Studies on the Structure and Biosynthesis of Tridentoquinone and Related Meroterpenoids from the Mushroom Suillus tridentinus (Boletales)

Abstract

Tridentoquinone (1), the main pigment of Suillus tridentinus, is accompanied by the known meroterpenoid bolegrevilol (3) and a dimer, tridentorubin (5). The absolute configuration of 1 was unambiguously established by a single‐crystal X‐ray analysis of the corresponding (–)‐camphanoate. The structure of 5 was elucidated by 2D NMR techniques including a 2D INADEQUATE experiment. Feeding experiments with [1‐13C]‐labeled 4‐hydroxybenzoic acid (6*) and 3,4‐dihydroxybenzoic acid (7*) proved the incorporation of these precursors into all three metabolites. Tridentoquinone (1) was monolabeled at C‐1 suggesting the formation of the ansa ring by oxidative cyclisation of 2‐geranylgeranyl‐6‐hydroxybenzoquinone (10). This was supported by the isolation of the expected intermediate, deoxytridentoquinone (11), from the mushroom extract. Tridentorubin (5) may be formed by addition of precursor 10 to tridentoquinone (1). This hypothesis is backed up by the in vitro formation of an analogous product 13 from 1 and 1,4‐benzoquinone. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Synthetic approaches to regiospecifically mono‐ and dilabelled arenes

“…Other targets of interest are available from ethyl 4‐hydroxybenzoate by saponification, followed by decarboxylation of the resulting acid. This process has been carried out using the classical copper‐promoted method78 but is more conveniently carried out under milder conditions in concentrated hydrochloric acid 79. The labelled phenol obtained has been para ‐iodinated in good yield78 and has also been oxidised to [1‐ 13 C]benzoquinone 79…”

Studies on the Biosynthesis of Bovilactone‐4,4 and Related Fungal Meroterpenoids

“…This negative result allows no conclusions, since difficulties encountered by this lipophilic precursor in reaching the site of biosynthesis cannot be ruled out. [2] The formation of bovilactone-4,4 (3) from deacetylsuillin (9) and boviquinone-4 (2) can be explained by the mechanism depicted in Scheme 6. After oxidation of deacetylsuillin to the corresponding benzoquinone 13, this could then act as a Michael acceptor for boviquinone-4 (2).…”

“…In the first two experiments, bovilactone-4,4 showed the same labelling pattern as that reported for S. bovinus. [4-13 C]-Labelled benzene-1,2,4-triol [16] was not incorporated into suillin or bovilactone-4,4, neither in fruit bodies nor in cultures of S. variegatus, an indication that this potential intermediate [2] does not participate in the biosynthesis of these Suillus meroterpenoids.…”

“…[1,2] Most widely distributed is suillin (1), which was first isolated from S. granulatus and also occurs in several related species. [3] Suillin has strong tumour-inhibiting and cytotoxic activities, [4] and also exhibits immunosuppressive properties.…”

Pigments of higher fungi - a review

“…Singer, which is related to the linear boviquinone-4 (53) from S. bovinus (L.) Roussel. In the mushroom, tridentoquinone is accompanied by several compounds of similar structure (Lang et al 2008). Mushrooms of the genus Rhizopogon Fr.…”