Solid-phase synthesis and biological evaluation of a parallel library of 2,3-dihydro-1,5-benzothiazepines

Synthesis, characterization, in vitro cholinesterase and hRBCs hemolysis assay and computational evaluation of novel 2,3,4,5-tetrahydrobenzothiazepine appended α-aminophosphonates

A series of novel 2,3,4,5-tetrahydrobenzothiazepine appended α-aminophosphonate derivatives were synthesized by subjecting 2,3-dihydrobenzothiazepine to Pudovik reaction using diethyl phosphite. Tested derivatives exhibited better AChE inhibition (0.86-12.85 µM) when compared to BuChE (3.13-19.36 µM). Derivative 5f (IC₅₀ = 0.86 ± 0.08 µM), 5g (IC₅₀ = 1.05 ± 0.06 µM) and 5d (IC₅₀ = 1.64 ± 0.06 µM) exhibited higher AChE inhibitory activity as compared to standard drug galantamine (IC₅₀ = 2.15 ± 0.05 µM). Similarly, derivative 5e (IC₅₀ = 3.13 ± 0.11 µM) and 5f (IC₅₀ = 3.64 ± 0.06 µM) demonstrated comparable BuChE inhibitory activity to reference drug galantamine (IC₅₀ = 3.86 ± 0.03 µM). Further, enzyme kinetic studies were carried out for the most active molecule i.e. derivative 5f (for AChE) and derivative 5e (for BuChE) and the results imply that derivatives 5f and 5e show mixed-type inhibition with K_i values of 1.779 µM and 3.851 µM respectively. Enzyme reversibility inhibition studies demonstrated that all the tested derivatives possess reversible inhibitor characteristics. In addition, % hemolysis studies were carried out using human red blood cells (hRBCs) and the results demonstrated that the synthesized derivatives were biocompatible in nature as they impart very less cytotoxicity to hRBCs (CC₅₀ > 1000 μg/mL). Also, cell viability studies for tested derivatives revealed no cytotoxicity in N2a cells. Moreover, molecular docking studies revealed that derivative 5e and 5f bind to the PAS and CAS of the AChE. ADME predictions suggested that synthesized derivatives have high possibility of being drug-like.

New chalcone-3-O-glycoside derivatives: Synthesis and characterization

Seven novel carbohydrate conjugates of new chalcone-3- O-glycosides were synthesized and characterized. Starting from the substituted 3′-hydroxyarylmethylacetophenone derivatives (chalcones) with α-acetobromoglucose in anhydrous acetone were synthesized 2,3,4,6-tetra- O-acetyl-3′- O-β-d-glucopyranosyloxychalcones. Deblocking the latter with CH3ONa in dry methanol results in substituted chalcone-3- O-glycosides (3′- O-β-d-glucopyranosyloxychalcones). The structures of the newly synthesized chalcone-3- O-glycosides were characterized based on1H nuclear magnetic resonance,13C nuclear magnetic resonance, mass spectroscopy, and Fourier-transform infrared spectroscopy.

Synthesis and biological evaluation of newer 1,3,4-oxadiazoles incorporated with benzothiazepine and benzodiazepine moieties

A series of thiazepines and diazepines having 1,3,4-oxadiazole moiety were synthesized, and they were analyzed for their in vitro antimicrobial activity against several bacteria (Staphylococcus aureus, Staphylococcus pyogenes, Escherichia coli, and Pseudomonas aeruginosa) and fungi (Candida albicans, Aspergillus niger, and Aspergillus Clavatus) and protozoa (Entamoeba histolytica, Giardia lamblia, Trypanosoma cruzi and Leishmania mexicana). Few of the selected compounds were tested for their antitubercular activity. However, it was noticed that the potency of final analogs against each strain placed reliance on the type of substituent present on aryl ring of oxadiazole as well as presence of thiophene, pyridine, and furan at benzothiazepines and benzodiazepines. The biological screening identified that some of the compounds were found to possess good antimicrobial and antitubercular (62.5-100 μg/mL of MIC) activity.

Molecular modeling and synthesis of new 1,5-diphenylpyrazoles as breast cancer cell growth inhibitors

New pyrazoles have been synthesized and evaluated as breast cancer cell growth inhibitors. Condensation of the substituted pyrazole-4-carbaldehyde1with acetophenone and chloroacetophenone afforded α, β-unsaturated ketones2and3, respectively. Compounds2and3were subjected to different reactions using hydrazine hydrate, substituted hydrazine hydrate, hydroxylamine,o-phenylenediamine, malononitrile under different conditions affording 4-substituted pyrazole derivatives4–28. Structure elucidation of these compounds was conducted using IR,1H NMR,13C NMR, mass spectral data and elemental analysis. Antitumor activity of target compounds was tested against MCF-7 cell line (human breast cancer). Compounds4,10and20show significant antitumor activity against breast cancer. Docking was performed with protein 1UYK to study the binding mode of the designed compounds.

In silico modeling of the specific inhibitory potential of thiophene-2,3-dihydro-1,5-benzothiazepine against BChE in the formation of beta-amyloid plaques associated with Alzheimer's disease

Background

Alzheimer's disease, known to be associated with the gradual loss of memory, is characterized by low concentration of acetylcholine in the hippocampus and cortex part of the brain. Inhibition of acetylcholinesterase has successfully been used as a drug target to treat Alzheimer's disease but drug resistance shown by butyrylcholinesterase remains a matter of concern in treating Alzheimer's disease. Apart from the many other reasons for Alzheimer's disease, its association with the genesis of fibrils by β-amyloid plaques is closely related to the increased activity of butyrylcholinesterase. Although few data are available on the inhibition of butyrylcholinesterase, studies have shown that that butyrylcholinesterase is a genetically validated drug target and its selective inhibition reduces the formation of β-amyloid plaques.

Rationale

We previously reported the inhibition of cholinesterases by 2,3-dihydro-1, 5-benzothiazepines, and considered this class of compounds as promising inhibitors for the cure of Alzheimer's disease. One compound from the same series, when substituted with a hydroxy group at C-3 in ring A and 2-thienyl moiety as ring B, showed greater activity against butyrylcholinesterase than to acetylcholinesterase. To provide insight into the binding mode of this compound (Compound A), molecular docking in combination with molecular dynamics simulation of 5000 ps in an explicit solvent system was carried out for both cholinesterases.

Conclusion

Molecular docking studies revealed that the potential of Compound A to inhibit cholinesterases was attributable to the cumulative effects of strong hydrogen bonds, cationic-π, π-π interactions and hydrophobic interactions. A comparison of the docking results of Compound A against both cholinesterases showed that amino acid residues in different sub-sites were engaged to stabilize the docked complex. The relatively high affinity of Compound A for butyrylcholinesterase was due to the additional hydrophobic interaction between the 2-thiophene moiety of Compound A and Ile69. The involvement of one catalytic triad residue (His438) of butyrylcholinesterase with the 3'-hydroxy group on ring A increases the selectivity of Compound A. C-C bond rotation around ring A also stabilizes and enhances the interaction of Compound A with butyrylcholinesterase. Furthermore, the classical network of hydrogen bonding interactions as formed by the catalytic triad of butyrylcholinesterase is disturbed by Compound A. This study may open a new avenue for structure-based drug design for Alzheimer's disease by considering the 3D-pharmacophoric features of the complex responsible for discriminating these two closely-related cholinesterases.