Synthesis and evaluation of novel ureido/thioureido derivatives of amino acid conjugated 2,3-dichlorophenyl piperazine as highly potent antiglycating agents

Conjugation as a Tool in Therapeutics: Role of Amino Acids/Peptides-Bioactive (Including Heterocycles) Hybrid Molecules in Treating Infectious Diseases

Peptide-based drugs are gaining significant momentum in the modern drug discovery, which is witnessed by the approval of new drugs by the FDA in recent years. On the other hand, small molecules-based drugs are an integral part of drug development since the past several decades. Peptide-containing drugs are placed between small molecules and the biologics. Both the peptides as well as the small molecules (mainly heterocycles) pose several drawbacks as therapeutics despite their success in curing many diseases. This gap may be bridged by utilising the so called 'conjugation chemistry', in which both the partners are linked to one another through a stable chemical bond, and the resulting conjugates are found to possess attracting benefits, thus eliminating the stigma associated with the individual partners. Over the past decades, the field of molecular hybridisation has emerged to afford us new and efficient molecular architectures that have shown high promise in medicinal chemistry. Taking advantage of this and also considering our experience in this field, we present herein a review concerning the molecules obtained by the conjugation of peptides (amino acids) to small molecules (heterocycles as well as bioactive compounds). More than 125 examples of the conjugates citing nearly 100 references published during the period 2000 to 2022 having therapeutic applications in curing infectious diseases have been covered.

Multitarget-directed therapeutics: (Urea/thiourea)2 derivatives of diverse heterocyclic-Lys conjugates

The synthesis of a new small library of molecules containing bis-urea/thiourea pendants in lysine conjugated to three different heterocycles is described. The heterocycles used in this study have benzisoxazole/piperazine/piperidine units. After a detailed antimicrobial, antioxidant, and anti-inflammatory evaluation, it was found that the most active compounds are 10, 11, 14, 15, 18, 19 and 10, 11, 19 and 8, 9, 12, 13, 16, 17, respectively. Further, it was observed that the presence of all three entities, that is, urea/thiourea, the substituent (OMe/F), as well as the heterocycle, is highly essential for exerting potent activity. Among the heterocycles, the presence of isoxazole seems to be highly beneficial for exerting good potency. In continuation, docking studies have revealed extraordinary binding efficiency for some of the active compounds. Given their potent biological results and docking score, some of the title compounds could be potential drug candidates for microbial-related diseases and provide a basis for future research into the development of molecules possessing multitask ability.

Design, synthesis, anti-tobacco mosaic viral and molecule docking simulations of urea/thiourea derivatives of 2-(piperazine-1-yl)-pyrimidine and 1-(4-Fluoro/4-Chloro phenyl)-piperazine and 1-(4-Chloro phenyl)-piperazine - A study

The objectives of the present work are to design, syhthesize and introduce novel urea/thiourea derivatives of 2-(piperazine-1-yl)-pyrimidine and 1-(4-Fluoro/4-Chloro phenyl)-piperazine molecules as tobacco mosaic virus (TMV) inhibitors. A series of urea/thiourea derivatives containing pyrimidine and piperazine moieties were synthesized, characterized using Fourier-transform infrared (FTIR) mass spectra, nuclear magnetic resonance (NMR) spectroscopy, elemental analysis and evaluated their sustainability using biological experiments. The anti-viral bioassay of the title compounds showed an antiviral activity against TMV. The compounds synthesized, 9j, 6g and 3d, showed highly-potential curative, protective, and inhibitory activities against TMV at 500 mg/mL formulation. All these compounds were allowed to quantum-polarized-ligand (quantum mechanical and molecular mechanical (QM/MM)) docking experiments. The compounds 9j, 6g and 3d structurally exhibited identical higher affinity towards TMV-Helicase and TMV-Coat proteins. The docking interactions proposed had two stage inhibition of TMV virus by binding to coat protein and helicase for inhibition of RNA replication. The long-range molecular dynamics (150 ns) simulations has revealed more consistency by 9j, 6g and 3d. The present study outcomes good binding propensity for active-tunnel of TMV-Hel enzyme, by these thiourea, urea derivatives, 9j, 6g and 3d, to suggest that the designed and synthesized were ideal for proposing as selective novel inhibitors to target for TMV.

