Secondary metabolites of Diaporthe cameroonensis, isolated from the Cameroonian medicinal plant Trema guineensis

• Bel Youssouf G. Mountessou,
• Élodie Gisèle M. Anoumedem,
• Blondelle M. Kemkuignou,
• Yasmina Marin-Felix,
• Frank Surup,
• Marc Stadler and
• Simeon F. Kouam

Beilstein J. Org. Chem. 2023, 19, 1555–1561, doi:10.3762/bjoc.19.112

• cereals [31]. The isolation of the alternariol compound in this study is not surprising because it has been reported that dibenzo-α-pyrones are also found in mycobionts, plants, some animal dung, and endophytes [32][33]. Although the toxicity of dibenzo-α-pyrones is not fully understood and varies amongst

• cellular systems [31], alternariols have been identified in various bioassay systems as toxic compounds [34]. Furthermore, the estrogenic potential of alternariols and their inhibitory effects on cell proliferation have been demonstrated [35], and several other beneficial bioactivities of dibenzo-α-pyrones

• have been reported [32]. The importance of dibenzo-α-pyrones is manifold as they can also be used as key intermediates in the synthesis of therapeutic compounds [32]. Since compound 1 was isolated as a racemic mixture, while compound 2 is a diacetylated derivative of the mycotoxin alternariol known for

Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

• Natascha Breuer,
• Irina Gruber,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262

• Strukturchemie, Universitätsstraße 1, D-40225 Düsseldorf, Germany 10.3762/bjoc.15.262 Abstract Starting from substituted alkynones, α-pyrones and/or 1H-pyridines were generated in a Michael addition–cyclocondensation with ethyl cyanoacetate. The peculiar product formation depends on the reaction conditions as

• well as on the electronic substitution pattern of the alkynone. While electron-donating groups furnish α-pyrones as main products, electron-withdrawing groups predominantly give the corresponding 1H-pyridines. Both heterocycle classes fluoresce in solution and in the solid state. In particular

• , dimethylamino-substituted α-pyrones, as donor–acceptor systems, display remarkable photophysical properties, such as strongly red-shifted absorption and emission maxima with daylight fluorescence and fluorescence quantum yields up to 99% in solution and around 11% in the solid state, as well as pronounced

Indenopyrans – synthesis and photoluminescence properties

• Andreea Petronela Diac,
• Ana-Maria Ţepeş,
• Albert Soran,
• Ion Grosu,
• Anamaria Terec,
• Jean Roncali and
• Elena Bogdan

Beilstein J. Org. Chem. 2016, 12, 825–834, doi:10.3762/bjoc.12.81

• trifluoromethylated heterocycles, such as indone and carbostyril derivatives. Based on their important biological functions in nature and the synthetic potential of α-pyrones for the construction of a variety of fluorescent heteroarenes, we decided to synthesize and study the optoelectronic properties of some indeno

• -benzoquinone (DDQ), led to indeno-α-pyrones 4–6 (Scheme 2), in not very satisfying yields. Investigations carried out for the dehydrogenation reaction of the isomeric mixture 2'a/3''a (Scheme 2) revealed the formation of the α-pyrone 6a (15% yield), which was the oxidation product of isomer 3''a. In the same

• revealed the formation of the fully oxidized derivative 6c in small amounts that could not be isolated. However, silica gel column chromatography of the reaction mixture allowed the recovery of the starting enol-lactone derivative 2'c in 50% yield. The 1H NMR spectra of α-pyrones 4c and 5c (Figure S4

Biosynthesis of α-pyrones

• Till F. Schäberle

Beilstein J. Org. Chem. 2016, 12, 571–588, doi:10.3762/bjoc.12.56

• mechanisms, yielding in such six-membered unsaturated ester ring residues have been obtained. The purpose of this mini-review is to give a brief overview of α-pyrones and the mechanisms forming the basis of their natural synthesis. Especially the chain interconnecting enzymes, showing homology to

• ketosynthases which catalyze Claisen-like condensation reactions, will be presented. Keywords: α-pyrones; biological activity; interconnecting ketosynthases; natural product; polyketides; Introduction α-Pyrones (1, also 2-pyrones) represent a moiety widespread in nature (Figure 1). The motif of a six-membered

• cyclic unsaturated ester is present in a large number of natural products, and molecules containing α-pyrones can be found in all three kingdoms of life. Additionally α-pyrones, especially the structurally simple ones, i.e., triacetic acid lactone (2) and tetraacetic acid lactone (3) (Figure 1

A novel and widespread class of ketosynthase is responsible for the head-to-head condensation of two acyl moieties in bacterial pyrone biosynthesis

• Darko Kresovic,
• Florence Schempp,
• Zakaria Cheikh-Ali and
• Helge B. Bode

Beilstein J. Org. Chem. 2015, 11, 1412–1417, doi:10.3762/bjoc.11.152

• activity [10][11] might be disturbed in a R121D variant resulting in a loss of KS activity. Other examples of α-pyrones derived from a two-chain condensation of two acyl moieties are myxopyronin [22] and corallopyronin [23] that require a similar KS encoded by mxnB and corB, respectively. Both natural

• the potent antibiotics myxopyronin and corallopyronin. Structures of photopyrones 1–8, pseudopyronines 9–11, myxopyronin A (12) and corallopyronin A (13). For all α-pyrones the western (red) and the eastern (blue) acyl moiety is highlighted. Dimeric structure of modeled PpyS (A). Chain A (blue), chain

Pd/C-mediated synthesis of α-pyrone fused with a five-membered nitrogen heteroaryl ring: A new route to pyrano[4,3-c]pyrazol-4(1H)-ones

• Dhilli Rao Gorja,
• Venkateswara Rao Batchu,
• Ashok Ettam and
• Manojit Pal

Beilstein J. Org. Chem. 2009, 5, No. 64, doi:10.3762/bjoc.5.64

• acid, involving the first regioselective construction of α-pyrone ring on a pyrazol moiety via tandem coupling–cyclization process, has been developed to afford pyrano[4,3-c]pyrazol-4(1H)-one in a single pot. Keywords: C–C bond; catalysis; palladium; pyrazole; pyrone; Introduction α-Pyrones [1][2

• ] (or 2H-pyran-2-one) and their benzo derivatives, e.g. isocoumarins [3], have shown a wide range of pharmacological activities [4][5][6] such as antifungal, antimicrobial, phytotoxic and other effects. On the other hand α-pyrones fused with a five-membered heteroaryl ring, e.g. thienopyranones, have

• both the pyrazole and the pyrone moiety would be responsible for enhanced anabolic activity of the individual parent compounds. Because of our longstanding interest in the synthesis of pyrone derivatives of potential pharmacological interest we decided to explore the synthesis of α-pyrones fused with a