Oxygen-containing Substituents Research Articles

Oxygen-Containing Quaternary Phosphonium Salts (oxy-QPSs): Synthesis, Properties, and Cellulose Dissolution.

In the present study, the synthesis of oxygen-containing quaternary phosphonium salts (oxy-QPSs) was described. Within this work, structure-property relationships of oxy-QPSs were estimated by systematic analysis of physical-chemical properties. The influence of the oxygen-containing substituent was examined by comparing the properties of oxy-QPSs in homology series as well as with phosphonium analog-included alkyl side chains. The crystal structure analysis showed that the oxygen introduction influences the conformation of the side chain of the oxy-QPS. It was found that oxy-QPSs, using an aprotic co-solvent, dimethylsulfoxide (DMSO), can dissolve microcrystalline cellulose. The cellulose dissolution in oxy-QPSs appeared to be dependent on the functional group in the cation and anion nature. For the selected conditions, dissolution of up to 5 wt% of cellulose was observed. The antimicrobial activity of oxy-QPSs under study was expected to be low. The biocompatibility of oxy-QPSs with fermentative microbes was tested on non-pathogenic Saccharomyces cerevisiae, Lactobacillus plantarum, and Bacillus subtilis. This reliably allows one to safely address the combined biomass destruction and enzyme hydrolysis processes in one pot.

Senkyunolide B exhibits broad-spectrum antifungal activity against plant and human pathogenic fungi via inhibiting spore germination and destroying the mature biofilm.

Aspergillus infection seriously jeopardize the health and safety of life of immunocompromised patients. The emergences of antifungal resistance highlight a demand to find new effective antifungal drugs. Angelica sinensis is a medicine-food herb and phthalides are its characteristic components. A few of phthalides have been reported to display satisfactory antifungal activities against plant pathogenic fungi. However, the structure activity relationships and antifungal action mechanism of phthalides remain to be further explored and elucidated. The antifungal activities of five natural phthalides and four artificial analogues were investigated, and their structure activity relationships were preliminarily elucidated in current study. The benzene ring moiety played an essential role in their antifungal activities; the oxygen-containing substituents on the benzene ring obviously impact their activities, the free hydroxyl was favorable to the activity. Typical phthalide senkyunolide B (SENB) exhibited broad antifungal activities against human and plant pathogenic fungi, especially, Aspergillus fumigatus. SENB affected the spore germination and hyphae growth of A. fumigatus via downregulating phosphatidylinositol-PKC-calcineurin axis and the expression of ENG genes. Moreover, SENB disturbed the oxidation-reduction process in A. fumigatus to destroy the mature biofilms. In vivo experiments indicated SENB significantly prolonged survival and decreased fungal burden in mouse model of invasive pulmonary aspergillosis. Phthalides could be considered as the valuable leads for the development of antifungal drug to cure plant and human disease. This article is protected by copyright. All rights reserved.

A New Concept of Enhancing the Anticancer Activity of Manganese Terpyridine Complex by Oxygen-Containing Substituent Modification.

