Biosynthesis of the xylerythrin-type pigments in Peniophora sanguinea

Elucidation of the Biosynthesis and Degradation of Allantofuranone by Isotopic Labelling and Fermentation of Modified Precursors

“…[21,22] These compounds play an important role as key intermediates in the biosynthesis of fungal pigments, because their oxidative ring opening leads to pulvinic acid or derivatives such as atromentic acid or xerocomic acid, being well described in the literature mostly for basidiomycetes, [13,23] but also for lichens. [24] In further support of the biosynthetic hypothesis for 1, another metabolite (7 a) closely related to a compound reportedly biosynthesized from a terphenyl quinone [13] could be isolated from A. lycopodina. In contrast to the other metabolites discussed above, the structure of allantofuranone (1) is based on an unprecedented scaffold.…”

“…Most of the known terphenyl quinones were isolated from wood-rotting basidiomycetes, [13] but there are some examples known from other fungi such as the ascomycete Ascocoryne sarcoides [20] and lichens such as Sticta coronata. [21,22] These compounds play an important role as key intermediates in the biosynthesis of fungal pigments, because their oxidative ring opening leads to pulvinic acid or derivatives such as atromentic acid or xerocomic acid, being well described in the literature mostly for basidiomycetes, [13,23] but also for lichens. [24] In further support of the biosynthetic hypothesis for 1, another metabolite (7 a) closely related to a compound reportedly biosynthesized from a terphenyl quinone [13] could be isolated from A. lycopodina.…”

“…bles xylerithrin (7 b), [12] which is known to be biogenetically derived from polyporic acid (6), [13] providing additional evidence for the hypothesis presented in Scheme 4, which should in turn be verifiable through a feeding experiment with a labelled polyporic acid derivative.…”

“…[8] Because polyporic acid tautomerizes readily, the location of the 13 C label becomes ambiguous and is thus equally distributed between the ketone and the enol carbon. This tautomerization occurs very rapidly, with the four oxygenated carbons in the quinone coalescing in the 13 C NMR spectrum and forming a single broad signal. [9] The postulated oxidative ring cleavage of polyporic acid (6) yields a product similar to the seco-precursor of 6 existing in the form of two different isotopomers and ultimately leads to allantofuranone with the observed labelling pattern.…”

“…The obtained 13 C-enriched 1 was analysed by 13 C NMR and, surprisingly, equal enrichment was found at four positions (C-2, C-3, C-5, C-6) with 17.7(AE0.60)-fold increases in 13 C (Scheme 3, Table 1). However, no enhancement of the 1 J C,C satellites was observed in the 13 C NMR spectrum and it was concluded that there was no correlated enrichment in the corresponding neighbouring positions. These results ruled out a simple condensation between two phenylpropanoid units because this would have resulted in the exclusive labelling of C-2 and C-5.…”