Summary New routes to 3-hydroxy-4-methyl-3-cyclobutene-1, 2-dione (9), the lowest homologue of the mycotoxine moniliformin are described. A common feature of all pathways is the synthesis of methylcyclobutanes having the oxidation level 6. Precursors, which are easily transformed to 9 by acid catalyzed hydrolysis, include [2+ 21-cycloadducts of in situ generated methyl ketene to tetraethoxyethylene and [2+ 21-photocycloadducts of ...