Acid-Treatment of Arylpropanoid and Arylethanoid Derivatives – Access to Natural and Synthetic Biologically Active Polyphenols

The acid-treatment of arylpropanoid derivatives may lead to numerous polyphenols presenting a wide variety of biological properties such as antiinflammatory, anticancer and antiviral activities and may constitute an alternative route to neolignans to the classical oxidative dimerisation of arylpropenoid compounds. Firstly, I will present the acidic dimerisation of arylethanals, aryllactic acids and 2-aminoarylpropanoic acids. The access to 2-arylnaphthalenes, epoxydibenzocyclooctenes or substituted pavinans may be easily controlled by the acidic conditions. Some natural polyphenols may be obtained. Then, the facile conversion of arylacetones into substituted 1,3-dimethyl-2-arylnaphthalenes using boron tribromide as dimerisation and demethylation agent will be examined. Next, acid-treatment of arylpyruvic acids will be discussed. Depending on the acidic conditions, arylpyruvic acids may simply be isomerised, cyclised into benzofurans or benzocoumarins or dimerised into vitamin C analogues. Lastly, the easy conversion of methoxylated stilbenes into 2-arylbenzofurans presenting the structural feature of moracins or norlignans will be presented. Finally, the biological relevance of the present molecules will be also deeply discussed.