A short synthesis of oxazolidinone derivatives linezolid and eperezolid: A new class of antibacterials

Synthesis and structural analysis of a ZIF-9/GO composite for green catalytic C-C bond formation and N-formylation: a spectroscopic study

We report a new synthetic approach for a ZIF-9/GO composite material at room temperature and its comprehensive characterization using a variety of techniques, including PXRD, FT-IR, Raman, UV-vis, DRS, TGA, SEM, FE-SEM, EDX, TEM, ICP-MS, XPS, and BET. The material exhibited a moderate surface area and good thermal stability, as indicated by BET and TGA results. DRS revealed a band gap of 3.4 eV, which indicates slight semiconductor nature of the material. The crystalline nature of the ZIF-9/GO composite was confirmed by PXRD. The ZIF-9/GO composite exhibited excellent catalytic efficiency as a heterogeneous catalyst in Knoevenagel condensation and N-formylation, achieving yields of up to 98% under green reaction conditions with a wide range of substrate tolerance. The E-factor (0.10) and atom economy (91.7%) values were very close to ideal green chemistry parameters. In situ and UV-vis studies revealed reaction intermediates. The practical utility of this protocol was demonstrated by the gram scale synthesis of the value-added compounds 2-imino-2H-1-benzopyran-3-carbonitrile and paracetamol. Single-crystal XRD analysis of three of the compounds confirmed their structural integrity. The catalyst was easily separated via filtration and reused for up to six catalytic cycles without significant loss of activity, which is a crucial component of green synthesis, and hot-filtration experiments confirmed its heterogeneity. The probable mechanisms for both reactions are also well presented.

Photoinduced Direct Formylation of Anilines: Aerobic Oxidation Using an Odd Alternate Hydrocarbon Phenalenyl-Based Photocatalyst

We have introduced a sustainable approach for the photoinduced oxidative formylation of N,N-dimethylanilines using a phenalenyl-based photocatalyst. The methodology exhibits tolerance to a variety of electron-donating and -withdrawing groups as well as to diverse functional groups, specifically offering a selective and efficient pathway for the N-formylation. Using visible light, this photochemical technique proves to be an environmentally friendly, scalable, and milder alternative strategy. The mechanistic insights were gained through a series of spectroscopic techniques, including electron paramagnetic resonance, steady-state fluorescence, and fluorescence lifetime studies. Postfunctionalization was also completed and has the potential to be used in various applications.

Facile Synthesis of Oxazolidinones as Potential Antibacterial Agents

An efficient microwave-assisted synthesis route for novel oxazolidinone analogues has been developed. The general synthesis of these compounds began with an L-proline-mediated three-component Mannich reaction between commercially available 3-fluoro-4-morpholinoaniline, aqueous formaldehyde and α-hydroxyacetone. This was followed by a one-step cyclisation to form the core structure of oxazolidinone antibiotics which was subsequently derivatized. The novel compounds were evaluated for their antibacterial activity against M. smegmatis. One of the novel oxazolidinone derivatives 18 a1 produced a MIC of 8 mg/L, comparable with the commercial Rifampicin. The methodology is a useful addition to the field since it can make highly sought-after oxazolidinone derivatives, using cheaper, less harsh commercially available reagents, in a short time and one pot.

Manganese(II) and Zinc(II) metal complexes of novel bidentate formamide-based Schiff base ligand: synthesis, structural characterization, antioxidant, antibacterial, and in-silico molecular docking study

