The sulfuric acid catalyzed condensation of levulinic acid with glyoxylic acid at 80 °C, for 24 h under neat conditions gives 1-methyl-2,8-dioxabicyclo[3.3.0]oct-4-ene-3,7-dione in 92% yield. Catalytic reduction of this unsaturated bis-lactone provides a facile route to produce polyester monomer 1-methyl-2,8-dioxabicyclo[3.3.0]octane-3,7-dione from renewable feedstocks.