An alternative total synthesis of diplodialide-B

In this paper, an enantioselective synthesis of diplodialide-B has been described. To accomplish this target, a combination of regioselective ring opening of the chiral epoxide, Jacobsen hydrolytic kinetic resolution and Yamaguchi macrolactonization were used as the key steps.     

Novel heterocyclic 1,3,4-oxadiazole derivatives of fluoroquinolones as a potent antibacterial agent: Synthesis and computational molecular modeling

Design and synthesis of novel series of 1,3,4-oxadiazoles containing FQs derivatives and screened their antibacterial, antimycobacterial properties. The synthesized compounds were characterized by different spectral techniques like IR, ¹H NMR, ¹³C NMR, mass and elemental analysis. The results of the antimicrobial activity and compounds 6d, 6b, 6e, 6f and 6a demonstrated potent antibacterial activities with zone of inhibition of 42, 36, 37, 34 and 30 mm against S. aureus, E. faecalis, S. pneumoniae, E. coli and K. pneumoniae, respectively. 1,3,4-Oxadiazole derivatives 6a, 6b, 6 g were showed excellent antimycobacterial activity against M. smegmatis H₃₇Rv with MICs 22.35, 16.20, 20.28 µg/mL, respectively. FQs 6d and 6b exhibited highest hydrogen bonding interactions with Asp83 (3.11 A?), Ser80 (2.15 A?) Asp27 (σ-σ), Arg87 (Π-Π), Arg87 (Π-Π), Ser80 (σ-σ), Ala84 (σ-σ) and binding energies ΔG?=????6.41, ??6.97 kcal/mol with active site of topoisomerase-IV from S. pneumoniae [4KPE]. We performed a computational investigation of compounds 6a–j for their absorption, distribution, metabolism and excretion (ADME) properties by using the Molinspiration, Molsoft toolkits. The ligands 6f, 6d and 6b reveal the highest pharmacokinetic properties and possess maximum drug-likeness model score 1.59, 1.46 and 1.23, respectively.

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Syntheses and structures of nickel(II) and copper(II) complexes with biacetyl bis(benzoylhydrazone): one-dimensional self-assembly via π–π interaction and hydrogen bonding

Reactions of Ni(O₂CCH₃)₂·4H₂O and Cu(O₂CCH₃)₂·H₂O with biacetyl bis(benzoylhydrazone) (H₂babh) in alcoholic media afford mononuclear nickel(II) and copper(II) complexes of general formula [M(babh)]. The complexes have been characterized by microanalysis (C, H, N), magnetic susceptibility, and various spectroscopic measurements. X-ray structures of both complexes have been determined. The metal centre in [Ni(babh)] is in square-planar N₂O₂ environment provided by the tetradentate babh²⁻. On the other hand, [Cu(babh)] crystallizes as distorted square-pyramidal [Cu(babh)(CH₃OH)] from methanol. Here the tetradentate babh²⁻ constitutes the N₂O₂ square-base and the O-coordinating methanol occupies the apical site. In the crystal lattice, the molecules of [Ni(babh)] form a one-dimensional π-stacked structure. The [Cu(babh)(CH₃OH)] molecules also form a one-dimensional structure with alternating long and short Cu···Cu distances via intermolecular O–H···N hydrogen bonding and π–π interaction.     

Duality for Semi-Infinite Minimax Fractional Programming Problem Involving Higher-Order (Φ, ρ)-V-Invexity

In this paper, we introduce the concept of higher-order (Φ, ρ)-V-invexity and present two types of higher-order dual models for a semi-infinite minimax fractional programming problem. Weak, strong, and strict converse duality theorems are discussed under the assumptions of higher-order (Φ, ρ)-V-invexity to establish a relation between the primal and dual problems.     

Metal free montmorillonite KSF clay catalyzed practical synthesis of benzoxazoles and benzothiazoles under aerobic conditions

An efficient method for the synthesis of benzoxazoles and benzothiazoles via montmorillonite KSF clay catalyzed condensation reaction between 2-aminophenols or 2-aminothiophenols and β-diketones is reported. The efficiency of the reaction reflects from the wide substrate scope with electronic differentiation on aryls. The reaction is metal free and proceeds without the exclusion of air or moisture, and further the catalyst can be recycled up to 3–5 catalytic cycles.     

Synthesis and Biological Evaluation of New Ibuprofen‐1,3,4‐oxadiazole‐1,2,3‐triazole Hybrids

A new hybrid polydentate template comprising distinctive pharmacophoric groups, namely, ibuprofen, 1,3,4‐oxadiazole, and 1,2,3‐triazole linked through a thioether bridge was achieved by one‐pot synthesis by exploring multicomponent Cu‐catalyzed “click chemistry” approach. The target structures were characterized by NMR, IR, and LC‐Mass. The X‐ray analysis of 2‐(1‐(4‐isobutylphenyl)ethyl)‐5‐(((1‐(3‐nitrophenyl)‐1H‐1,2,3‐triazol‐4‐yl)methyl)thio)‐1,3,4‐oxadiazole ( 8a ) confirmed the assigned structure. The in vitro antibacterial and anticancer activity of these compounds revealed that 2‐(1‐(4‐isobutylphenyl)ethyl)‐5‐(((1‐phenyl‐1H‐1,2,3‐triazol‐4‐yl)methyl)thio)‐1,3,4‐oxadiazole ( 8b ) demonstrated more potent antibacterial activity against Gram‐negative strains (Escherichia coli and Pseudomonas aeruginosa) and 2‐(((1‐(2,4‐dimethylphenyl)‐1H‐1,2,3‐triazol‐4‐yl)methyl)thio)‐5‐(1‐(4 isobutylphenyl)ethyl)‐1,3,4‐oxadiazole ( 8e ) exhibited anticancer activity with IC₅₀ of 27.50 and 31.03 μg/mL against HeLa and MCF‐7 cell lines, respectively.     

Stereoselective Total Synthesis of Mangiferaelactone using D‐Mannose as a Chiral Pool

A convergent total synthesis of mangiferaelactone has been accomplished in a highly stereoselective manner from readily available D ‐mannose. The following methods like organocatalytic enantioselective epoxidation, ring‐closing metathesis, and Steglich esterification have been employed as key steps, which make this approach more attractive.     

Primes in sumsets

We obtain an upper bound for the number of pairs \( (a,b) \in {A\times B} \) such that \( a+b \) is a prime number, where \( A, B \subseteq \{1,\ldots ,N \}\) with \(|A||B| \, \gg \frac{N^2}{(\log {N})^2}\), \(\, N \ge 1\) an integer. This improves on a bound given by Balog, Rivat, and Sárközy.     

Tandem One Pot and Efficient Method for the Palladium‐Reagent‐Catalyzed Cross‐Coupling of Quinazoline Thiols

A facile synthesis of 1,4‐dihydroquinazolines from 2‐aminobenzyl amine and carbon disulfide via dithiocarbamate performed at room temperature is reported. Corresponding S‐alkyl quinazoline derivatives were obtained from 1,4‐dihydroquinazolines in one‐pot reactions under the palladium reagents after addition of alkyl halides. The versatility of this synthetic protocol has been demonstrated with various halo benzenes. The products thus obtained have been characterized by MP, IR, ¹H‐NMR, and mass spectroscopy.