Corsifurans A-C, 2-arylbenzofurans of presumed stilbenoid origin from Corsinia coriandrina (Hepaticae)

Enantioselective Construction of 2-Aryl-2,3-dihydrobenzofuran Scaffolds Using Cu/SPDO-Catalyzed [3 + 2] Cycloaddition

A new, efficient approach toward the preparation of 2-aryl-2,3-dihydrobenzofuran scaffolds through the Cu/SPDO-catalyzed [3 + 2] cycloaddition between quinone ester and styrene derivatives has been developed. The procedure features excellent enantioselectivities (up to 99% ee), high yields (up to 96%), and broad substrate tolerance. Additionally, asymmetric synthesis of natural corsifurans A and B from commercially available starting materials has also been achieved in two or three steps using this reaction as a key transformation.

Synthesis of Benzo[b]furans by Intramolecular C-O Bond Formation Using Iron and Copper Catalysis

One-pot processes for the synthesis of benzo[b]furans from 1-aryl- or 1-alkylketones using nonprecious transition metal catalysts have been developed. Regioselective iron(III)-catalyzed halogenation of the aryl ring, followed by iron- or copper-catalyzed O-arylation allowed the synthesis of various structural analogues, including the benzo[b]furan-derived natural products corsifuran C, moracin F, and caleprunin B.

Synthesis of Functionalized Indolines and Dihydrobenzofurans by Iron and Copper Catalyzed Aryl C-N and C-O Bond Formation

A simple and effective one-pot, two-step intramolecular aryl C-N and C-O bond forming process for the preparation of a wide range of benzo-fused heterocyclic scaffolds using iron and copper catalysis is described. Activated aryl rings were subjected to a highly regioselective, iron(III) triflimide-catalyzed iodination, followed by a copper(I)-catalyzed intramolecular N- or O-arylation step leading to indolines, dihydrobenzofurans, and six-membered analogues. The general applicability and functional group tolerance of this method were exemplified by the total synthesis of the neolignan natural product, (+)-obtusafuran. DFT calculations using Fukui functions were also performed, providing a molecular orbital rationale for the highly regioselective arene iodination process.

Chemical Constituents of Bryophytes: Structures and Biological Activity

Comparatively little attention has been paid to the bryophytes for use in the human diet or medicine in spite of the presence of 23 000 species globally. Several hundred new compounds have been isolated from the liverworts (Marchantiophyta), and more than 40 new carbon skeletons of terpenoids and aromatic compounds were found. Most of the liverworts studied elaborate characteristic odiferous, pungent, and bitter-tasting compounds, of which many show antimicrobial, antifungal, antiviral, allergic contact dermatitis, cytotoxic, insecticidal, anti-HIV, plant growth regulatory, neurotrophic, NO production and superoxide anion radical release inhibitory, muscle relaxing, antiobesity, piscicidal, and nematocidal activities. The biological effects ascribed to the liverworts are mainly due to lipophilic sesqui- and diterpenoids, phenolic compounds, and polyketides, which are the principal constituents of their oil bodies. Some mosses and liverworts produce significant levels of vitamin B₂ and tocopherols, as well as prostaglandin-like highly unsaturated fatty acids. The most characteristic chemical phenomenon of the liverworts is that most of the sesqui- and diterpenoids are enantiomers of those found in higher plants. In this review, the chemical constituents and potential medicinal uses of bryophytes are discussed.

Total synthesis of natural products containing benzofuran rings

In this review, various approaches for the construction of benzofurans as an important moiety in different natural products during the total synthesis of the natural of products are underscored.

Pungent and Bitter, Cytotoxic and Antiviral Terpenoids from Some Bryophytes and Inedible Fungi

Most liverworts elaborate characteristic odiferous, pungent and bitter tasting compounds many of which show antimicrobial, antifungal, antiviral, allergenic contact dermatitis, cytotoxic, insecticidal, anti-HIV, superoxide anion radical release, plant growth regulatory, neurotrophic, NO production inhibitory, muscle relaxant, antiobesity, piscicidal and nematocidal activities. Several inedible mushrooms produce female spider pheromones, strong antioxidant, and cytotoxic compounds. The present paper is concerned with the extraction and isolation of terpenoids from some bryophytes and inedible fungi and their pungent and bitter taste, and cytotoxic and antiviral activity.

