2,4,4,6-Tetrabromo-2,5-cyclohexadienone (TABCO), N-Bromosuccinimide (NBS) and Bromine as Efficient Catalysts for Dithioacetalization and Oxathioacetalization of Carbonyl Compounds and Transdithioacetalization Reactions

The use of 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TABCO), N-bromosuccinimide (NBS), and bromine as efficient catalysts for conversion of carbonyl compounds to their cyclic and acyclic dithioacetals and 1,3-oxathiolanes under mild reaction conditions are described. These catalysts are also used for efficient transdithioacetalization of acetals, diacetals, ketals, acylals, enamines, hydrazones, and oximes with high yields in the presence of thiols.     

The response of selected isomers of B80 buckyball toward NH3 adsorption: a density functional theory investigation

Density functional theory calculations at the B3LYP/6-31G(d) and B3LYP/6-31+G(d) levels were carried out for the adsorption of NH₃ on three symmetric isomers of B₈₀ {C ₁, T _h, I _h}. To investigate the binding features of B₈₀ isomers with NH₃, different studies including the structural and electronic parameters, the ¹⁴N electric field gradient tensors and the atoms in molecules (AIM) properties were considered. The calculated parameters by these investigations can be used as powerful tools to find out some of the unknown aspects of electronic structures of the boron buckyball and its isomers. According to previous studies, boron buckyball as an amphoteric and a hard molecule has two distinct reactive sites defined as cap and frame which act as an acid and a base, respectively. Regarding the obtained results in this study, all the isomers had the same exposure when NH₃ molecule reacted with the external wall of B₈₀. For instance, the stability of N–B bond in the cap site was significantly more than the stability of N–B bond in the frame. Moreover, the adsorption of NH₃ on frame site showed a considerable reduction in HOMO–LUMO energy gap. According to AIM theory, an electrostatic nature was observed for N–B interaction. Concerning the selected isomers of buckyball, the capability of the NH₃–B₈₀ complexes to localize electron at the N–B bond critical points depend on the reaction sites significantly. In general, ¹⁴N nuclear quadruple coupling constants and asymmetry parameter reveal a remarkable effect of NH₃ adsorption on electronic structure of the B₈₀.     

Silphos [PCl3− n (SiO2) n ]: A Heterogeneous Phosphine Reagent for the Regioselective Synthesis of vic-Haloalcohols

Silphos as a silica-based phosphine [PCl_3?n (SiO₂) _n ] provides a practical method for the conversion of epoxides to vic-haloalcohols in the presence of molecular bromine, iodine, or N-halosuccinimides (NXS, X = Cl, Br, I) in CH₃CN or under solvent-free conditions at r.t. The simple filtration of heterogeneous Silphos oxide from the reaction mixture affords the pure vic-haloalcohols with excellent yields.     

Multiclass analysis on repaglinide,flubendazole, robenidine hydrochloride and danofloxacin drugs

The drugs under study; repaglinide (Repag), flubendazole (Flu), robenidine hydrochloride (Roben) and danofloxacin (Dano) are antidiabetic, anthelmintic, anticoccidial, and antibiotic drugs. In the present study, they are investigated using electron impact mass spectral (EI-MS) fragmentation at 70 eV, in comparison with thermal analyses measurements (TGA/DrTGA and DTA) and molecular orbital calculation (MO). Semi-empirical MO calculation, AM1 procedure, has been carried out on Repag, Flu, Roben and Dano both as neutral molecules (in TA) and the corresponding positively charged species (in MS). The calculated MO parameters include bond length, bond order, charge distribution on different atoms and heat of formation. The fragmentation pathways of Repag, Flu, Roben and Dano in EI-MS led to the formation of important primary and secondary fragment ions. The mechanism of formation of some important daughter ions can be illuminated from comparing with that obtained using mass spectrometer through the accurate mass measurement determination. The MO provides a base for fine distinction among sites of initial bond cleavage and subsequent fragmentation of drug molecules in both thermal analysis and MS techniques. The activation thermodynamic parameters, such as, (activation energy E¹), (enthalpy ΔH¹), (entropy ΔS¹) and (Gibbs free energy ΔG¹) are calculated from the DrTGA curves using Coats–Redfern and Horowitz–Mitzger methods.     

Chiral Separation of 4-Iminoflavan Derivatives on Several Polysaccharide-Based Chiral Stationary Phases by HPLC

The HPLC enantiomeric separation of seven 4-iminoflavans was successfully accomplished in the normal phase mode using six polysaccharide-based chiral stationary phases namely, Chiralcel^®OD-H, Chiralcel^®OD, Chiralcel^®OJ, Chiralpak^®AD, Chiralpak^®IA and Chiralpak^®IB under normal and polar organic phase modes. The resolution depended on nature and concentration of alcoholic modifier. The results demonstrate clearly that the chromatographic system based on the coated and immobilized type Chiralpak^®IB and Chiralcel^®OD-H CSPs provide a powerful analytical tool for enantiomeric separation of all the 4-iminoflavans used in this study.     

