Phenol Skeleton Research Articles

Chiral Phenol‐2NO Ligand Cooperation with Achiral Organic Base in the Zn(II)‐Catalyzed Asymmetric Alkylation Reaction of Indoles

Comprehensive SummaryThe privileged C2‐symmetric rigid phenol‐type ligand is more attractive but challenging in asymmetric catalysis. Herein, we designed and synthesized a class of rigid‐featured chiral tridentate Phenol‐2NO ligands, that incorporate the advantages of both the phenol skeleton and pyrroloimidazolone‐based N‐oxide moiety, from readily available L‐prolinamides in operationally simple two steps and up to 44% overall yield. More importantly, using an achiral quinoline derivative as an additive, the newly developed Phenol‐2NO ligand could serve as the anioic ligand upon deprotonative activation to coordinate to Zn(II) to form a highly enantioselective catalyst for the asymmetric Michael‐type Friedel‐Crafts alkylation reaction of indoles with 2,3‐dioxopyrrolidines. Excellent yields (up to 90%) and high enantioselectivities (up to 99% ee) are obtained for a wide range of substrates under mild conditions. Experiments and DFT calculations revealed the reaction mechanism and the origins of the enantioselectivity. This also represented the first activation of phenol‐type ligand/metal complex by an achiral organic base as the additive in asymmetric catalysis.

Incorporation of phenolic skeleton into imidazolium ionic polymers as recyclable catalysts for efficient fixation of CO2 into cyclic carbonates

Developing a greener and efficient catalysts towards the direct fixation of atmospheric CO2 and then being used to synthesize high-value chemicals is of great interest, but challenging. To achieve this aim, rational design of the catalyst is very important. Herein, three imidazolium-based ionic polymers (IPs), named as IP 1–IP 3, are straightforwardly synthesized through a simple one-pot quaternization method by employing benzyl chloride linkers and tri-imidazole monomers (L1 and L2). These IPs are fully characterized using FTIR spectroscopy, 13C MAS NMR, XRD, elemental analysis, SEM with elemental mapping, HRTEM, TGA, XPS spectroscopy, nitrogen adsorption–desorption, and CO2/NH3-TPD methods. The newly synthesized IP 1 catalyst with phenolic hydroxyl shows an excellent catalytic activity toward CO2 cycloaddition with 97.1 % yield of cyclic carbonate under mild conditions (80 °C, 0.1 MPa CO2, solvent-free, 4.5 h). Moreover, the IP 1 catalyst is highly robust and can be reused at least for 7 consecutive runs. Mechanistic studies indicate that the synergic effect of hydrogen bonding and halogen anion in the IP 1 catalyst afford the ability to activate the substrate and ease the reaction kinetics, which results in an enhanced catalytic efficiency toward CO2 fixation. This work provides an efficient new method for the design and synthesis of multifunctional heterogeneous catalysts for the CO2 cycloaddition reaction.

Thermosensitive visible-light-excited visible-/NIR-luminescent complexes with lanthanide sensitized by the π-electronic system through intramolecular H-bonding.

Visible-luminescent lanthanide (LnL) complexes with a highly planar tetradentate ligand were successfully developed for a visible-light solid-state excitation system. L was designed by using two 2-hydroxy-3-(2-pyridinyl)-benzaldehyde molecules bridged by ethylenediamine, which was then coordinated to a series of Ln ions (Ln = Nd, Sm, Eu, Gd, Tb, Dy, and Yb). From the measurement of single-crystal X-ray analysis of EuL, two phenolic O atoms and two imine N atoms in L were coordinated to the Eu ion, and each π-electronic system took coplanar with the edged-pyridine moiety through an intramolecular hydrogen bond. The enol group on the phenolic skeleton changed to the keto form, and the pyridine was protonated. Thus, intramolecular proton transfer occurred in L after the complexation. Other complexes take isostructure. The space group is P-1, and the c-axis shrinks with decreasing temperature without a phase transition in EuL. The yellow color caused by the planar structure of L can sensitize ff emission by visible light, and the luminescence color of each complex depends on central Ln ions. Furthermore, a phosphorescence band also appeared at rt with ff emission in LnL. Drastic temperature dependence of luminescence was clarified quantitatively.

