Abstract Isomaltol (1), an enolic nonenzymic browning-product, decomposes in dilute acid to form the new red-orange colored, symmetrical dimer,(E)-2-[1-(3-hydroxy-2-furanyl) ethylidene]-(2H)-furan-3-one (2). Compound 2 was obtained in 20.4% yield with toluenesulfonic acid (⩾ 3 m) at 50. The structure for 2 was assigned on the basis of spectral data (ms, uv, ir, 13 C-and 1 Hn. mr) and conversion into its mono-O-acetyl derivative (3).
