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

• -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

• calculated quantum yields relative to 9,10-diphenylanthracene were quite low (<1%). In the crystals of α-pyrone 6a, the asymmetric unit consists of a single molecule. The two phenyl rings attached to the pyran-3-one moiety are disposed in a staggered conformation. The angle between the planes defined by the

Antibiotics from predatory bacteria

• Juliane Korp,
• María S. Vela Gurovic and
• Markus Nett

Beilstein J. Org. Chem. 2016, 12, 594–607, doi:10.3762/bjoc.12.58

• Mxf50 [95][96]. Later, the structurally related corallopyronins were found in different strains of Corallococcus coralloides [97][98][99]. Myxopyronins and corallopyronins share a common scaffold composed of a central pyrone ring carrying two flexible side chains (Figure 3). Structural variability

Biosynthesis of α-pyrones

• Till F. Schäberle

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

• Till F. Schaberle Institute for Pharmaceutical Biology, University of Bonn, Nußallee 6, 53115 Bonn, Germany 10.3762/bjoc.12.56 Abstract The α-pyrone moiety is a structural feature found in a huge variety of biologically active metabolites. In recent times new insights into additional biosynthetic

• (Figure 1) [7]. α-Pyrones have also been shown to be HIV protease [8][9][10] and selective COX-2 inhibitors [11][12], and further, signaling functions were attributed to them. Already in the 1990s an unusual dialkyl-substituted α-pyrone (supellapyrone, 7) was detected to be the cockroach sex pheromone [13

• formation yielding in the α-pyrone moiety can be accomplished in different ways. The different biosynthetic routes towards an α-pyrone ring will be presented. The biosynthetic mechanisms to yield saturated lactones, like the statin drug lovastatin, which is in application for lowering cholesterol, will not

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

• mechanism of pyrone formation has been investigated by amino acid exchange and bioinformatic analysis. Additionally, the evolutionary origin of PpyS has been studied by phylogenetic analyses also revealing homologous enzymes in Pseudomonas sp. GM30 responsible for the biosynthesis of pseudopyronines

• including a novel derivative. Moreover this novel class of ketosynthases is only distantly related to other pyrone-forming enzymes identified in the biosynthesis of the potent antibiotics myxopyronin and corallopyronin. Keywords: cell–cell communication; ketosynthase; photopyrones; pseudopyronines; quorum

• sensing; Introduction Chemical compounds containing an α-pyrone moiety are widespread in nature [1][2] and show a high diversity in their biological activity. Members of this class of compounds have been identified with antimicrobial, cytotoxic [3] and antitumor activities [4], as HIV protease inhibitors

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• in chlorobenzene yielded bisketenes 325a and 325b. These two ketene derivatives underwent an intramolecular cycloaddition to afford a 1:1 mixture of 326 and 327 (96%, Scheme 57). On heating with concentrated HCl, 326 and 327 were transformed to pyrone derivative 328 (89%). A solution of the compound

Natural phenolic metabolites with anti-angiogenic properties – a review from the chemical point of view

• Qiu Sun,
• Jörg Heilmann and
• Burkhard König

Beilstein J. Org. Chem. 2015, 11, 249–264, doi:10.3762/bjoc.11.28

• ·Et2O gave genistein (60) in good yield. In the Friedel–Crafts acylation, BF3·Et2O was used as the catalyst and solvent. The following formation of the pyrone was also catalyzed by BF3·Et2O, and a convenient one-pot synthesis of 60 was achieved without isolation of 59 [85]. Fisetin and quercetin The

4-Hydroxy-6-alkyl-2-pyrones as nucleophilic coupling partners in Mitsunobu reactions and oxa-Michael additions

• Michael J. Burns,
• Thomas O. Ronson,
• Richard J. K. Taylor and
• Ian J. S. Fairlamb

Beilstein J. Org. Chem. 2014, 10, 1159–1165, doi:10.3762/bjoc.10.116

• , which are found embedded in a number of natural products. Keywords: heterocycles; Mitsunobu reaction; oxa-Michael addition; 2-pyrone; vinyl ethers; Introduction The 2-pyrone motif is a prevalent structural feature of many complex natural products and biologically active compounds [1][2]. Various

• is generally well-developed [7], efficient routes to these types of complex structural units are elusive, and the total synthesis of these and similar natural products remains a challenge [8]. Simple 2-pyrones such as 4-hydroxy-6-methyl-2-pyrone (triacetic acid lactone, 3a, Figure 1) are readily and

• cheaply available, making them seemingly ideal building blocks for the synthesis of such complex pyrone-containing molecules. As heterocyclic aromatic enols, they have a high acidity and dense functionality which leads to a diverse reactivity profile. This means that 4-hydroxy-2-pyrones are also useful

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• sequence via the corresponding 2-pyrone (e.g. Scheme 9), which is converted to the 2-pyridone through an exchange with ammonia or an equivalent nitrogen source (NH4X; X = Cl, Br, I, OAc, OH). However, more conveniently the 2-pyrone precursor can be generated via the vacuum pyrolysis of coumalic acid (1.56

Alternaric acid: formal synthesis and related studies

• Michael C. Slade and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2013, 9, 166–172, doi:10.3762/bjoc.9.19

• appendage of the pyrone moiety [24]. Conclusion In conclusion, we have described the application of silyl glyoxylate three-component-coupling reactions as the central feature of three distinct approaches to the total synthesis of alternaric acid. By judicious choice of coupling partner and reaction

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

• shown anticancer properties in vitro [7]. Recently, incorporation of another five-membered ring, e.g. pyrazole pyrone moieties in a single molecule (A, Figure 1) has been reported to provide polycyclic azaheteroaromatics with a steroid-like skeleton [8]. This initiative was based on the assumption that

• 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

A short stereoselective synthesis of (+)-(6R,2′S)-cryptocaryalactone via ring- closing metathesis

• Palakodety Radha Krishna,
• Krishnarao Lopinti and
• K. L. N. Reddy

Beilstein J. Org. Chem. 2009, 5, No. 14, doi:10.3762/bjoc.5.14

• anti-inflammatory activity [24]. The styryl-pyrone skeleton is often found in natural products from Equisetaceae and also from the primitive angiosperm families, such as Lauraceae, Piperaceae, Ranunculaceae and Zingiberaceae. Cryptocaryalactone 1 [25][26], kurzilactone (2) [27], goniothalamin (3) [28

Synthesis of spiropyrans: H-abstractions in 3-cycloalkenyloxybenzopyrans

• Satish C. Gupta,
• Mandeep Thakur,
• Somesh Sharma,
• Urmila Berar,
• Surinder Berar and
• Ramesh C. Kamboj

Beilstein J. Org. Chem. 2007, 3, No. 14, doi:10.1186/1860-5397-3-14

• can be visualized as having occurred through an initial abstraction of the O-methine proton of cycloalkenyl group by the excited carbonyl of the pyrone moiety to produce 1,4-biradical 8. The photoproduct 5 (a, b, c, d), is then formed through bond formation between the alkoxy radical and furan (8