maleic anhydride leads to tricyclic lactone-carboxylic acids through the sequence of esterification and intramolecular Diels–Alder reaction. Anodic oxidative decarboxylation of the hydrogenated products in MeOH affords 1,2,3-trisubstituted cyclopentane derivatives, viz. 1-hydroxymethyl-3-methoxy-2-oxabicyclo[2.2.1]heptane-7-syn-carboxylic lactones, potential intermediates for synthesis of iridoids.