Eleven manganese 4'-substituted-2,2':6',2″-terpyridine complexes (1a-1c and 2a-2h) with three non-oxygen-containing substituents (L1a-L1c: phenyl, naphthalen-2-yl and naphthalen-1-yl, L1a-L1c) and eight oxygen-containing substituents (L2a-L2h: 4-hydroxyl-phenyl, 3-hydroxyl-phenyl, 2-hydroxyl-phenyl, 4-methoxyl-phenyl, 4-carboxyl-phenyl, 4-(methylsulfonyl)phenyl, 4-nitrophenyl and furan-2-yl) were prepared and characterized by IR, elemental analysis or single crystal X-ray diffraction. In vitro data demonstrate that all of these show higher antiproliferative activities than cisplatin against five human carcinoma cell lines: A549, Bel-7402, Eca-109, HeLa and MCF-7. Compound 2d presents the strongest antiproliferative effect against A549 and HeLa cells, with IC50 values being 0.281 μM and 0.356 μM, respectively. The lowest IC50 values against Bel-7402 (0.523 μM) Eca-109 (0.514 μM) and MCF-7 (0.356 μM) were obtained for compounds 2h, 2g and 2c, respectively. Compound 2g with a nitro group showed the best results on the whole, with relevantly low IC50 values against all the tested tumor cells. The DNA interactions with these compounds were studied by circular dichroism spectroscopic and molecular modeling methods. Spectrophotometric results revealed that the compounds have strong affinities in binding with DNA as intercalators, and the binding induces DNA conformational transition. Molecular docking studies indicate that the binding is contributed by the π-π stacking and hydrogen bonds. The anticancer activities of the compounds are correlated with their DNA binding ability, and the modification of oxygen-containing substituents significantly enhanced the anticancer activity, which could provide a new rationale for the future design of terpyridine-based metal complexes with antitumor potential.

Stereoselective Epoxidation of Triterpenic Allylic Alcohols and Cytotoxicity Evaluation of Synthesized Compounds.

The epoxidation process of semi-synthetic triterpenoids 2-methyl-3-oxo-19β,28-epoxy- 18α-olean-1-ene, and its allylic alcohol derivatives were examined. 1,2α-epoxide, as the main product, was found to be formed from the starting enone exposed to m-chloroperbenzoic acid (mCPBA). In the case of hydroxy-directed mCPBA-oxidation of triterpenic allyl alcohols and their 3α-alkyl-substituted derivatives, inversion of C1 and C2 asymmetric centers with the formation of 1,2β-epoxyalcohols took place. The synthesis of 2,3α-epoxides was fulfilled from 2,3-dialkyl-substituted C(3) allyl alcohols by the action of pyridinium chlorochromate under [1,3]-oxidative rearrangement conditions. The transformations brought about enabled chiral oleanane derivatives with an oxygen-containing substituent at the C1, C2, and C3 atoms to be obtained. The study also provides information on in silico PASS prediction of pharmacological effects and in vitro evaluation of the cytotoxic activity of the synthesized compounds.

Structure-Activity Relationship and Evaluation of Phenethylamine and Tryptamine Derivatives for Affinity towards 5-Hydroxytryptamine Type 2A Receptor.

Among 14 subtypes of serotonin receptors (5-HTRs), 5-HT2AR plays important roles in drug addiction and various psychiatric disorders. Agonists for 5-HT2AR have been classified into three structural groups: phenethylamines, tryptamines, and ergolines. In this study, the structure-activity relationship (SAR) of phenethylamine and tryptamine derivatives for binding 5-HT2AR was determined. In addition, functional and regulatory evaluation of selected compounds was conducted for extracellular signal-regulated kinases (ERKs) and receptor endocytosis. SAR studies showed that phenethylamines possessed higher affinity to 5-HT2AR than tryptamines. In phenethylamines, two phenyl groups were attached to the carbon and nitrogen (R3) atoms of ethylamine, the backbone of phenethylamines. Alkyl or halogen groups on the phenyl ring attached to the β carbon exerted positive effects on the binding affinity when they were at para positions. Oxygen-containing groups attached to R3 exerted mixed influences depending on the position of their attachment. In tryptamine derivatives, tryptamine group was attached to the β carbon of ethylamine, and ally groups were attached to the nitrogen atom. Oxygen-containing substituents on large ring and alkyl substituents on the small ring of tryptamine groups exerted positive and negative influence on the affinity for 5-HT2AR, respectively. Ally groups attached to the nitrogen atom of ethylamine exerted negative influences. Functional and regulatory activities of the tested compounds correlated with their affinity for 5-HT2AR, suggesting their agonistic nature. In conclusion, this study provides information for designing novel ligands for 5-HT2AR, which can be used to control psychiatric disorders and drug abuse.

