The acid catalyzed condensations of ketones with glyoxylic acid at 80 °C, under neat conditions gives 4-oxo-2,5-heptdienedioic acids in 56–88% yield. The solid state photochemical dimerization of 4-oxo-2,5-heptdienedioic acid under UV light gives 2,7-dioxo-tricyclo[6.2.0.03,6]decane-4,5,9,10-tetracarboxylic acid in 90% yield. (Figure presented.).