Synthesis of polysubstituted phenols via [3+3] condensation reaction from tricarbonyl compounds and readily available enaminones, cinnamaldehydes or arylformyl trifluoroacetones

An intermolecular [3 + 3] condensation reaction to synthesize polysubstituted phenols from tricarbonyl compounds and readily available enaminones has been developed. Replacing enaminones with cinnamaldehydes or benzoyl trifluoroacetones, we can also obtain similar polysubstituted phenol skeleton, which enriches the method of these compounds.

Chain Breaking Antioxidant Activity of Heavy (S, Se, Te) Chalcogens Substituted Polyphenols.

Polyphenols are probably the most important family of natural and synthetic chain-breaking antioxidants. Since long ago, chemists have studied how structural (bioinspired) modifications can improve the antioxidant activity of these compounds in terms of reaction rate with radical reactive oxygen species (ROS), catalytic character, multi-defence action, hydrophilicity/lipophilicity, biodistribution etc. In this framework, we will discuss the effect played on the overall antioxidant profile by the insertion of heavy chalcogens (S, Se and Te) in the phenolic skeleton.

Bioconversion of Phenolic Monomers of Lignin and Lignin-Containing Substrates by the Basidiomycete Lentinus tigrinus

The bioconversion of phenolic monomers of lignin (veratrol, vanillin, and vanillyl alcohol), hydrolyzed lignin, and sodium lignosulfonate (a product of the chemical modification of native lignin) by the basidiomycete Lentinus tigrinus was studied. It was found that the growth of the fungi on lignin monomer compounds is suppressed. A noticeable growth of the fungal biomass was observed only on the technical substrate sodium lignosulfonate. A comprehensive physicochemical study of the products of microbial transformation of sodium lignosulfonate was performed. It was established that the main direction of lignin bioconversion is oxidative condensation to form humic substances. In this case, depolymerization of the phenolic skeleton of lignin to monomeric phenol derivatives did not occur. The aromatic carbon atoms of the phenolic skeleton, unlike the carbon atoms of polysaccharides, were not involved in the fungal biomass growth. The observed growth of the fungus on the technical substrate sodium lignosulfonate can be explained by the presence of admixtures of oligomeric polysaccharides hemicellulose and cellulose, which can be used by the fungus as a carbon source.

The position of prenylation of isoflavonoids and stilbenoids from legumes (Fabaceae) modulates the antimicrobial activity against Gram positive pathogens.

The legume plant family (Fabaceae) is a potential source of antimicrobial phytochemicals. Molecular diversity in phytochemicals of legume extracts was enhanced by germination and fungal elicitation of seven legume species, as established by RP-UHPLC-UV-MS. The relationship between phytochemical composition, including different types of skeletons and substitutions, and antibacterial properties of extracts was investigated. Extracts rich in prenylated isoflavonoids and stilbenoids showed potent antibacterial activity against Listeria monocytogenes and methicillin-resistant Staphylococcus aureus at concentrations between 0.05 and 0.1% (w/v). Prenylated phenolic compounds were significantly (p<0.01) correlated with the antibacterial properties of the extracts. Furthermore, the position of the prenyl group within the phenolic skeleton also influenced the antibacterial activity. Overall, prenylated phenolics from legume seedlings can serve multiple purposes, e.g. as phytoestrogens they can provide health benefits and as natural antimicrobials they offer preservation of foods.

Toxicities of active constituent isolated from Thymus vulgaris flowers and its structural derivatives against Tribolium castaneum (Herbst)

Insecticidal activity of 2-isopropyl-5-methylphenol isolated from Thymus vulgaris oil and its derivatives against Tribolium castaneum adults and larvae were evaluated using contact and fumigant bioassays. To elucidate the structure–activity relationship, 2-isopropyl-5-methylphenol and its derivatives were determined. Based on the LD50 values, 2-isopropylphenol was most toxic to T. castaneum adults and larvae, followed by 4-isopropylphenol, 2-methylphenol, 3-methylphenol, and phenol in contact and fumigant bioassays. These results indicate that the introduction of a functional group such as methyl and isopropyl group into the phenol skeleton has an important influence on contact and fumigant toxicities. Furthermore, 2-isopropyl-5-methylphenol and its derivatives could be used as an alternative to control stored-grain insects.

