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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.

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Crocipodin (I), a Benzotropolone Pigment from the Mushroom Leccinum crocipodium (Boletales). -[isolation, structure elucidation and synthesis]. -(KERSCHENSTEINER, L.; LOEBERMANN, F.; STEGLICH*, W.; TRAUNER, D.; Tetrahedron 67 (2011) 8, 1536-1539, http://dx.