Synthesis, Characterisation and Acetylcholinesterase-Inhibition Activities of 5-benzyl-1,3,4-thiadiazol-2-amine Derivatives

Synthesis, characterization, biochemical, and molecular modeling studies of carvacrol-based new thiosemicarbazide and 1,3,4-thiadiazole derivatives

A series of carvacrol-based thiosemicarbazide (3a-e) and 1,3,4-thiadiazole-2-amine (4a-e) were designed and synthesized for the first time. The structures were characterized by nuclear magnetic resonance and high resolution mass spectroscopy techniques. All compounds were examined for some metabolic enzyme activities. Results indicated that all the synthetic molecules exhibited powerful inhibitory actions against human carbonic anhydrase I and II (hCAI and II), acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) enzymes compared to the standard molecules. Ki values of five novel thiosemicarbazides and five new 1,3,4-thiadiazole-2-amine derivatives (3a-e and 4a-e) for hCA I, hCA II, AChE, and BChE enzymes were obtained in the ranges 0.73-21.60, 0.42-15.08 µM, 3.48-81.48, 92.61-211.40 nM, respectively. After the experimental undertaking, an extensive molecular docking analysis was conducted to scrutinize the intricate details of interactions between the ligand and the enzyme in question. The principal focus of this investigation was to appraise the potency and efficacy of the most active compound. In this context, the calculated docking scores were noted to be remarkably low, with values of -8.65, -7.97, -8.92, and -8.32 kcal/mol being recorded for hCA I, hCA II, AChE, and BChE, respectively. These observations suggest a high affinity and specificity of the studied compounds toward the enzymes, as mentioned earlier, which may pave the way for novel therapeutic interventions aimed at modulating the activity of these enzymes.

Thiadiazole – A promising structure in design and development of anti-Alzheimer agents

The design and development of effective multitargeted agents in treating Alzheimer disease (AD) has always been a hot topic in the field of drug discovery. Since AD is a multifactorial disorder, various key hidden players such as deficit of acetylcholine (ACh), tau-protein aggregation, and oxidative stress have been associated with the incidence and progress of AD. In pursuit of improving efficacy and expanding the range of pharmacological activities of current AD drugs, the molecular hybridization method is also used intensively. Five-membered heterocyclic systems such as thiadiazole scaffolds have previously been shown to have therapeutic activity. Thiadiazole analogs as an anti-oxidant compound have been known to include a wide range of biological activity from anti-cancer to anti-Alzheimer properties. The suitable pharmacokinetic and physicochemical properties of the thiadiazole scaffold have introduced it as a therapeutic target in medicinal chemistry. The current review portrays the critical role of the thiadiazole scaffold in the design of various compounds with potential effects in the treatment of Alzheimer's disease. Furthermore, the rationale used behind hybrid-based design strategies and the outcomes achieved through the hybridization of Thiadiazole analogs with various core structures have been discussed. In addition, the data in the present review may help researchers in the design of new multidrug combinations that may provide new options for the treatment of AD.

Synthesis, characterizations of aryl-substituted dithiodibenzothioate derivatives, and investigating their anti-Alzheimer's properties

The main objective of the present study was to synthesize potential inhibitor/activators of AChE and hCA I-II enzymes, which are thought to be directly related to Alzheimer's disease. Dithiodibenzothioate compounds were synthesized by thioesterification. Six different thiolate compounds produced were characterized by ¹H-, ¹³C-NMR, FT-IR, LC-MS/MS methods. HOMO-LUMO calculations and electronic properties of all synthesized compounds were comprehensively illuminated with a semi-empirical molecular orbital (SEMO) package for organic and inorganic systems using Austin Model 1 (AM1)-Hamiltonian as implemented in the VAMP module of Materials Studio. In addition, the inhibition effects of these compounds for AChE and hCA I-II in vitro conditions were investigated. It was revealed that TE-1, TE-2, TE-3, TE-4, TE-5, and TE-6 compounds inhibited the AChE under in vitro conditions. TE-1 compound activated the enzyme hCA I while TE-2, TE-3 TE-4 compounds inhibited it. TE-5 and TE-6, on the other hand, did not exhibit a regular inhibition profile. Similarly, TE-1 activated the hCA II enzyme whereas TE-2, TE-3, TE-4, and TE-5 compounds inhibited it. TE-6 compound did not have a consistent inhibition profile for hCA II. Docking studies were performed with the compounds against AChE and hCA I-II receptors using induced-fit docking method. Molecular Dynamics (MD) simulations for best effective three protein-ligand couple were conducted to explore the binding affinity of the considered compounds in semi-real in-silico conditions. Along with the MD results, TE-1-based protein complexes were found more stable than TE-5. Based on these studies, TE-1 compound could be considered as a potential drug candidate for AD.Communicated by Ramaswamy H. Sarma.

Diversity-Oriented Synthesis of 1,2,4-Triazols, 1,3,4-Thiadiazols, and 1,3,4-Selenadiazoles from N-Tosylhydrazones

The diversity-oriented synthesis of 1,2,4-triazols, 1,3,4-thiadiazols, and 1,3,4-selenadiazoles from N-tosylhydrazones was developed, and the reactions were general for a wide range of substrates, in which NH₂CN, KOCN, KSCN, and KSeCN were used as odorless sources. Two different pathways were proposed, and N-tosylhydrazonoyl chlorides were formed in situ in the presence of NCS.

Synthesis and Evaluation of 5-Benzyl-1,3,4-Thiadiazole Derivatives as Acetylcholinesterase Inhibitors

Three novel 5-benzyl-1,3,4-thiadiazole derivatives were synthesised starting from phenylacetic acid derivatives. These compounds were characterised by NMR, HRMS and single-crystal X-ray diffraction analysis. 2-Pyrrolidyl-5-[2-(4-bromophenyl)methyl]-1,3,4-thiadiazole showed moderate acetylcholinesterase-inhibition activity with a 50% inhibitory concentration value of 33.16 μM. 2-Pyrrolidyl-5-[2-(4-bromophenyl)methyl]-1,3,4-thiadiazole and acetylcholinesterase docking was demonstrated using the Molecular Operating Environment program.