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