Synthesis of amino acid derivatives of 5-alkoxy-3,4-dihalo-2(5H)-furanones and their preliminary bioactivity investigation as linkers

A series of amino acid derivatives are successfully synthesized via a metal-free C-N coupling reaction of 5-alkoxy-3,4-dihalo-2(5H)-furanones and amino acids. Their structures are well characterized with ¹H NMR, ¹³C NMR, ESI-MS and elemental analysis. As potential linkers of the 2(5H)-furanone unit with other drug moieties containing a hydroxyl or amino group, the effect of amino acids is investigated by comparison with other 2(5H)-furanone compounds by constructing C-O/C-S bonds. The preliminary results of the biological activity assay by the MTT method on a series of cancer cell lines in vitro reveal that the introduction of amino acids basically has no toxic effect. This can lead to these 2(5H)-furanone derivatives being further well-linked with other bioactive moieties with amino or hydroxy groups as expected. Thus, the biological activity assay gives a direction for the design of bioactive 2(5H)-furanones based on these amino acid linkers.

Revisiting amino acids and peptides as anti-glycation agents

The importance of controlling or preventing protein glycation cannot be overstated and is of prime importance in the treatment of diabetes and associated complications including Alzheimer's disease, cataracts, atherosclerosis, kidney aliments among others. In this respect, simple molecules such as amino acids and peptides hold much promise both in terms of ease and scale-up of synthesis as well as in relation to negligible/low associated toxicity. In view of this, a comprehensive account of literature reports is presented, that documents the anti-glycation activity of natural and non-natural amino acids and peptides. This review also discusses the chemical reactions involved in glycation and the formation of advanced glycation end-products (AGEs) and possible/probable intervention sites and mechanism of action of the reported amino acids/peptides. This aspect of amino acids/peptides adds to their growing importance in medicinal and therapeutic applications.

Synthesis, crystal structure, molecular docking studies and bio-evaluation of some N4-benzyl-substituted isatin- 3-thiosemicarbazones as urease and glycation inhibitors

Fifteen N4-benzyl-substituted isatin-3-thiosemicarbazones 5a–o were synthesized and evaluated for their urease and glycation inhibitory potential. Lemna aequinocitalis growth and Artemia salina assays were also done to determine their phytotoxic and toxic effects. All compounds are potent inhibitors of the urease enzyme, displaying inhibition [half maximal inhibitory concentration (IC50)=1.08±0.12–11.23±0.19 μm] superior to that of the reference inhibitor thiourea (IC50=22.3±1.12 μm). Compounds 5c, 5d, 5h, 5j,k are potent antiglycating agents, showing glycation inhibitory activity better than that of the reference inhibitor rutin (IC50 values 209.87±0.37–231.70±6.71 vs. 294.5±1.5 μm). In the phytotoxicity assay, 11 thiosemicarbazones 5a–d, 5g, 5h, 5j–l, 5n,o are active, demonstrating 5–100% growth inhibition of L. aequinocitalis at the highest tested concentrations (1000 or 500 μg/mL). In the brine shrimp (A. salina) lethality bioassay, three derivatives 5b, 5j and 5o are active with median lethal dose (LD50) values of 3.63×10−5, 2.90×10−5 and 2.31×10−4 m, respectively.

Amino acids/peptides conjugated heterocycles: A tool for the recent development of novel therapeutic agents

Amino acids/peptide conjugated heterocycles represent an important class of therapeutical agents. Biologically active heterocycles are conjugated with amino acids or peptides to increase the drug resistance. Furthermore, the amino acid/peptide based drugs have low toxicity, ample bioavailability and permeability, modest potency and good metabolic and pharmacokinetic properties. Synthetic amino acid/peptides based heterocyclic conjugates constitute a promising choice for the development of new, less toxic and safer conventional pharmaceutical drugs in the near future. In this review, we discuss and highlight the recent findings of the structural features that encourage biological applications of amino acid/peptides based conjugates.