Design, synthesis, molecular modelling and biological evaluation of novel 6-amino-5-cyano-2-thiopyrimidine derivatives as potent anticancer agents against leukemia and apoptotic inducers

Herein, a novel series of 6-amino-5-cyano-2-thiopyrimidines and condensed pyrimidines analogues were prepared. All the synthesized compounds (1a-c, 2a-c, 3a-c, 4a-r and 5a-c) were evaluated for in vitro anticancer activity by the National Cancer Institute (NCI; MD, USA) against 60 cell lines. Compound 1c showed promising anticancer activity and was selected for the five-dose testing. Results demonstrated that compound 1c possessed broad spectrum anti-cancer activity against the nine cancerous subpanels tested with selectivity ratio ranging from 0.7 to 39 at the GI50 level with high selectivity towards leukaemia. Mechanistic studies showed that Compound 1c showed comparable activity to Duvelisib against PI3Kδ (IC50 = 0.0034 and 0.0025 μM, respectively) and arrested cell cycle at the S phase and displayed significant increase in the early and late apoptosis in HL60 and leukaemia SR cells. The necrosis percentage showed a significant increase from 1.13% to 3.41% in compound 1c treated HL60 cells as well as from 1.51% to 4.72% in compound 1c treated leukaemia SR cells. Also, compound 1c triggered apoptosis by activating caspase 3, Bax, P53 and suppressing Bcl2. Moreover, 1c revealed a good safety profile against human normal lung fibroblast cell line (WI-38 cells). Molecular analysis of Duvelisib and compound 1c in PI3K was performed. Finally, these results suggest that 2-thiopyrimidine derivative 1c might serve as a model for designing novel anticancer drugs in the future.

Synthesis of Biologically Relevant 1,2,3- and 1,3,4-Triazoles: From Classical Pathway to Green Chemistry

Green Chemistry has become in the last two decades an increasing part of research interest. Nonconventional «green» sources for chemical reactions include micro-wave, mechanical mixing, visible light and ultrasound. 1,2,3-triazoles have important applications in pharmaceutical chemistry while their 1,2,4 counterparts are developed to a lesser extent. In the review presented here we will focus on synthesis of 1,2,3 and 1,2,4-triazole systems by means of classical and « green chemistry » conditions involving ultrasound chemistry and mechanochemistry. The focus will be on compounds/scaffolds that possess biological/pharmacophoric properties. Finally, we will also present the formal cycloreversion of 1,2,3-triazole compounds under mechanical forces and its potential use in biological systems.

Iodine Catalyzed Oxidative Coupling of Diaminoazines and Amines for the Synthesis of 3,5-Disubstituted-1,2,4-Triazoles

A simple, convenient, transition metal-free one pot synthesis of 3,5-disubstituted-1,2,4-triazoles has been established. The innovation in this reaction is the use of easily available 1,1-diaminoazines as substrates. This method provides the products with wider substrate scope, at an expedited rate, and with relatively better yields in comparison to the reported methods. The reaction mechanism involves an initial intermolecular nucleophilic addition (facilitated by I₂) followed by intramolecular nucleophilic cyclization.

Photostable NIR emitting ruthenium(II) conjugates; uptake and biological activity in live cells

A photostable Ru(2,2-biquinoline)₂(3-(2-pyridyl)-5-(4-carboxyphenyl)-1,2,4-triazolate) (Ru(biq)₂(trzbenzCOOH)) complex that exhibits near-infrared (NIR) emission centred at 786 nm is reported. The parent complex was conjugated via amide coupling to a cell-penetrating peptide sequence octa-arginine (R8), and two signal peptide sequences; the nuclear localizing sequence (NLS) VQRKRQKLMP and the mitochondria penetrating peptide (MPP) FrFKFrFK(Ac) (r = D isomer of arginine, Ac = terminal lysine amine acetyl blocked). Notably, none of the peptide conjugates were cell-permeable as chloride salts but efficient and rapid membrane permeation was observed post ion exchange with perchlorate counterion. Also, surprisingly, all three peptide conjugates exhibited potent dark cytotoxicity in both CHO and HeLa cell lines. The peptide conjugates induce cell death through a caspase dependent apoptotic pathway. At the minimum concentration of dye (approx. 15 μM) required for cell imaging, only 20% of the cells were viable after a 24 h incubation period. To overcome cytotoxicity, the parent complex was PEGylated; this dramatically decreased cytotoxicity, where 50% of cells were viable even at 150 μM concentration after 24 h. Confocal luminescence microscopy indicated that all four bioconjugates, peptides in perchlorate form and polyethylene glycol (PEG) in chloride form, were rapidly internalized within the cell. However, interestingly the precise localisation by the signal peptides observed in related complexes was not observed here and the peptide conjugates were unsuitable as luminescent probes for cell microscopy due to their high cell toxicity. The poor targeting of signal peptides in this instance is attributed to the high lipophilicity of the metal centre.

