Facile fabrication of promising protein tyrosine phosphatase (PTP) inhibitor entities based on ‘clicked’ serine/threonine–monosaccharide hybrids

1H-1,2,3-Triazole-4H-chromene-D-glucose hybrid compounds: Synthesis and inhibitory activity against Mycobacterium tuberculosis protein tyrosine phosphatase B

A series of 1H-1,2,3-triazole-4H-chromene-D-glucose hybrid compounds 7a-w were synthesized using click chemistry of 2-amino-7-propargyloxy-4H-chromene-3-carbonitriles 5a-w. CuNPs@montmorillonite was used as a catalyst in the presence of DIPEA as an additive for this chemistry. All synthesized 1H-1,2,3-triazoles were examined for in vitro inhibition against Mycobacterium tuberculosis protein tyrosine phosphatase B (MtbPtpB). Nine 1H-1,2,3-triazoles, including 7c-e, 7h, 7i, and 7r-t, displayed remarkable inhibitory activity against MtbPtpB with IC₅₀  < 10 μM; compound 7t exhibited the most potent inhibition in vitro with an IC₅₀ value of 0.61 μM. Kinetic studies of the three most active compounds, 7c,h,t, showed their competitive inhibition toward the MtbPtpB enzyme. Induced-fit docking and MM-GBSA studies on the enzyme (PDB: 2OZ5) revealed that the most active compound 7t was more effective against MtbPtpB. Residues Arg64, Arg136, Ash165, Arg166, and Arg63 in the binding pocket were identified as potential ligand-binding hot-spot residues for ligand 7t. The binding free energy calculation by the MM-GBSA approach for ligand 7t indicated that Coulomb, lipophilic, and van der Waals energy terms are major contributors to the inhibitor binding. Furthermore, the stability of the ligand-protein complex and the structural insights into the mode of binding were confirmed by 300-ns molecular dynamics simulation of 7t/2OZ5.

One-Pot Synthesis of 2-C-Branched Glycosyl Triazoles by Integrating 1,2-Cyclopropanated Sugar Ring-Opening Azidation and CuAAC Reaction

A series of 2-C-branched glycosyl triazoles including triazole-tethered oligosaccharides and glycopeptides were synthesized in one pot from 1,2-cyclopropanated sugars or 2'-acetonyl-2-O-Ts-C-furanosides, NaN₃, and alkynes using PEG-400 as a single solvent. Nucleophilic ring-opening azidation of 1,2-cyclopropanated sugars (or 2'-acetonyl group 1,2-migration-azidation of C-furanosides) obtained glycosyl azides, which upon reaction with alkynes under CuAAC conditions achieved glycosyl triazoles in good yields and high stereoselectivity without the need to change the solvent and isolate any intermediates.

Cu(I)-Catalyzed Click Chemistry in Glycoscience and Their Diverse Applications

Copper(I)-catalyzed 1,3-dipolar cycloaddition between organic azides and terminal alkynes, commonly known as CuAAC or click chemistry, has been identified as one of the most successful, versatile, reliable, and modular strategies for the rapid and regioselective construction of 1,4-disubstituted 1,2,3-triazoles as diversely functionalized molecules. Carbohydrates, an integral part of living cells, have several fascinating features, including their structural diversity, biocompatibility, bioavailability, hydrophilicity, and superior ADME properties with minimal toxicity, which support increased demand to explore them as versatile scaffolds for easy access to diverse glycohybrids and well-defined glycoconjugates for complete chemical, biochemical, and pharmacological investigations. This review highlights the successful development of CuAAC or click chemistry in emerging areas of glycoscience, including the synthesis of triazole appended carbohydrate-containing molecular architectures (mainly glycohybrids, glycoconjugates, glycopolymers, glycopeptides, glycoproteins, glycolipids, glycoclusters, and glycodendrimers through regioselective triazole forming modular and bio-orthogonal coupling protocols). It discusses the widespread applications of these glycoproducts as enzyme inhibitors in drug discovery and development, sensing, gelation, chelation, glycosylation, and catalysis. This review also covers the impact of click chemistry and provides future perspectives on its role in various emerging disciplines of science and technology.

