Water-based carbodiimide mediated synthesis of polysaccharide-amino acid conjugates: Deprotection, charge and structural analysis.

We report here a one-step aqueous method for the synthesis of isolated and purified polysaccharide-amino acid conjugates. Two different types of amino acid esters: glycine methyl ester and L-tryptophan methyl ester, as model compounds for peptides, were conjugated to the polysaccharide carboxymethylcellulose (CMC) in water using carbodiimide at ambient conditions. Detailed and systematic pH-dependent charge titration and spectroscopy (infrared, nuclear magnetic resonance: 1H, 13C- DEPT 135, 1H- 13C HMBC/HSQC correlation), UV-vis, elemental and ninhydrin analysis provided solid and direct evidence for the successful conjugation of the amino acid esters to the CMC backbone via an amide bond. As the concentration of amino acid esters increased, a conjugation efficiency of 20-80% was achieved. Activated charcoal aided base-catalyzed deprotection of the methyl esters improved the solubility of the conjugates in water. The approach proposed in this work should have the potential to tailor the backbone of polysaccharides containing di- or tri-peptides.

Design, synthesis and biological evaluation of glycolamide, glycinamide, and ß-amino carbonyl 1,2,4-triazole derivatives as DPP-4 inhibitors.

Through modification of the skeleton of Sitagliptin and Vildagliptin, we successfully synthesized and built-up four series of 1,2,4-triazole derivatives, containing N,O-disubstituted glycolamide, N,N'-disubstituted glycinamide, ß-amino ester, and ß-amino amide as linkers, for the development of new dipeptidyl peptidase 4 (DPP-4) inhibitors. The synthetic strategy for glycolamides or glycinamides involved convenient two-steps reaction: functionalized transformation of 2-chloro-N-(2,4,5-triflurophenyl)acetamide 9 (hydroxylation or amination) and esterification or amidation of 1,2,4-triazole-3-carboxylic acid. On the other hand, the one-pot synthesis procedure, including substitution and deprotection, was developed for the preparation of ß-amino carbonyl 1,2,4-triazoles from (1H-1,2,4-triazol-3-yl)methanol 12 or (1H-1,2,4-triazol-3-yl)methanamine 13 and Boc-(R)-3-amino-4-(2,4,5-trifluoro-phenyl)-butyric acid 14. All of glycolamides, glycinamides, and ß-amino carbonyl 1,2,4-triazoles were also evaluated against DPP-4 inhibitory activity. Based on the SAR study of DPP-4 inhibitory capacity, ß-amino ester 5n and ß-amino amide 1,2,4-triazoles 6d and 6p possessed the significant inhibition of DPP-4 (IC50 < 51.0 nM), particularly for compound 6d (IC50 = 34.4 nM). The selectivity evaluation indicated compound 5n and 6p had excellent selectivity over QPP, DPP-8, and DPP-9. In addition, the docking results revealed compounds 5n and 6p provided stronger π-π stacking interaction with residue Phe357 than 1,5-disubstituted 1,2,4-triazole 6d and Sitagliptin 1. In summary, compounds 5n and 6p could be promising lead compounds for further development of DPP-4 inhibitor.

Ni-catalyzed asymmetric hydrogenation of N-aryl imino esters for the efficient synthesis of chiral α-aryl glycines.

Chiral α-aryl glycines play a key role in the preparation of some bioactive products, however, their catalytic asymmetric synthesis is far from being satisfactory. Herein, we report an efficient nickel-catalyzed asymmetric hydrogenation of N-aryl imino esters, affording chiral α-aryl glycines in high yields and enantioselectivities (up to 98% ee). The hydrogenation can be conducted on a gram scale with a substrate/catalyst ratio of up to 2000. The obtained chiral N-p-methoxyphenyl α-aryl glycine derivatives are not only directly useful chiral secondary amino acid esters but can also be easily deprotected by treatment with cerium ammonium nitrate for further transformations to several widely used molecules including drug intermediates and chiral ligands. Formation of a chiral Ni-H species in hydrogenation is detected by 1H NMR. Computational results indicate that the stereo selection is determined during the approach of the substrate to the catalyst.

Efficient Method for the Concentration Determination of Fmoc Groups Incorporated in the Core-Shell Materials by Fmoc-Glycine.

In this paper, we described the synthesis procedure of TiO2@SiO2 core-shell modified with 3-(aminopropyl)trimethoxysilane (APTMS). The chemical attachment of Fmoc-glycine (Fmoc-Gly-OH) at the surface of the core-shell structure was performed to determine the amount of active amino groups on the basis of the amount of Fmoc group calculation. We characterized nanostructures using various methods: transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) to confirm the modification effectiveness. The ultraviolet-visible spectroscopy (UV-vis) measurement was adopted for the quantitative determination of amino groups present on the TiO2@SiO2 core-shell surface by determination of Fmoc substitution. The nanomaterials were functionalized by Fmoc-Gly-OH and then the fluorenylmethyloxycarbonyl (Fmoc) group was cleaved using 20% (v/v) solution of piperidine in DMF. This reaction led to the formation of a dibenzofulvene-piperidine adduct enabling the estimation of free Fmoc groups by measurement the maximum absorption at 289 and 301 nm using UV-vis spectroscopy. The calculations of Fmoc loading on core-shell materials was performed using different molar absorption coefficient: 5800 and 6089 dm3 × mol-1 × cm-1 for λ = 289 nm and both 7800 and 8021 dm3 × mol-1 × cm-1 for λ = 301 nm. The obtained results indicate that amount of Fmoc groups present on TiO2@SiO2-(CH2)3-NH2 was calculated at 6 to 9 µmol/g. Furthermore, all measurements were compared with Fmoc-Gly-OH used as the model sample.