Review of Calixarene-Derivatives in Transition Metal Chemistry

The survey depicts the combination of large-scale monodentate phosphites in response to PCl3/NEt3 with p-tert-butyl calix[4]-(OH)3-OR, where R contains an oxygen-containing substituent (R = CH2P(O)Ph2, -CH2CO2Et, -CH2C(O)NEt2, -CH2CH2OMe). These funnel-shaped calissarenes have a phosphorus particle bridging three phenolic oxygen atoms, and are incredibly steady in NaOH-aqueous arrangement due to the cone point being more noteworthy than 180°. Upon response with transition metal particles, these phosphites shape either P monodentate complexes or expansive P,O chelate complexes including the oxygen atom of the R group. The reactivity of four different ligands in the rhodium-catalyzed hydroformylation of octene was examined. The general trend is that a bulkier phosphite ligand leads to a slower reaction rate. The ligand-to-base ratios ranged from 1.4 to 3.6, and the highest straight aldehyde selectivity was observed when the carboxylate group was CH2CO2Et.

Electrochemistry of Cobalta Bis(dicarbollide) Ions Substituted at Carbon Atoms with Hydrophilic Alkylhydroxy and Carboxy Groups

In this study we explore the effect on the electrochemical signals in aqueous buffers of the presence of hydrophilic alkylhydroxy and carboxy groups on the carbon atoms of cobalta bis(dicarbollide) ions. The oxygen-containing exo-skeletal substituents of cobalta bis(dicarbollide) ions belong to the perspective building blocks that are considered for bioconjugation. Carbon substitution provides wider versatility and applicability in terms of the flexibility of possible chemical pathways. However, until recently, the electrochemistry of compounds substituted only on boron atoms could be studied, due to the unavailability of carbon-substituted congeners. In the present study, electrochemistry in aqueous phosphate buffers is considered along with the dependence of electrochemical response on pH and concentration. The compounds used show electrochemical signals around −1.3 and +1.1 V of similar or slightly higher intensities than in the parent cobalta bis(dicarbollide) ion. The signals at positive electrochemical potential correspond to irreversible oxidation of the boron cage (the C2B9 building block) and at negative potential correspond to the reversible redox process of (CoIII/CoII) at the central atom. Although the first signal is typically sharp and its potential can be altered by a number of substituents, the second signal is complex and is composed of three overlapping peaks. This signal shows sigmoidal character at higher concentrations and may be used as a diagnostic tool for aggregation in solution. Surprisingly enough, the observed effects of the site of substitution (boron or carbon) and between individual groups on the electrochemical response were insignificant. Therefore, the substitutions would preserve promising properties of the parent cage for redox labelling, but would not allow for the further tuning of signal position in the electrochemical window.

Cyclopiazonic acid type indole alkaloids from Nicotiana tabacum-derived fungus Aspergillus versicolor and their anti-tobacco mosaic virus activities

Indole alkaloids have attracted widespread attention of chemists and biologists. Therefore, the aim of this study is to screen more bioactivities indole alkaloids from the microorganisms. In this study, five undescribed CPA-type indole alkaloids, aspergillines F–J, and three known CPA-type indole alkaloids, aspergilline A, aspergilline C, and cyclopiamide E, were obtained from the Nicotiana tabacum-derived fungus Aspergillus versicolor. Notably, aspergillines F and G represent the first examples of indole alkaloids with a benzo[cd]indol-2(1H)-one skeleton, and aspergilline J is also the firstly obtained indole alkaloids bearing a N-1-(2-(1H-imidazole-5-yl)ethyl) moiety. Aspergillines F–J and cyclopiamide E were tested for their anti-TMV activities, and the results revealed that aspergillines G and J exhibited obvious anti-TMV activities with inhibition rates of 41.2 and 56.8% at the concentration of 20 μM, respectively. These rates are high than that of positive control (with inhibition rate of 32.5%). In addition, the molecular docking studies for the isolated CPA-type indole alkaloids may also reveal that the benzo[cd]indol-2(1H)-one substructure is the fundamental for anti-TMV activity and the oxygen-containing substituent groups at C-19 also increases the inhibitory activity. This study of structure-activity relationship is helpful to find new anti-TMV activity inhibitors.