Natural stilbenoids: distribution in the plant kingdom and chemotaxonomic interest in Vitaceae

Stilbenoids, a family of polyphenols known for the complexity of their structure and for their diverse biological activities, occur with a limited but heterogeneous distribution in the plant kingdom. The most prominent stilbene containing plant family, the Vitaceae, represented by the famous wine producing grape vines Vitis vinifera L., is one of the richest sources of novel stilbenes currently known, together with other families, such as Dipterocarpaceae, Gnetaceae and Fabaceae. This review focuses on the distribution of stilbenes and 2-arylbenzofuran derivatives in the plant kingdom, the chemical structure of stilbenes in the Vitaceae family and their taxonomic implication.

The diversity of Stemona stilbenoids as a result of storage and fungal infection

In relation to their biogenetic origin, 68 Stemona stilbenoids have been grouped into four structural types and are listed in order of increasing substitution pattern. Besides different hydroxylations and methoxylations, the rare C-methylations of the aromatic rings represent a typical chemical feature of these compounds. The formation of phenylbenzofurans constitutes another important chemical character separating Stemona species into two groups consistent with morphological and DNA data. Fungal infection leads to an increasing accumulation of stilbenes, dihydrostilbenes, and phenylbenzofurans with unsubstituted A-rings, suggesting the ecological role of these compounds as phytoalexins. Further oxygenations and methylations of both rings are interpreted as a result of aging or the drying processes. Bioautographic tests on TLC plates and germ-tube inhibition assays in microwells against four different fungi exhibited antifungal activities for almost all stilbenoids tested. Some derivatives also showed effects against yeasts and bacteria. Further activities may also be seen as dormancy-inducing factors of Stemona species occurring in periodically dry habitats. A leucotriene biosynthesis inhibition assay using 15 stilbenoids showed interesting structure-activity relationships, with more potent effects of some compounds than the commercial 5-lipoxygenase inhibitor zileuton being observed. Potential neuroprotective activities have been reported for three dihydrostilbene glucosides against 6-hydroxydopamine-induced neurotoxicity in human neuroblastoma SH-SY5Y cells.

New 2-arylbenzofurans from the root bark of Artocarpus lakoocha

Three new prenylated 2-arylbenzofurans – artolakoochol, 4-hydroxy-artolakoochol and cycloartolakoochol – have been isolated from the root bark of Artocarpus lakoocha Roxb., Their structures were elucidated through analysis of their spectroscopic data, and their antiherpetic potential was evaluated by the plaque reduction assay.

3-Ethyl-sulfanyl-2-(4-fluoro-phen-yl)-5-phenyl-1-benzofuran

In the title compound, C(22)H(17)FOS, the crystal studied was an inversion twin with a 0.42 (18):0.58 (18) domain ratio. The 4-fluoro-phenyl ring is rotated out of the benzofuran plane, making a dihedral angle of 17.82 (6)°, and the dihedral angle between the 5-phenyl ring and the benzofuran plane is 29.45 (7)°.

5-Bromo-2,7-dimethyl-3-methyl-sulfinyl-1-benzofuran

In the title compound, C(11)H(11)BrO(2)S, the O atom and the methyl group of the methyl-sulfinyl substituent are located on opposite sides of the plane of the benzofuran fragment. The crystal structure is stabilized by non-classical inter-molecular C-H⋯O hydrogen bonding, and by inter-molecular C-Br⋯π inter-actions, with C-Br⋯Cg = 3.629 Å (Cg is the centroid of the benzene ring). In addition, the crystal structure exhibits aromatic π-π interactions between the furan rings of neighbouring molecules [centroid-centroid distance = 4.206 (6) Å].

Volatiles released by a Streptomyces species isolated from the North Sea

The North Sea Streptomyces strain GWS-BW-H5 was investigated by analyzing headspace extracts of agar-plate cultures (HE) or liquid cultures (LCE), obtained with a closed-loop stripping apparatus (CLSA), by GC/MS (Table 1). The volatile profile of the HE is dominated by the known volatiles (-)-geosmin (4) and 2-methyisoborneol (1). Small amounts of sesquiterpenes occur, which are present in a more-diverse structural variety and in higher quantities in the LCE. The different structures can be rationalized by few cationic intermediates along their biosynthetic pathway. The most-prominent difference between the two culture methods were the presence of the Me-branched gamma- and delta-lactones 31-38, not previously reported from nature, in the LCE. Major components were 10-methyldodecan-5-olide (34), 10-methyldodec-2-en-4-olide (36), and 10-methyldodec-3-en-4-olide (38). The structures of all new lactones were verified by synthesis. Furthermore, more volatiles in higher amounts were produced by the liquid culture than by to the agar plate culture. Since 36 showed inhibitory growth effects against strain GWS-BW-H5, growth inhibition against twelve other strains isolated from the same habitat was tested. Antagonistic activity against four of the strains was observed, with a slightly higher threshold level than found for penicillin G, which was used in control experiments (Table 2).