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  • Author: Gertraud Gruber x
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The North American stalked puffball Calostoma cinnabarinum (Boletales) owes its red-orange colour to the heptaene pigment calostomal. Its structure has been determined by 1H and 13C NMR spectroscopy of the corresponding methyl ester as all-trans-16-oxohexadeca-2,4,6,8,10,12,14- heptaenoic acid (1). Neither pulvinic acids nor other typical Boletales pigments could be detected in this fungus. The structural relationship of 1 to other polyene pigments from fungi is discussed.

The close genetic relationship of the mushrooms Retiboletus griseus and R. nigerrimus is supported by the occurrence of the orange-yellow retiboletic acid, resp. its methyl ester, in both species. The structures of these highly substituted pulvinic acid derivatives have been elucidated by spectroscopic investigations. R. nigerrimus also contains two N-protocatechuyl-L-phenylalaninol derivatives, nigerrimin A and B, the first reported occurrence of such compounds in nature. Their configuration was established by the synthesis of nigerrimin B

The pigment responsible for the bright-yellow color of the stalk bases of Leccinum chromapes is methyl isoxerocomate, which is accompanied by lesser amounts of isoxerocomic acid and atromentic acid. In addition, 4ʹ-hydroxy- and 3ʹ,4ʹ-dihydroxyacetophenone, previously unreported as metabolites of Basidiomycetes, were isolated. The pink color of the cap skin is due to variegatorubin. This pigment is accompanied by chromapedic acid, a g-butenolide of biosynthetic interest representing a new dimerization mode of 4-hydroxyphenylpyruvic acid in Boletales.