Alkaloids: Therapeutic Potential against Human Coronaviruses

Alkaloids are a class of natural products known to have wide pharmacological activity and have great potential for the development of new drugs to treat a wide array of pathologies. Some alkaloids have antiviral activity and/or have been used as prototypes in the development of synthetic antiviral drugs. In this study, eleven anti-coronavirus alkaloids were identified from the scientific literature and their potential therapeutic value against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is discussed. In this study, in silico studies showed an affinity of the alkaloids for binding to the receptor-binding domain of the SARS-CoV-2 spike protein, putatively preventing it from binding to the host cell. Lastly, several mechanisms for the known anti-coronavirus activity of alkaloids were discussed, showing that the alkaloids are interesting compounds with potential use as bioactive agents against SARS-CoV-2.     

GC-MS and GC-FID analyses of the volatile constituents of Brachychiton rupestris and Brachychiton discolor,their biological activities and their differentiation using multivariate data analysis

Abstract

The volatile constituents of the leaves and flowers of Brachychiton rupestris and Brachychiton discolor (Malvaceae) were characterized by GC-FID and GC-MS. A total of 92 compounds were identified. The major component of B. rupestris leaves was α-farnesene (34.57%) while in the flowers it was n-heptacosane (29.5%). (8Z, 11Z, 14Z)-heptadecatrienal (21.2%) in the leaves and palmitic acid (83.49%) in the flowers represent the abundant ingredients of B. discolor. Unsupervised pattern recognition techniques of multivariate data analysis exemplified by hierarchical cluster analysis (HCA) and principle component analysis (PCA) relying upon chromatographic results effectively discriminate the two related species. Also, both investigated species were assessed for their cytotoxic and antimicrobial efficacy. Results revealed that B. discolor flowers showed the highest cytotoxicity against human lung carcinoma (A-549) cell lines with IC₅₀ equals 7.98?μg/mL, whereas B. discolor leaves exhibited the highest antimicrobial potency against all tested microorganisms namely Streptococcus pneumonia, Bacillus subtilis, Escherichia coli as well as Aspergillus fumigatus and Geotrichum candidum (MICs between 0.98 and 15.63?µg/mL) except for Salmonella typhi.     

EGFR and COX-2 Dual Inhibitor: The Design,Synthesis, and Biological Evaluation of Novel Chalcones

For most researchers, discovering new anticancer drugs to avoid the adverse effects of current ones, to improve therapeutic benefits and to reduce resistance is essential. Because the COX-2 enzyme plays an important role in various types of cancer leading to malignancy enhancement, inhibition of apoptosis, and tumor-cell metastasis, an indispensable objective is to design new scaffolds or drugs that possess combined action or dual effect, such as kinase and COX-2 inhibition. The start compounds A1 to A6 were prepared through the diazo coupling of 3-aminoacetophenone with a corresponding phenol and then condensed with two new chalcone series, C7–18. The newly synthesized compounds were assessed against both COX-2 and epidermal growth factor receptor (EGFR) for their inhibitory effect. All novel compounds were screened for cytotoxicity against five cancer cell lines. Compounds C9 and G10 exhibited potent EGFR inhibition with IC₅₀ values of 0.8 and 1.1 µM, respectively. Additionally, they also displayed great COX-2 inhibition with IC₅₀ values of 1.27 and 1.88 µM, respectively. Furthermore, the target compounds were assessed for their cytotoxicity against pancreatic ductal cancer (Panc-1), lung cancer (H-460), human colon cancer (HT-29), human malignant melanoma (A375) and pancreatic cancer (PaCa-2) cell lines. Interestingly, compounds C10 and G12 exhibited the strongest cytotoxic effect against PaCa-2 with average IC₅₀ values of 0.9 and 0.8 µM, respectively. To understand the possible binding modes of the compounds under investigation with the receptor cites of EGFR and COX-2, a virtual docking study was conducted.     

A Novel Nonparametric Feature Selection Approach Based on Mutual Information Transfer Network

The filter feature selection algorithm is habitually used as an effective way to reduce the computational cost of data analysis by selecting and implementing only a subset of original features into the study. Mutual information (MI) is a popular measurement adopted to quantify the dependence among features. MI-based greedy forward methods (MIGFMs) have been widely applied to escape from computational complexity and exhaustion of high-dimensional data. However, most MIGFMs are parametric methods that necessitate proper preset parameters and stopping criteria. Improper parameters may lead to ignorance of better results. This paper proposes a novel nonparametric feature selection method based on mutual information and mixed-integer linear programming (MILP). By forming a mutual information network, we transform the feature selection problem into a maximum flow problem, which can be solved with the Gurobi solver in a reasonable time. The proposed method attempts to prevent negligence on obtaining a superior feature subset while keeping the computational cost in an affordable range. Analytical comparison of the proposed method with six feature selection methods reveals significantly better results compared to MIGFMs, considering classification accuracy.