The design strategy of selective PTP1B inhibitors over TCPTP

Protein tyrosine phosphatase 1B (PTP1B) has already been well studied as a highly validated therapeutic target for diabetes and obesity. However, the lack of selectivity limited further studies and clinical applications of PTP1B inhibitors, especially over T-cell protein tyrosine phosphatase (TCPTP). In this review, we enumerate the published specific inhibitors of PTP1B, discuss the structure-activity relationships by analysis of their X-ray structures or docking results, and summarize the characteristic of selectivity related residues and groups. Furthermore, the design strategy of selective PTP1B inhibitors over TCPTP is also proposed. We hope our work could provide an effective way to gain specific PTP1B inhibitors.

Cu-Catalyzed Click Reaction in Carbohydrate Chemistry

Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC), popularly known as the "click reaction", serves as the most potent and highly dependable tool for facile construction of simple to complex architectures at the molecular level. Click-knitted threads of two exclusively different molecular entities have created some really interesting structures for more than 15 years with a broad spectrum of applicability, including in the fascinating fields of synthetic chemistry, medicinal science, biochemistry, pharmacology, material science, and catalysis. The unique properties of the carbohydrate moiety and the advantages of highly chemo- and regioselective click chemistry, such as mild reaction conditions, efficient performance with a wide range of solvents, and compatibility with different functionalities, together produce miraculous neoglycoconjugates and neoglycopolymers with various synthetic, biological, and pharmaceutical applications. In this review we highlight the successful advancement of Cu(I)-catalyzed click chemistry in glycoscience and its applications as well as future scope in different streams of applied sciences.

Novel PTP1B inhibitors identified by DNA display of fragment pairs

DNA display of PNA-encoded libraries was used to pair fragments containing different phosphotyrosine surrogates with diverse triazoles. Microarray-based screening of the combinatorially paired fragment sets (62,500 combinations) against a prototypical phosphatase, PTP1B, was used to identify the fittest fragments. A focused library (10,000 members) covalently pairing identified fragments with linkers of different length and geometry was synthesized. Screening of the focused library against PTP1B and closely related TCPTP revealed orthogonal inhibitors. The selectivity of the identified inhibitors for PTP1B versus TCPT was confirmed by enzymatic inhibition assay.

Bidentate inhibitors of protein tyrosine phosphatases

SIGNIFICANCE

Protein tyrosine phosphatases (PTPs) are important enzymes that are involved in the regulation of cellular signaling. Evidence accumulated over the years has indicated that PTPs present exciting opportunities for drug discovery against diseases such as diabetes, cancer, autoimmune diseases, and tuberculosis. However, the highly conserved and partially positive charge of the catalytic sites of PTPs is a major challenge in the development of potent and highly selective PTP inhibitors.

RECENT ADVANCES

Here, we examine the strategy of developing bidentate inhibitors for selective inhibition of PTPs. Bidentate inhibitors are small-molecular-weight compounds with the ability to bind to both the active site and a non-conserved secondary phosphate binding site. This secondary phosphate binding site was initially discovered in protein tyrosine phosphatase 1B (PTP1B), and, hence, most of the bidentate inhibitors reported in this review are PTP1B inhibitors.

CRITICAL ISSUES

Although bidentate inhibition is a good strategy for developing potent and selective inhibitors, the cell membrane permeability and pharmacokinetic properties of the inhibitors are also important for successful drug development. In this review, we will also summarize the various efforts made toward the development of phosphotyrosine (pTyr) mimetics for increasing cellular permeability.

FUTURE DIRECTIONS

Even though the secondary phosphate binding site was initially found in PTP1B, structural data have shown that a secondary binding site can also be found in other PTPs, albeit with varying degrees of accessibility. Along with improvements in pTyr mimetics, we believe that the future will see an increase in the number of orally bioavailable bidentate inhibitors against the various classes of PTPs.

