Yellow Pigments of Aspergillus niger and Aspergillus awamori

Part II. Chemical Structure of Aurasperone A

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Alkaline degradation of Aurasperone A, C₃₂H₂₆O₁₀, gave a binaphthyl (IIa), m. p. 255°C and acetone. (Ila) afforded a tetraacetate (IIb), C₃₂H₃₀O₁₂ m. p. 219°C and_??_tetramethyl ether (IId), C₂₈H₃₀O₈, m. p. 188°C. These facts along with the NMR spectra of aura-sperone A and (IIb) confirm that aurasperone A is a dimeric 2-methyl-5-hydroxy-6, 8-dimethoxy-4H-naphtho [2, 3-b] pyran-4-one with asymmetric C-C linkage (7-10' or 9-10'). The ether (IId) is not identical with 1, 1', 3, 3', 6, 6', 8, 8'-octamethoxy-4, 4'-binaphthyl. Thus, it follows that (IId) is a 2, 4'-binaphthyl and hence aurasperone A is 2, 2'-dimethyl-5, 5'-dihydroxy-6, 6', 8, 8'-tetrahydroxy-7, 10'-bi [4H-naphtho [2, 3-b] pyran-4-one] (I).