Vibrational Study (Raman, SERS, and IR) of Plant Gallnut Polyphenols Related to the Fabrication of Iron Gall Inks.

FT-Raman, FTIR, and SERS spectra of the structurally related gallnut polyphenols tannic acid, gallic acid, pyrogallol, and syringic acid are reported in this work aiming at performing a comparative assignation of the bands and finding specific marker features that can identify these compounds in complex polyphenol mixtures. Tannic and gallic acids are the principal components in oak gallnuts, and they can be found in iron gall inks. The different functional groups existing in these molecules and their spatial distribution lead to slight changes of the vibrations. The Raman spectra are dominated by bands corresponding to the ring vibrations, but the substituents in the ring strongly affect these vibrations. In contrast, the FTIR spectra of these molecules are dominated by the peripheral oxygen-containing substituents of the aromatic ring and afford complementary information. SERS spectroscopy can be used to analyze trace amounts of these compounds, but the spectra of these polyphenols show strong changes in comparison with the Raman spectra, indicating a strong interaction with the metal. The most significant modification observed in the SERS spectra of these compounds is the weakening of the benzene 8a ring vibration and the subsequent intensification of the 19a mode of the benzene ring. This mode is also more intense in the FTIR spectra, and its intensification in the SERS spectra could be related to a drastic change in the molecular polarizability associated with the interaction of the polyphenol with the metal in Ag NPs.

In silico design of new nitrogen-rich melamine-based porous polyamides applied to CO2/N2 separation

To improve the performance of nitrogen-rich melamine-based porous polyamides (MPPAs) for CO2 adsorption and separation, density functional theory and grand canonical Monte Carlo simulations were conducted to study the influence of the substitution position and functional groups. First, the fluorine atom was employed to assess the effect of the substitution position. The simulations revealed the best substitution position in the MPPA framework. Four oxygen-containing substituents were then introduced to further improve the CO2 selectively. The simulations revealed that sulfonic acid group modified MPPA has the greatest potential CO2 adsorption capacity and CO2/N2 selectivity.

Copolymerisation of 1-alkenes with bulky oxygen-containing olefins for dual-stage functionalisation of polyolefins

Pd–Diimine complexes catalyse the copolymerisation of 1-alkenes with olefins having a bulky oxygen-containing substituents, such as cyclic acetal or bicycloorthoester groups, affording the copolymers containing the comonomer unit up to 34%.

Reaction Mechanisms in Pyrolysis of Hardwood, Softwood, and Kraft Lignin Revealed by ReaxFF MD Simulations

Reactions of linkages and monomer rings in hardwood, softwood, and kraft lignin pyrolysis were investigated using reactive force field (ReaxFF) molecular dynamics (MD) simulations. Four large lignin models with diverse linkages and oxygen-containing groups were constructed on the basis of the two-dimensional lignin models proposed by Adler and Freudenberg for softwood lignin, by Nimz for hardwood lignin, and by Marton for kraft lignin. Large-scale ReaxFF MD simulations were performed using the GMD-Reax code and analyzed with the VARxMD code. The breaking of Cα/Cβ–O bonds in α/β–O–4 linkages is the dominant pathway to convert the source lignin molecules into smaller fragments. Differences in pyrolyzate evolution and linkage behavior among hardwood, softwood, and kraft lignin can be attributed to different reactions of linkages and their linked monomers induced by their varied oxygen-containing substituents. The consumption evolution of β–O–4 linkages can be promoted by their active substituents (Cα═O and Cα–O–4). The conversion of β–β_γ–O−α linkages and their linked monomer rings can be accelerated by the Cα═O substituent on the β–β_γ–O−α linkages and by the substituents of Cα–O–4 and OCH3 on the monomer ring. The different evolution profiles of the softwood, hardwood, and kraft lignin models are caused by the differences in the inherent structures (mainly linkage and oxygen-containing functional groups) of lignin from different tree species or isolation methods. Despite distinct differences in the pyrolyzate evolutions and linkage behaviors, the ring substructure evolutions of five- to seven-membered rings are similar for the four lignin models. This work demonstrates a useful alternative approach for investigating the pyrolysis reaction mechanism of lignin from varied sources.