A new bidentate Schiff base ligand (C16H16Cl2N4), condensation product of ethylene diamine and 4-chloro N-phenyl formamide, and its metal complexes [M(C16H16Cl2N4)2(OAc)2] (where M = Mn(II) and Zn(II)) were synthesized and characterized using various analytical and spectral techniques, including high-resolution mass spectrometry (HRMS), elemental analysis, ultraviolet-visible (UV-vis), Fourier-transform infrared (FTIR) spectroscopy, AAS, molar conductance, 1H NMR, and powder XRD. All the compounds were non-electrolytes and nanocrystalline. The synthesized compounds were assessed for antioxidant potential by DPPH radical scavenging and FRAP assay, with BHT serving as the positive control. Inhibitory concentration at 50% inhibition (IC50) values were calculated and used for comparative analysis. Furthermore, the prepared compounds were screened for antibacterial activity against two Gram-negative bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-positive bacteria (Escherichia coli and Salmonella typhi) using disk-diffusion methods, with amikacin employed as the standard reference. The comparison of inhibition zones revealed that the complexes showed better antibacterial activity than the ligand. To gain insights into the molecular interactions underlying the antibacterial activity, the ligand and complexes were analyzed for their binding affinity with S. aureus tyrosyl-tRNA synthetase (PDB ID: 1JIL) and S. typhi cell membrane protein OmpF complex (PDB ID: 4KR4). These analyses revealed robust interactions, validating the observed antibacterial effects against the tested bacterial strains.

Aerobic Oxidative Synthesis of Formamides from Amines and Bioderived Formyl Surrogates

Herein we present a new strategy for the oxidative synthesis of formamides from various types of amines and bioderived formyl sources (DHA, GLA and GLCA) and molecular oxygen (O2) as oxidant on g-C3N4 supported Cu catalysts. Combined characterization data from EPR, XAFS, XRD and XPS revealed the formation of single CuN4 sites on supported Cuphen/C3N4 catalysts. EPR spin trapping experiments disclosed ⋅OOH radicals as reactive oxygen species and ⋅NR1R2 radicals being responsible for the initial C-C bond cleavage. Control experiments and DFT calculations showed that the successive C-C bond cleavage in DHA proceeds via a reaction mechanism co-mediated by ⋅NR1R2 and ⋅OOH radicals based on the well-equilibrated CuII and CuI cycle. Our catalyst has much higher activity (TOF) than those based on noble metals.

Microwave-Assisted Electrostatically Enhanced Phenol-Catalyzed Synthesis of Oxazolidinones

An electrostatically enhanced phenol is utilized as a straightforward, sustainable, and potent one-component organocatalyst for the atom-economic transformation of epoxides to oxazolidinones under microwave irradiation. Integrating a positively charged center into phenols over a modular one-step preparation gives rise to a bifunctional system with improved acidity and activity, competent in rapid assembly of epoxides and isocyanates under microwave irradiation in a short reaction time (20-60 min). A careful assessment of the efficacy of various positively charged phenols and anilines and the impact of several factors, such as catalyst loading, temperature, and the kind of nucleophile, on catalytic reactivity were examined. Under neat conditions, this one-component catalytic platform was exploited to prepare more than 40 examples of oxazolidinones from a variety of aryl- and alkyl-substituted epoxides and isocyanates within minutes, where up to 96% yield and high degree of selectivity were attained. DFT calculations to achieve reaction barriers for different catalytic routes were conducted to provide mechanistic understanding and corroborated the experimental findings in which concurrent epoxide ring-opening and isocyanate incorporation were proposed.

Synthesis of benzimidazolones via CO2 fixation and N-phenyl formamides using formic acid in presence of zinc embedded polymer complex

A merrifield supported heterogeneous zinc catalyst [Zn(Meri-Ald-Py)] was synthesized and applied for benzimidazolone synthesis through the fixation of carbon dioxide (CO₂) and for different N-formylated products synthesis under mild reaction conditions.

Synthesis of oxazolidinones: rhodium-catalyzed C-H amination of N-mesyloxycarbamates

N-Mesyloxycarbamates undergo intramolecular C-H amination reactions to afford oxazolidinones in good to excellent yields in the presence of rhodium(ii) carboxylate catalysts. The reaction is performed under green conditions and potassium carbonate is used, forming biodegradable potassium mesylate as a reaction by-product. This method enables the production of electron-rich, electron-deficient, aromatic and heteroaromatic oxazolidinones in good to excellent yields. Conformationally restricted cyclic secondary N-mesyloxycarbamates furnish cis-oxazolidinones in high yields and selectivity; DFT calculations are provided to account for the observed selectivity. trans-Oxazolidinones were prepared from acyclic secondary N-mesyloxycarbamates using Rh₂(oct)₄. The selectivity was reverted with a cytoxazone N-mesyloxycarbamate precursor using large chiral rhodium(ii) carboxylate complexes, affording the corresponding cis-oxazolidinone. This orthogonal selectivity was used to achieve the formal synthesis of (-)-cytoxazone.

