Lithium 3-Lithio-3-tosylalkanoates: .beta.-Acylvinyl Anion Equivalents of .beta.-Lithiated .alpha.,.beta.-Unsaturated Carboxylic Acids

Strategies for the construction of γ-spirocyclic butenolides in natural product synthesis

Over the last four decades, a number of γ-spirocyclic butenolide containing natural products, drugs, and medicinally useful synthetic compounds have been reported. In this review, we discuss diverse chemical approaches to synthesize γ-spiro butenolides and their application towards natural product synthesis. The collective perception of various methods may allow superior approaches capable of delivering efficient synthetic approaches to obtain γ-spiro butenolide comprising natural products and their hybrid analogues for further drug discovery and development.

Oxylipins Associated to Current Diseases Detected for the First Time in the Oxidation of Corn Oil as a Model System of Oils Rich in Omega-6 Polyunsaturated Groups. A Global, Broad and in-Depth Study by 1H NMR Spectroscopy

For the first time, an important number of oxylipins have been identified and quantified in corn oil submitted to mild oxidative conditions at each time of their oxidation process. This oil can be considered as a model system of edible oils rich in polyunsaturated omega-6 groups. The study was carried out using 1H nuclear magnetic resonance spectroscopy (1H NMR), which does not require chemical modification of the sample. These newly detected oxylipins include dihydroperoxy-non-conjugated-dienes, hydroperoxy-epoxy-, hydroxy-epoxy- and keto-epoxy-monoenes as well as E-epoxy-monoenes, some of which have been associated with several diseases. Furthermore, the formation of other functional groups such as poly-formates, poly-hydroxy and poly-ether groups has also been proven. These are responsible for the polymerization and increased viscosity of the oil. Simultaneously, monitoring of the formation of well-known oxylipins, such as hydroperoxy-, hydroxy-, and keto-dienes, and of different kinds of oxygenated-alpha,beta-unsaturated aldehydes such as 4-hydroperoxy-, 4-hydroxy-, 4-oxo-2E-nonenal and 4,5-epoxy-2E-decenal, which are also related to different degenerative diseases, has been carried out. The provided data regarding the compounds identification and their sequence and kinetics of formation constitute valuable information for future studies in which lipid oxidation is involved, both in food and in other scientific fields.

A structure-taste study of arylsulfonyl(cyclo)alkanecarboxylic acids

A number of sweeteners contain a sulfonyl group. In our current search for new glucophores several new compounds containing such group were obtained. A series of novel 1-phenylsulfonylcyklohexanecarboxylic acids and 2-arylsulfonylalkanecarboxylic acids was obtained and evaluated for their sweet taste quality. It has been found that methyl substituents are of the key importance for the activity of these compounds.

Zinc carbenoid-mediated chain extension: preparation of alpha,beta-unsaturated-gamma-keto esters and amides

An efficient one-pot preparation of alpha,beta-unsaturated-gamma-keto esters and amides has been developed. A zinc carbenoid-mediated chain extension of a beta-dicarbonyl substrate provides access to an intermediate zinc enolate, which is treated sequentially with a halogen and amine base. This method has been applied to a variety of ester and amide starting materials, as well as to amino acid-derived substrates and to a formal synthesis of (R,R)-(-)-pyrenophorin.

Efficient Conditions for Conversion of 2-Substituted Furans into 4-Oxygenated 2-Enoic Acids and Its Application to Synthesis of (+)-Aspicilin, (+)-Patulolide A, and (-)-Pyrenophorin

2-Substituted furans 1a,b,c were found to be conveniently transformed into trans 4-oxo-2-enals 2a,b,c in 62-87% yields by using NBS/pyridine in THF-acetone-H(2)O (<-15 degrees C then rt) or NBS/NaHCO(3) in acetone-H(2)O (<-15 degrees C then rt after addition of pyridine). Further oxidation of the enals 2a-c using NaClO(2) led to the trans 4-oxo-2-enoic acids 3a-c in good yields. With this transformation in mind, we designed syntheses of (+)-aspicilin, (+)-patulolide, and (-)-pyrenophorin. In the synthesis of (+)-aspicilin as shown in Schemes 1 and 2, the pivotal intermediate 6 was prepared from olefin 7 in which 2-furyl group is attached. The AD reaction of 7 secured the C(5) and C(6) stereochemistry of aspicilin, and the subsequent transformation using the protocol described above afforded the ester 6. Stereocontrolled reduction of 6 followed by deprotection and the Yamaguchi macrocyclization furnished (+)-aspicilin. For the synthesis of (+)-patulolide (Scheme 3) and (-)-pyrenophorin (Scheme 4), the intermediates are the furans 38 and 44, which were prepared easily by the classical methods using furyllithium 33. The furan ring oxidations proceeded as well, furnishing acids 40 and 46 in good yields, acetalization of which afforded the known intermediates 41 and 47, respectively.