Photoluminescence mechanism of phosphorene quantum dots (PQDs) produced by pulsed laser ablation in liquids

Phosphorene quantum dots (PQDs) with high photoluminescence (PL) quantum yield were fabricated through pulsed laser ablation of black phosphorus in liquids. The PL emission showed excitation wavelength-independent features due to the sufficient passivation by oxygen-containing substituents derived from the ablation-decomposed solvent molecules. There were four peaks in the PL profile showing a multifrequency PL effect, which provided a viable route to investigate the PL mechanism via the detailed structures of the PL profile. The two peaks at shorter wavelengths were attributed to the intrinsic PL transitions. The two peaks at longer wavelengths were assigned to the transitions from the lowest unoccupied molecular orbital to the two-surface states. The positions of the four peaks are redshifted with increasing solvent molecular chain length due to the passivation effect. The intense, excitation wavelength-independent, multifrequency and blue-violet PL emissions indicate the potential application in semiconductor light sources.

DFT study of Raman scattering spectra of complexes of spiropyrans with the silver cluster

The computational simulation of structure, energy and spectral characteristics of spiropyrans and their complexes with the cluster containing ten silver atoms was carried out using the density functional theory method (B3LYP/6-31G(d,p)/SDD). A competitive coordination of oxygen-containing substituents in the indoline and benzopyran moieties in spirocyclic molecules to the metal atoms was studied and an effect of position of donor groups on the activity of CO vibrational bands was established in the calculated Raman spectra. We revealed compounds, whose trans-trans-trans isomers upon a complexation with the silver cluster are characterized by the more than 100 times enhanced activity of band associated with the valence vibrations of CO bond in the Raman spectrum.

Effects of oxygen-containing substituents on pyrolysis characteristics of β-O-4 type model compounds

In order to uncover the influence of oxygen-containing functional groups on the pyrolysis characteristics of β-O-4 type model compounds, in-situ diffuse reflectance infrared pyrolysis and pyroprobe-GC–MS were used to study the migration patterns of functional groups and the specific pyrolysis product distributions with changing temperature. The results showed that the initial temperature of phenolic hydroxy production was 300°C, and peaks corresponding to this increased gradually in intensity in 1-benzyl-2-(2-methoxy-phenol)-ethanol, while this product did not begin appearing until 600°C in 1-ethyl-benzene-2-(2-methoxy-phenol). The intensities of the CH4 peaks were similar in all three samples, but the CO2 absorption peak was significantly lower in 1-(4-methoxy-phenoxy)-2-(2-methoxy-phenol)-ethanol. In addition, α-OH was found to promote the generation of aryl-ketone products. The 4-methoxy-styrene contents of 1-ethyl-benzene-2-(2-methoxy-phenol) and 1-(4-methoxy-phenoxy)-2-(2-methoxy-phenol)-ethanol at 500°C were 36.1% and 31.3%, respectively, higher than the styrene content of 1-benzyl-2-(2-methoxy-phenol)-ethanol (26.3%). The content of acetophenone was only 0.3% in 1-ethyl-benzene-2-(2-methoxy-phenol), but the yields of acetophenone and 4-methoxy-acetophenone were 16.7% and 19.6% in 1-benzyl-2-(2-methoxy-phenol)-ethanol and 1-(4-methoxy-phenoxy)-2-(2-methoxy-phenol)-ethanol, respectively.