An insight into the photophysical properties of amide hydrogen bonded N-(benzo[d]thiazol-2-yl) acetamide crystals

Three distinct, hydrogen bond associated N-(benzo[d]thiazol-2-yl) acetamides were synthesized by refluxing benzothiazoles with acetic acid. The nature of the assemblies was characteristic to the substituent in the benzothiazole moiety. In N-(benzo[d]thiazol-2-yl)acetamide, water acts as a bridge for forming three hydrogen bonds, as an acceptor to amide NH, and donors to carbonyl of amide and thiazole nitrogen assembles of three different N-(benzo[d]thiazol-2-yl)acetamide molecules. The N-(6-methylbenzo[d]thiazol-2-yl)acetamide formed a (amide) N-H…N (thiazole) bonded R²₂(8) molecular dimers by two homo-intermolecular hydrogen bonding interactions. N-(6-methoxybenzo[d]thiazol-2-yl)acetamide formed (amide)N-H…O (acid) & (acid)O-H…N (thiazole) interactions with the acetic acid, forming a R²₂(8) hydrogen-bonded ring by two hetero-intermolecular hydrogen bonding interactions.

First report on bio-catalytic N-formylation of amines using ethyl formate

A bio-catalyzed N-formylation reaction of different amines has been developed using ethyl formate as a formylating agent.

Linezolid: a promising option in the treatment of Gram-positives

Linezolid, an oxazolidinone antimicrobial agent that acts by inhibiting protein synthesis in a unique fashion, is used in the treatment of community-acquired pneumonia, skin and soft-tissue infections and other infections caused by Gram-positive bacteria including VRE and methicillin-resistant staphylococci. Currently, linezolid resistance among these pathogens remains low, commonly <1.0%, although the prevalence of antibiotic resistance is increasing in many countries. Therefore, the development of resistance by clinical isolates should prompt increased attention of clinical laboratories to routinely perform linezolid susceptibility testing for this important agent and should be taken into account when considering its therapeutic use. Considering the importance of linezolid in the treatment of infections caused by Gram-positive bacteria, this review was undertaken to optimize the clinical use of this antibiotic.

Advancement in methodologies for reduction of nitroarenes

Recent advancement in reduction methods of nitroarenes are reviewed. The different methods are classified based on the source of hydrogen utilized during reduction and the mechanism involved in the reduction process.

Structures of cycloserine and 2-oxazolidinone probed by X-ray photoelectron spectroscopy: theory and experiment

The electronic structures and properties of 2-oxazolidinone and the related compound cycloserine (CS) have been investigated using theoretical calculations and core and valence photoelectron spectroscopy. Isomerization of the central oxazolidine heterocycle and the addition of an amino group yield cycloserine. Theory correctly predicts the C, N, and O 1s core spectra, and additionally, we report theoretical natural bond orbital (NBO) charges. The valence ionization energies are also in agreement with theory and previous measurements. Although the lowest binding energy part of the spectra of the two compounds shows superficial similarities, further analysis of the charge densities of the frontier orbitals indicates substantial reorganization of the wave functions as a result of isomerization. The highest occupied molecular orbital (HOMO) of CS shows leading carbonyl π character with contributions from other heavy (non-H) atoms in the molecule, while the HOMO of 2-oxazolidinone (OX2) has leading nitrogen, carbon, and oxygen pπ characters. The present study further theoretically predicts bond resonance effects of the compounds, evidence for which is provided by our experimental measurements and published crystallographic data.

