes, and found to be mor e potent than schizotenuin A and much more potent than(+/-)-alpha-toco pherol.