New syntheses towards C-glycosyl type glycomimetics

Glycomimetics are compounds that resemble carbohydrate molecules in their chemical structure and/or biological effect. A large variety of compounds can be designed and synthesized to get glycomimetics, however, C-glycosyl derivatives represent one of the most frequently studied subgroup. In the present survey syntheses of a range of five- and six membered C-glycopyranosyl heterocycles, anhydro-aldimine type compounds, exo-glycals, C-glycosyl styrenes, carbon-sulfur bonded oligosaccharide mimics are described. Some of the C-glycopyranosyl azoles, namely 1,2,4-triazoles and imidazoles belong to the most efficient glucose analog inhibitors of glycogen phosphorylase known to date. Biological studies revealed the therapeutical potential of such inhibitors. Other synthetic derivatives offer versatile possibilities to get further glycomimetics.

Azines: synthesis, structure, electronic structure and their applications

Azines (2,3-diaza-1,3-butadienes): structure, electronic structure, tautomerism, and their applications in organic synthesis, medicinal chemistry and materials chemistry.

Nanomolar Inhibitors of Glycogen Phosphorylase Based on β-d-Glucosaminyl Heterocycles: A Combined Synthetic, Enzyme Kinetic, and Protein Crystallography Study

Aryl substituted 1-(β-d-glucosaminyl)-1,2,3-triazoles as well as C-β-d-glucosaminyl 1,2,4-triazoles and imidazoles were synthesized and tested as inhibitors against muscle and liver isoforms of glycogen phosphorylase (GP). While the N-β-d-glucosaminyl 1,2,3-triazoles showed weak or no inhibition, the C-β-d-glucosaminyl derivatives had potent activity, and the best inhibitor was the 2-(β-d-glucosaminyl)-4(5)-(2-naphthyl)-imidazole with a K_i value of 143 nM against human liver GPa. An X-ray crystallography study of the rabbit muscle GPb inhibitor complexes revealed structural features of the strong binding and offered an explanation for the differences in inhibitory potency between glucosyl and glucosaminyl derivatives and also for the differences between imidazole and 1,2,4-triazole analogues.

C-Glycopyranosyl Arenes and Hetarenes: Synthetic Methods and Bioactivity Focused on Antidiabetic Potential

This Review summarizes close to 500 primary publications and surveys published since 2000 about the syntheses and diverse bioactivities of C-glycopyranosyl (het)arenes. A classification of the preparative routes to these synthetic targets according to methodologies and compound categories is provided. Several of these compounds, regardless of their natural or synthetic origin, display antidiabetic properties due to enzyme inhibition (glycogen phosphorylase, protein tyrosine phosphatase 1B) or by inhibiting renal sodium-dependent glucose cotransporter 2 (SGLT2). The latter class of synthetic inhibitors, very recently approved as antihyperglycemic drugs, opens new perspectives in the pharmacological treatment of type 2 diabetes. Various compounds with the C-glycopyranosyl (het)arene motif were subjected to biological studies displaying among others antioxidant, antiviral, antibiotic, antiadhesive, cytotoxic, and glycoenzyme inhibitory effects.

A Target-Based Whole Cell Screen Approach To Identify Potential Inhibitors of Mycobacterium tuberculosis Signal Peptidase

The general secretion (Sec) pathway is a conserved essential pathway in bacteria and is the primary route of protein export across the cytoplasmic membrane. During protein export, the signal peptidase LepB catalyzes the cleavage of the signal peptide and subsequent release of mature proteins into the extracellular space. We developed a target-based whole cell assay to screen for potential inhibitors of LepB, the sole signal peptidase in Mycobacterium tuberculosis, using a strain engineered to underexpress LepB (LepB-UE). We screened 72,000 compounds against both the Lep-UE and wild-type (wt) strains. We identified the phenylhydrazone (PHY) series as having higher activity against the LepB-UE strain. We conducted a limited structure-activity relationship determination around a representative PHY compound with differential activity (MICs of 3.0 μM against the LepB-UE strain and 18 μM against the wt); several analogues were less potent against the LepB overexpressing strain. A number of chemical modifications around the hydrazone moiety resulted in improved potency. Inhibition of LepB activity was observed for a number of compounds in a biochemical assay using cell membrane fraction derived from M. tuberculosis. Compounds did not increase cell permeability, dissipate membrane potential, or inhibit an unrelated mycobacterial enzyme, suggesting a specific mode of action related to the LepB secretory mechanism.

Glycogen phosphorylase inhibitors: a patent review (2013 - 2015)

INTRODUCTION

Control of glycemia is crucial in the treatment of type 2 diabetes complications. Glycogen phosphorylase (GP) releases glucose from the liver into the blood stream. Design of potent GP inhibitors is a therapeutic strategy in the context of type 2 diabetes.

AREAS COVERED

Glucose-based inhibitors have found potential applications since they now reach low nanomolar Ki values. Another set of patents disclose cholic acid/7-aza-indole conjugates for targeted drug delivery to the liver. A series of benzazepinones have also been reported as potent GP inhibitors. In vitro data are reported for GP inhibition but the in vivo biological data at the cellular or animal levels are often missing, even though the literature reported for these molecules is also discussed.

EXPERT OPINION

A structural analogy between glucose-based GP inhibitors and C-glucosides targeting sodium glucose co-transporter 2 (SGLT2) is intriguing. Cholic acid/7-aza-indole conjugates are promising in vivo drug delivery systems to the liver. Benzazepinones were very recently described and no associated literature is available, making it very difficult to comment at present. While industry has slowed down on GP inhibitors design, academic groups are pursuing investigations and have provided potential drug candidates which will resuscitate the interest for GP, including its potential for targeting cancer.