ISURF #04439 describes a method to perform muconic acid isomerization with high selectivity and good conversion rates by heating the cis-, cis- and/or cis-, trans- muconic acid in conjunction with DMSO or several salt solutions. A benefit of this method is that the resulting isomer can be reacted with a Diels-Alder dienophile in DMSO without any purification or separation after the isomerization reaction.