Fluorogenic probing of specific recognitions between sugar ligands and glycoprotein receptors on cancer cells by an economic graphene nanocomposite

Economical nanocomposites based on π-stacking of N-acetyl glycosyl rhodamine B to graphene oxide (GO) are simply prepared. These "sweet" GO-materials are proven to be admirable for the fluorogenic recognition of specific intercellular sugar-based ligand-glycoprotein receptor interactions of interest.

CuAAC click chemistry accelerates the discovery of novel chemical scaffolds as promising protein tyrosine phosphatases inhibitors

Protein tyrosine phosphatases (PTPs) are crucial regulators for numerous biological processes in nature. The dysfunction and overexpression of many PTP members have been demonstrated to cause fatal human diseases such as cancers, diabetes, obesity, neurodegenerative diseases and autoimmune disorders. In the past decade, considerable efforts have been devoted to the production of PTPs inhibitors by both academia and the pharmaceutical industry. However, there are only limited drug candidates in clinical trials and no commercial drugs have been approved, implying that further efficient discovery of novel chemical entities competent for inhibition of the specific PTP target in vivo remains yet a challenge. In light of the click-chemistry paradigm which advocates the utilization of concise and selective carbon-heteroatom ligation reactions for the modular construction of useful compound libraries, the Cu(I)-catalyzed azidealkyne 1,3-dipolar cycloaddition reaction (CuAAC) has fueled enormous energy into the modern drug discovery. Recently, this ingenious chemical ligation tool has also revealed efficacious and expeditious in establishing large combinatorial libraries for the acquisition of novel PTPs inhibitors with promising pharmacological profiles. We thus offer here a comprehensive review highlighting the development of PTPs inhibitors accelerated by the CuAAC click chemistry.

Discovery of a sensitive Cu(II)-cyanide "off-on" sensor based on new C-glycosyl triazolyl bis-amino acid scaffold

A new functional glycosyl peptidomimetic, featuring a C-glucosyl 1,4-dimethoxynaphthalene backbone in conjugation with two triazolyl phenylalanine moieties on its adjacent C3,4-positions, was readily synthesized via click chemistry. Primary optical measurements indicated that the fluorescence of the ester form of this probe (4) could be selectively quenched by Pb(2+). In contrast, the fluorescence intensity of its analog 5 with released carboxylic groups was uniquely diminished by Cu(2+) with remarkably enhanced sensitivity and selectivity. Moreover, subsequent addition of cyanide to the methanol solution of the resulting Cu(2+)-5 complex induced its fluorescence recovery with a nanomolar detection limit, which was two orders of magnitude smaller than the regulated concentration limit of CN(-) in drinking water. This suggests the promising applicability of C-glycosyl bis-triazolyl amino acid scaffold in the future design and exploration of sensitive "off-on" Cu(II)-cyanide chemosensors.

Regioselective synthesis of novel 3-thiazolidine acetic acid derivatives from glycosido ureides

A series of 3-thiazolidine acetic acid-2-(per-O-acetylglycosyl)-1'-imino-α-(substituted)-4-oxo ethyl ester derivatives (3a-t) were prepared via the reaction of substituted amino acid-N-[(per-O-acetylglycosylamino)thioxomethyl]-ethyl ester with ethyl bromoacetate. The crystal structure of 3-thiazolidine acetic acid-2-(2',3',4',6'-tetra-O-acetyl-β-D-galactoyranosyl)-1'-imino-α-methyl-4-oxo ethyl ester 3g and ¹H-¹³C HMBC (2D NMR experiments) measurements of 3-thiazolidine acetic acid-2-(2',3',4',6'-tetra-O-acetyl-β-D-galactopyranosyl)-1'-imino-α-(1-methylthio)ethyl-4-oxo ethyl ester 3j revealed the exclusive regioselectivity during the closure of these rings toward the N-2 position of the thiourea moiety. Furthermore, the crystal structure of compound 3g showed that the attack of N-1 was blocked by sugar ring owing to the steric effect. The bioactivity data suggested that compound 2e has mild anticancer activity.