Fate of Carbohydrates and Lignin during Composting and Mycelium Growth of Agaricus bisporus on Wheat Straw Based Compost.

In wheat straw based composting, enabling growth of Agaricus bisporus mushrooms, it is unknown to which extent the carbohydrate-lignin matrix changes and how much is metabolized. In this paper we report yields and remaining structures of the major components. During the Phase II of composting 50% of both xylan and cellulose were metabolized by microbial activity, while lignin structures were unaltered. During A. bisporus’ mycelium growth (Phase III) carbohydrates were only slightly consumed and xylan was found to be partially degraded. At the same time, lignin was metabolized for 45% based on pyrolysis GC/MS. Remaining lignin was found to be modified by an increase in the ratio of syringyl (S) to guaiacyl (G) units from 0.5 to 0.7 during mycelium growth, while fewer decorations on the phenolic skeleton of both S and G units remained.

Isolation of Insecticidal Constituent from Ruta graveolens and Structure-Activity Relationship Studies against Stored-Food Pests (Coleoptera)

Isolates from essential oil extracted from the flowers and leaves of Ruta graveolens and commercial phenolic analogs were evaluated using fumigant and contact toxicity bioassays against adults of the stored-food pests Sitophilus zeamais, Sitophilus oryzae, and Lasioderma serricorne. The insecticidal activity of these compounds was then compared with that of the synthetic insecticide dichlorvos. To investigate the structure-activity relationships, the activity of 2-isopropyl-5-methylphenol and its analogs was examined against these stored-food pests. Based on the 50% lethal dose, the most toxic compound against S. zeamais was 3-isopropylephenol, followed by 2-isopropylphenol, 4-isopropylphenol, 5-isopropyl-2-methylphenol, 2-isopropyl-5-methylphenol, 3-methylphenol, and 2-methylphenol. Similar results were observed with phenolic compounds against S. oryzae. However, when 2-isopropyl-5-methylphenol isolated from R. graveolens oil and its structurally related analogs were used against L. serricorne, little or no insecticidal activity was found regardless of bioassay. These results indicate that introducing and changing the positions of functional groups in the phenol skeleton have an important effect on insecticidal activity of these compounds against stored-food pests.

Predicting structural change of lignin macromolecules before and after heat treatment using the pyrolysis-GC/MS technique

Milled wood lignin extracted from poplar wood was subjected to a heat treatment in the temperature range of 150–300°C at 50°C intervals. The results of several chemical characterizations (proton nuclear magnetic resonance (1H NMR), derivatization followed by reductive cleavage (DFRC), elemental composition) and thermogravimetric analysis revealed that cleavage of the β-O-4 linkage accompanied by condensation and a charring reaction occurred during the heat treatment, leading to the formation of a thermally stabilized lignin at 300°C (300-L) with enrichment of the condensed carbon–carbon bond. Pyrolysis-GC/MS data showed that 41 kinds of pyrolysis products, mainly composed of monomeric phenols, were released from the heat-treated lignin, and the yield of such products was significantly dependent on the lignin sample and the pyrolysis temperature. The maximum yield of total pyrolysis products from 300-L was obtained at a pyrolysis temperature of 600°C, whereas the maximum yield from the other samples was observed at 500°C due to the high thermal stability and degree of condensation of 300-L. Moreover, the pyrolysis-GC/MS results suggested that the side chain in the phenol skeleton (C3C6) was considerably degraded at 300°C, resulting in the accumulation of a C6/C1C6/C2C6-type lignin structure in the 300-L sample. With an increase in the pyrolysis temperature, the syringyl/guaiacyl (S/G) ratio of all lignin samples, as determined from the pyrolysis products, constantly decreased due to an increase in G-type compounds released in the high temperature region.

Total synthesis of gibbilimbols A-D.

Gibbilimbols A-D (1-4) were synthesized in 32-49% yield over four steps from commercially available starting materials. A copper-catalyzed coupling of 4-methoxyphenylmagnesium bromide with various unsaturated alkyl bromides was the key step in assembling the (long-chain alkyl)phenol skeleton.