ChemInform Abstract: Isolation and Synthesis of Polyoxygenated Dibenzofurans Possessing Biological Activity

AbstractReview: 45 refs.

Fungal polyketide engineering comes of age.

Natural products derived from fungi have a glorious pedigree in alleviating human suffering, with penicillins being the very first microbially derived compounds to be clinically used as antibiotics. Beyond the antibiotic activity of penicillins and contemporary cephalosporins, fungal natural products exhibit extensive utility in a myriad of clinical applications. Among these, fungal polyketides offer a vast array of bioactive molecules with prominent examples including the cholesterol-lowering lovastatin, immunosuppressant mycophenolic acid, and angiogenesis inhibitor cytochalasin E (1⇓–3). Although polyketide natural products possess a comparatively higher “hit rate” for drug development (0.3%) compared with synthetic high-throughput screening libraries (<0.001%) (4), their complicated chemical structures that contain multiple stereocenters and numerous oxygen-containing substituents complicate synthetic diversity-oriented modifications (5). This structural complexity has precipitated the need to expand the chemical space naturally explored in microbes through the genetic reprogramming of secondary metabolism to yield designer molecules. Engineering of natural products via coexpression of heterologous gene combinations has been realized for bacterial polyketide antibiotics (6, 7). In PNAS, Xu et al. (8) extend this paradigm for a class of fungal polyketide natural products called the …

Comparative Theoretical Studies on Energetic Ionic Salts Composed of Heterocycle-Functionalized Nitraminofurazanate-Based Anions and Triaminoguanidinium Cation

Density functional theory and volume-based thermodynamics calculations have been performed to study the crystal densities, heats of formation (HOFs), energetic properties, thermodynamics of formation, and impact sensitivity for the salts composed of heterocycle-functionalized nitraminofurazanate-based anions and triaminoguanidinium cation. The results show that the triaminoguanidinium nitraminofurazanate-based salts have high densities and positive HOFs. The substitution of the oxygen-containing substituent (−NO2 or −C(NO2)3) is helpful for enhancing the densities and detonation properties of the nitraminofurazanate-based salts, and the substitution of −C(NO2)3 exhibits the best performance. Incorporating the conjugated bridge −N═N– or −N═N–N═N– into the heterocycle-functionalized nitraminofurazanate-based salts is favorable for improving the density and detonation properties of its salt. The tetrazole-functionalized salts exhibit the best detonation properties among the three salt series. The calculated ...

Synthesis of azafluorenones and related compounds using deprotocupration–aroylation followed by intramolecular direct arylation

The efficiency of the deprotocupration–aroylation of 2-chloropyridine using lithiocuprates prepared from CuX (X=Cl, Br) and LiTMP (TMP=2,2,6,6-tetramethylpiperidido, 2 equiv) was investigated. CuCl was identified as a more suitable copper source than CuBr for this purpose. Different diaryl ketones bearing a halogen at the 2 position of one of the aryl groups were synthesized in this way from azines and thiophenes. These were then involved in palladium-catalyzed ring closure: substrates underwent expected CH-activation-type arylation to afford fluorenone-type compounds, and were also subjected to cyclization reactions leading to xanthones, notably in the presence of oxygen-containing substituents or reagents.

Debenzylation of Functionalized 4- and 5-Substituted 1,2,3-Triazoles

A range of 4- and 5-substituted N-benzyl-1,2,3-triazoles have been submitted to debenzylation using Pd/C and hydrogen in the presence of 1,1,2-trichloroethane. Triazoles with oxygen-containing substituents are efficiently debenzylated under these conditions. Triazoles with a phenyl or benzyl substituent on C4 or C5 are not debenzylated, whereas a pentyl-substituted derivative was readily debenzylated.