D-glycero-Pent-2-enono-1,4-lactone (trivial name: D-erythroascorbic acid) occurs in the phytopathogen, Sclerotinia sclerotiorum (Lib.) de Bary, where it has a potential role as precursor of oxalic acid. On Glc/yeast/malt medium, S. sclerotiorum produces only nominal amounts of D-erythroascorbic acid but even partial replacement of Glc by D-Ara increases production of erythroascorbic acid and oxalic acid. Use of D-[1-14C]-, -[3-14C]-, or -[6-14C]Glc and D-[5-3H]-, -[2-14C,5-3H]-, or -[UL-14C]Ara provide additional information on erythroascorbic acid biosynthesis and cleavage. The latter process resembles that obtained by peroxygenation of erythroascorbic acid in alkaline solution. An unknown erythroascorbic acid-like compound also occurs in both Glc- and Ara-based cultures.