(3R,3aR,6R,6aR)-Hexa-hydro-furo[3,2-b]furan-3,6-diyl dibenzoate

The title compound, C₂₀H₁₈O₆, prepared from d-mannitol by a two-step procedure, is a functionalized fused bis-tetra­hydro­furan. In the central fragment, consisting of two fused tetra­hydro­furan rings, one O atom and its two adjacent C atoms, a methyl­ene and a bridgehead C atom, are disordered over two sets of sites with an occupancy ratio of 0.735 (9):0.265 (9). In the major component, the ring containing the disordered O atom is a half-chair conformation with twisted methylene and benzoate-substituted C atoms, whereas the other ring has a half-chair or T-form conformation. In the minor component, the ring with the disordered O atom has an envelope conformation, with the O atom as the flap, and the other ring has a half-chair conformation, with the O atom and the other bridgehead CH atom being twisted. The two aromatic rings are inclined to one another by 20.00 (12)°. In the crystal, adjacent molecules are linked via C—H⋯π interactions, forming chains propagating along [010].

(3S,3aS,6R,6aR)-2-Oxohexa-hydro-furo[3,2-b]furan-3,6-diyl dibenzoate

The title compound, C₂₀H₁₆O₇, contains a cis-fused γ-lactone tetra­hydro­furan ring system functionalized with two benzo­yloxy groups. Both rings adopt an envelope conformation. The mol­ecule assumes an elongated shape and exibits non-crystallographic C₂ symmetry. The benzo­yloxy groups are almost planar [maximum deviations of 0.0491 (15) and 0.0336 (17) Å for the O atoms] and their mean planes are inclined to one another by 16.51 (4)°. The crystal packing features weak C—H⋯O inter­actions. The aryl groups of adjacent mol­ecules are parallel shifted with face-to-face contacts and a shortest inter­molecular C⋯C distance of 3.482 (4) Å.

Bioresolution of (R)-glycidyl azide by Aspergillus niger ZJUTZQ208: a new and concise synthon for chiral vicinal amino alcohols

A newly isolated Aspergillus niger strain containing epoxide hydrolase was used to resolve racemic glycidyl azide and four derivatives to the (R)-enantiomers. After optimization of the biotransformation conditions, (R)-glycidyl azide was produced with good enantioselectivity (e.e.s > 95 %, E > 20). The substrate structure, pH, and reaction time were found to have profound influences on the catalytic property of A. niger ZJUTZQ208. Enantiopure glycidyl azide was further utilized to synthesize linezolid in good yield, indicating it is a new and concise synthon for chiral vicinal amino alcohols. Enzyme-substrate docking studies were carried out with glycidyl azide to study the selectivity of this strain.

Formylation of amines and alcohols using aminopropylated mesoporous SBA-15 silica (APMS) as an efficient and recyclable catalyst

Aminopropylated mesoporous SBA-15 silica (APMS) is introduced as a new, recyclable and efficient catalyst for the formylation of a variety of amines and alcohols by using readily available formic acid under solvent-free conditions.

[Carbohydrate study for 40 years]

This review describes the carbohydrate study and the natural product related to the glycoside chemistry. What shall the people in the field of pharmacognosy and natural products chemistry search in scene in future? Forty years before while isolating dimeric compound having naphthoquinonepyrone skeleton from the coloring material produced by the pathogen that hosted in wheat and caused rotten root disease, silica gel has to be treated with oxalic acid to reduce the absorbency before separation. However now a days, availability of reversed phase adsorbents for liquid chromatography has made the separation and isolation of complex compounds possible, easy and rapid. With the advancement of mechanical/physicochemical analytic methods, it has even been possible to isolate traces of compounds present in complex. This advancement has made it possible to determine structure of saponins and complex polysaccharides without decomposition and carry out in vitro bioassay at the same time using various cells on-line. Further, this review describes the oligosaccharide syntheses and biological activities of glycosphingolipids, focusing especially on those found in invertebrates.