Biossensores amperométricos para determinação de compostos fenólicos em amostras de interesse ambiental

Phenols are widely used in many areas and commonly found as industrial by-products. A great number of agricultural and industrial activities realise phenolic compounds in the environmental. Waste phenols are produced mainly by the wood-pulp industry and during production of synthetic polymers, drugs, plastics, dyes, pesticides and others. Phenols are also released into the environmental by the degradation of pesticides with phenolic skeleton. The phenols level control is very important for the environmental protection. Amperometric biosensor has shown the feasibility to complement laboratory-based analytical methods for the determination of phenolic compounds, providing alternatives to conventional methods which have many disadvantages. This brief review considers the evolution of an approach to amperometric measurement using the catalytic properties of some enzymes for phenolic compounds monitoring.

Sample preparation in the determination of phenolic compounds in fruits

Phenolic compounds occur as secondary metabolites in all plants.1 They embrace a considerable range of substances possessing an aromatic ring bearing one or more hydroxy substituents, although a more precise definition is based on metabolic origin as those substances derived from the shikimate pathway and phenylpropanoid metabolism.2 A convenient classification of the plant phenols distinguishes the number of constitutive carbon atoms in conjunction with the structure of the basic phenolic skeleton (Table 1). The range of known phenolics is thus vast and also includes polymeric lignins and condensed tannins. Some plant phenols may be involved in primary metabolism whereas others have an effect on plant growth or protect the more vulnerable cell constituents against photooxidation by ultraviolet light by virtue of their strong UV absorption.3 Plant phenols also play an important role in disease resistance in the plant. Intense interest in fruit phenolics is also related to their physiological activity which depends on their antioxidant activity, the ability to scavenge both active oxygen species and electrophiles, the ability to inhibit nitrosation and to chelate metal ions, the potential for autooxidation and the capability to modulate certain cellular enzyme activities.4–7 Thus, knowledge of the levels of these compounds in plants is of considerable interest but is limited by problems of analysis. The structural diversity of the phenolics and its effect on physicochemical behaviour such as solubility and analyte recovery presents a challenging analytical problem. Moreover, a number of phenolic compounds are easily hydrolysed and many are relatively easily oxidized, which further complicates sample handling.8,9 This review emphasises the importance of sample preparation in the determination of phenolic compounds in plant materials particularly fruits. Fruits are an important dietary source of phenolic substances although interest is also shifting to other parts of the plant as potential commercial sources of phenols. Sample preparation is a critical step in analysis and this is even more significant with real samples where the matrix components are biologically active and the analytes represent a diverse spectrum of numerous compounds, many having an unknown identity. Thus, methods of extraction of phenols from fruits are generally dependent on several factors while the usual quantification procedures involve the separation sciences and are universally applicable. Soleas et al.10 illustrated this point. They developed a derivatization procedure for determination of 15 phenolic constituents in solid vitaceous plant materials and concluded that the method ‘should be suitable to measure polyphenols in fruit, vegetables, and other foods provided that efficient extraction techniques are employed’. Such statements are seen frequently in the analytical literature but they tend to belittle the importance of this step (or perhaps they serve to underline its critical importance). Rhodes and Price11 observed that the determination of phenolic species in foods is an important outstanding problem and reviewed methods for the extraction and purification of phenolic antioxidants as the conjugated forms that exist in plant foods. Knowledge of the extraction of phenolics is also desirable outside the analytical context for it has important practical applications in the food industry. For instance, the mechanism and kinetics of phenolic extraction from wood to wine during ageing in barrels12 has significant consequences for the production of quality wines.

ChemInform Abstract: ADAMANTANAMINE DERIVATIVES. ANTIMICROBIAL ACTIVITIES OF CERTAIN MANNICH BASES

AbstractDurch Mannichreaktion werden verschiedene substituierte Adamantanderivate, z.B. (I) und (11)) hergestellt.

Adamantanamine derivatives. Antimicrobial activities of certain Mannich bases

A series of Mannich condensation products containing the beta-(1-adamantylamino)propiophenone skeleton (type I) and the o-(1-adamantylaminomethyl)phenol skeleton (type II) was synthesized and tested for antimicrobial activity against certain bacteria and fungi by the agar diffusion and tube dilution methods. Type I compounds were more active than type II compounds and had a broad-spectrum effect on certain gram-negative and gram-positive bacteria, acid-fast bacteria, a yeast, and a mold.