A novel synthetic route to cytotoxic 1,4-anthraquinones from 1,4-benzoquinones

A new procedure to obtain anthracene-1,4-diones from p-benzoquinones and myrcene, in the presence of acids, is described. The cycloaddition reaction between α-myrcene and p-benzoquinones, followed by oxidation, led to 1,4-naphthoquinones or 1,4-anthraquinones depending upon whether the Lewis acid used in the Diels-Alder reaction, was present or absent during oxidation; furthermore, traces of acid in the solvents played an important role in determining the cycloadduct obtained. The quinones synthesized exhibited cytotoxicity towards several tumor cell lines.