Three previously undescribed azepino-indole alkaloids, named purpurascenines A−C (1−3), together with the new-to-nature 7-hydroxytryptophan (4) as well as two known compounds, adenosine (5) and riboflavin (6), were isolated from fruiting bodies of Cortinarius purpurascens Fr. (Cortinariaceae). The structures of 1−3 were elucidated based on spectroscopic analyses and ECD calculations. Furthermore, the biosynthesis of purpurascenine A (1) was investigated by in vivo experiments using 13C-labeled sodium pyruvate, alanine, and sodium acetate incubated with fruiting bodies of C. purpurascens. The incorporation of 13C into 1 was analyzed using 1D NMR and HRESIMS methods. With [3-13C]-pyruvate, a dramatic enrichment of 13C was observed, and hence a biosynthetic route via a direct Pictet−Spengler reaction between α-keto acids and 7-hydroxytryptophan (4) is suggested for the biosynthesis of purpurascenines A−C (1−3). Compound 1 exhibits no antiproliferative or cytotoxic effects against human prostate (PC-3), colorectal (HCT-116), and breast (MCF-7) cancer cells. An in silico docking study confirmed the hypothesis that purpurascenine A (1) could bind to the 5-HT2A serotonin receptor’s active site. A new functional 5-HT2A receptor activation assay showed no functional agonistic but some antagonistic effects of 1 against the 5-HT-dependent 5-HT2A activation and likely antagonistic effects on putative constitutive activity of the 5-HT2A receptor.

Pseudohygrophorones A(12) (1) and B(12) (2), the first naturally occurring alkyl cyclohexenones from a fungal source, and the recently reported hygrophorone B(12) (3) have been isolated from fruiting bodies of the basidiomycete Hygrophorus abieticola Krieglst. ex Gröger & Bresinsky. Their structures were assigned on the basis of extensive one- and two-dimensional NMR spectroscopic analysis as well as ESI-HRMS measurements. The absolute configuration of the three stereogenic centers in the diastereomeric compounds 1 and 2 was established with the aid of (3)JH,H and (4)JH,H coupling constants, NOE interactions, and conformational analysis in conjunction with quantum chemical CD calculations. It was concluded that pseudohygrophorone A(12) (1) is 4S,5S,6S configured, while pseudohygrophorone B(12) (2) was identified as the C-6 epimer of 1, corresponding to the absolute configuration 4S,5S,6R. In addition, the mass spectrometric fragmentation behavior of 1-3 obtained by the higher energy collisional dissociation method allows a clear distinction between the pseudohygrophorones (1 and 2) and hygrophorone B(12) (3). The isolated compounds 1-3 exhibited pronounced activity against phytopathogenic organisms.

The Chilean Sepedonium aff. chalcipori strain KSH 883, isolated from the endemic Boletus loyo Philippi, was studied in a polythetic approach based on chemical, molecular, and biological data. A taxonomic study of the strain using molecular data of the ITS, EF1-α, and RPB2 barcoding genes confirmed the position of the isolated strain within the S. chalcipori clade, but also suggested the separation of this clade into three different species. Two new linear 15-residue peptaibols, named chilenopeptins A (1) and B (2), together with the known peptaibols tylopeptins A (3) and B (4) were isolated from the semisolid culture of strain KSH 883. The structures of 1 and 2 were elucidated on the basis of HRESIMS(n) experiments in conjunction with comprehensive 1D and 2D NMR analysis. Thus, the sequence of chilenopeptin A (1) was identified as Ac-Aib(1)-Ser(2)-Trp(3)-Aib(4)-Pro(5)-Leu(6)-Aib(7)-Aib(8)-Gln(9)-Aib(10)-Aib(11)-Gln(12)-Aib(13)-Leu(14)-Pheol(15), while chilenopeptin B (2) differs from 1 by the replacement of Trp(3) by Phe(3). Additionally, the total synthesis of 1 and 2 was accomplished by a solid-phase approach, confirming the absolute configuration of all chiral amino acids as l. Both the chilenopeptins (1 and 2) and tylopeptins (3 and 4) were evaluated for their potential to inhibit the growth of phytopathogenic organisms.

The hygrophorones, a class of cyclopentenones isolated from fruiting bodies of the genus Hygrophorus (basidiomycetes), show promising antifungal activity. While the constitution of 4,6-diacetylhygrophorone A(12) (3) and the relative configuration of the stereogenic centers in the cyclopentenone ring were elucidated using standard NMR and MS techniques, the relative configuration of the exocyclic stereogenic center could not be assigned. By introducing a sample of 3 into an alignment medium and measuring anisotropic NMR parameters, namely, residual dipolar couplings, we were able to unambiguously determine the relative configuration of all three stereogenic centers in 4,6-diacetylhygrophorone A(12) simultaneously by fitting several structure proposals to the experimental data.

Three novel alkaloids (1−3), named pyriferines A−C, were isolated from fruiting bodies of Pseudobaeospora pyrifera. They possess an unusual eight-membered N/O-acetal ring, derived from l-glutamic acid, that is connected to an enolized 1,3-diketo moiety. The structures were determined by spectroscopic methods, and the absolute configuration of the glutamic acid moiety was established using GC-MS after Mosher-type derivatization.

Chemical analysis of the fruiting bodies of the agaricoid fungus Cortinarius subtortus yielded three new natural products, two quinoline and one isocarbostyryl alkaloid. The structures of compounds 1−3 were determined by analysis of NMR and MS data. Compound 1 exhibited inhibitory effects against the phytopathogenic fungus Colletotrichum coccodes. All three compounds displayed moderate antioxidant activity in a DPPH free radical scavenging bioassay.

Four β-carboline alkaloids, brunneins A–C (1–3) and 3-(7-hydroxy-9H-β-carboline-1-yl)propanoic acid (4), were isolated from fruiting bodies of the agaricoid fungus Cortinarius brunneus. The structures of 1–3 were determined by analysis of NMR and MS data, and the structure of compound 4 was determined by comparison with published data. Brunnein A (1) exhibited very low cholinesterase inhibitory effects and no cytotoxicity.

A red pigment, lilacinone (1), was isolated from fruit bodies of the toadstool Lactarius lilacinus. Its structure was established by 2D NMR and APCIMS methods. Compound 1 is a novel type of fungal aminobenzoquinone pigment and may be biosynthetically derived from three molecules of anthranilic acid.