QUINAPHTHIN, A BINAPHTHYL QUINONOID SECONDARY METABOLITE PRODUCED BY HELICOON RICHONIS

The aero-aquatic fungus Helicoon richonis (Boudier) Linder produces qu inaphthin 4, an alpha beta'-binaphthyl quinone constituted by union of juglone at position 8 to 3-hydroxyjuglone at position 2. The compound exists as a 6-membered cyclic hemiketal {systematic name 3,6a,9-trihy droxydibenzo [b,kl]xanthene-4,8,13(6aH)-trione}. Methyl iodide in the presence of silver oxide converts quinaphthin into the trimethyl deriv ative of an isomer of the compound. The structures of both compounds h ave been determined by X-ray crystallographic analysis.