Synthetic Studies on Viridin Skeleton through Regio- and Stereoselective Functionalization of the AE-Ring Moiety

4,5,6,7-Tetrahydroisobenzofurans, corresponding to the AC(D)E ring structure of viridin and equipped with required substituents on the A-ring, were synthesized via the Diels-Alder adduct of a furan derivative and maleic anhydride with high regio- and stereoselectivities. The key steps of this work include the regioselective opening of the tetrahydrofuran, stereoselective epoxidation, and AlMe3-mediated regioselective epoxide opening followed by stereoselective C-methylation.

Recent Achievement in the Synthesis of Benzo[b]furans

Background: Benzo[b]furan derivatives are oxygen-containing heterocyclic compounds consisting of fused benzene and furan rings and are present in a large number of natural and non-natural compounds. This class of compounds has a wide spectrum of biological activities, such as antiarrhythmic, anticancer, inflammatory, antioxidant, antimicrobial, and antiviral. Furthermore, benzo[b]furan derivatives have also been applied in various areas, such as organic electroluminescence device materials and organic dyes, photosensitizing material, organic synthesis as building blocks or intermediates. : Because of a broad range of applicability, the synthesis of benzo[b]furan derivative has drawn great attention of chemists and many studies on the synthesis of this class of compounds have been reported recently. This review will give an overview of benzo[b]furan preparation based on studies dating back to the year 2012. Objective: In this review, recent development in the synthesis of benzo[b]furans are discussed. There has been increasingly new methodologies for the construction of benzo[b]furans skeleton to improve efficiency or develop environmentally friendly procedures. In some studies, reaction mechanisms were also outlined. Conclusion: Many methods for the synthesis of benzo[b]furans have been reported recently. Most of them involve cyclization or cycloisomerization processes. Unquestionably, more imaginative strategies for the construction of benzo[b]furan skeleton will be established in the near future. Application of known methods to natural products or drug synthesis, on industrial scale for the synthesis of economically or medicinally important benzo[ b]furans will probably be paid attention to.

Differences in xylovolatiles composition between chips or barrel aged wines

Aim: In this research xylovolatile aromatic compounds were determined to highlight any compositional differences between wines aged in barrels and those produced using oak chips.Methods and results: Approximately 200 wines aged using oak chips or wood barrels were analysed, among which about 50 were aged at the experimental winery of the Research Centre of Viticulture and Enology in Asti (Piedmont, Italy). 17 different types of commercial oak chips were used in order to obtain a subset of reference samples. Several factors were considered, including degree of oak wood toasting, wood geographical origin and the type of wine (both red and white). Sample preparation for GC-MS analysis was performed by single-step solid phase extraction, using polymeric SPE cartridges. More than 60 volatile molecules from oak were identified. Analytical results were explained using multivariate statistical analysis. A preliminarily step was carried out using principal component analysis (PCA), which showed interesting compositional differences between barrel and chip-aged wines with regards to methylvanillate, ethylvanillate, as well as furan derivative compounds. Further statistical analysis highlighted the clear impact of the type of wine (red or white) on the extraction of xylovolatile compounds from oak chips. Subsequently, in order to test if and how the selected chemical explanatory variables allow wine treatments to be discriminated, and to predict which group a new observation will belong to, a discriminant analysis (DA) was carried out on an independent dataset. More than 96 % of samples were correctly classified.Conclusions: Significant differences were highlighted between barrel- and chip-aged wines with regards to xylovolatile compounds. The analysis showed that several factors may influence the amount of aromatic compounds extracted from chips and barrels, especially the matrix composition. It was possible to deduce the aging process that the wines had undergone by selecting key molecules using multivariate methods.Significance and impact of the study: Via a suitable GC-MS method and a chemometric approach for the identification of discriminant xylovolatiles in wood aged wines, this study offers promising perspectives and useful tools for routine fraud inspection aiming at classifying wines according to their aging process.

Model Substrate/Inactivation Reactions for MoaA and Ribonucleotide Reductases: Loss of Bromo, Chloro, or Tosylate Groups from C2 of 1,5-Dideoxyhomoribofuranoses upon Generation of an α-Oxy Radical at C3

We report studies on radical-initiated fragmentations of model 1,5-dideoxyhomoribofuranose derivatives with bromo, chloro, and tosyloxy substituents on C2. The effects of stereochemical inversion at C2 were probed with the corresponding arabino epimers. In all cases, the elimination of bromide, chloride, and tosylate anions occurred when the 3-hydroxyl group was unprotected. The isolation of deuterium-labeled furanone products established heterolytic cleavage followed by the transfer of deuterium from labeled tributylstannane. In contrast, 3-O-methyl derivatives underwent the elimination of bromine or chlorine radicals to give the 2,3-alkene with no incorporation of label in the methyl vinyl ether. More drastic fragmentation occurred with both of the 3-O-methyl-2-tosyloxy epimers to give an aromatized furan derivative with no deuterium label. Contrasting results observed with the present anhydroalditol models relative to our prior studies with analogously substituted nucleoside models have demonstrated that insights from biomimetic chemical reactions can provide illumination of mechanistic pathways employed by ribonucleotide reductases (RNRs) and the MoaA enzyme involved in the biosynthesis of molybdopterin.

Open-shell singlet diradicaloid difluoreno[4,3-b:3′,4′-d]furan and its radical cation and dianion

We report difluoreno[4,3-b:3′,4′-d]furan derivative as a stable open-shell singlet diradicaloid.