Organic Reaction Monitoring of a Glycine Derivative Using Signal Amplification by Reversible Exchange-Hyperpolarized Benchtop Nuclear Magnetic Resonance Spectroscopy.

Currently, signal amplification by reversible exchange (SABRE) using para-hydrogen is an attractive method of hyperpolarization for overcoming the sensitivity problems of nuclear magnetic resonance (NMR) spectroscopy. Additionally, SABRE, using the spin order of para-hydrogen, can be applied in reaction monitoring processes for organic chemistry reactions where a small amount of reactant exists. The organic reaction monitoring system created by integrating SABRE and benchtop NMR is the ideal combination for monitoring a reaction and identifying the small amounts of materials in the middle of the reaction. We used a laboratory-built setup, prepared materials by synthesis, and showed that the products obtained by esterification of glycine were also active in SABRE. The products, which were synthesized esterified glycine with nicotinoyl chloride hydrochloride, were observed with a reaction monitoring system. The maximum SABRE enhancement among them (approximately 147-fold) validated the use of this method. This study is the first example of the monitoring of this organic reaction by SABRE and benchtop NMR. It will open new possibilities for applying this system to many other organic reactions and also provide more fruitful future applications such as drug discovery and mechanism study.

The Synthesis and Anti-tumour Properties of Poly Ethoxy Ethyl Glycinamide (PEE-G) Scaffolds with Multiple PD-1 Peptides Attached.

Multivalent structures can provide multiple interactions at a target site and improve binding affinity. The multivalent presentation of the anti-tumour heptapeptide, SNTSESF, was investigated. This peptide's activity has been attributed to blockade of the PD-1 receptor-mediated signalling pathway. Two and four peptide units were conjugated to poly ethoxy ethyl glycinamide (PEE-G) scaffolds to prepare high-purity products. These conjugates and the peptide were examined in a mouse model implanted with GL261 tumours that indicated that presenting more than two copies of peptide SNTSESF on the dendritic scaffold does not increase anti-tumour activity per peptide. The fluorescent labelled peptide and most active multivalent peptide conjugate were therefore screened for their interaction with the human PD-L1 protein in a fluorescence polarisation assay. No indication of a specific SNTSESF peptide/PD-L1 interaction was observed. This finding was further supported by a molecular modelling binding study.

Pathway from N-Alkylglycine to Alkylisonitrile Catalyzed by Iron(II) and 2-Oxoglutarate-Dependent Oxygenases.

N-alkylisonitrile, a precursor to isonitrile-containing lipopeptides, is biosynthesized by decarboxylation-assisted -N≡C group (isonitrile) formation by using N-alkylglycine as the substrate. This reaction is catalyzed by iron(II) and 2-oxoglutarate (Fe/2OG) dependent enzymes. Distinct from typical oxygenation or halogenation reactions catalyzed by this class of enzymes, installation of the isonitrile group represents a novel reaction type for Fe/2OG enzymes that involves a four-electron oxidative process. Reported here is a plausible mechanism of three Fe/2OG enzymes, Sav607, ScoE and SfaA, which catalyze isonitrile formation. The X-ray structures of iron-loaded ScoE in complex with its substrate and the intermediate, along with biochemical and biophysical data reveal that -N≡C bond formation involves two cycles of Fe/2OG enzyme catalysis. The reaction starts with an FeIV -oxo-catalyzed hydroxylation. It is likely followed by decarboxylation-assisted desaturation to complete isonitrile installation.

Synthesis of N-(6-[18F]Fluoropyridin-3-yl)glycine as a potential renal PET agent.

OBJECTIVE: Given the requirements of high sensitivity and spatial resolution, the development of new positron emission tomography (PET) agents is required for PET renography. The objective of this study was to investigate a new fluorine-18 labeled hippurate analogue of picolinamide, N-(6-[18F]Fluoropyridin-3-yl)glycine, as a new renal PET agent for evaluating renal function. METHODS: N-(6-[18F]Fluoropyridin-3-yl)glycine was prepared via a two-step reaction, including the nucleophilic substitution reaction of Br with 18F using methyl 2-(6-bromonicotinamido)acetate as a precursor followed the hydrolysis with sodium hydroxide and purification by preparative-HPLC. The in vitro and in vivo stability were determined using HPLC, and the plasma protein binding (PPB) and erythrocyte uptake of N-(6-[18F]Fluoropyridin-3-yl)glycine were determined using blood collected from healthy rats at 5 min post-injection. Biodistribution and dynamic micro-PET/CT imaging studies were conducted in healthy rats. RESULTS: N-(6-[18F]Fluoropyridin-3-yl)glycine was prepared within 45 min with an uncorrected radiochemical yield of 24.5 ±â€¯6.7% (n = 6, based on [18F]F-) and a radiochemical purity of >98%. N-(6-[18F]Fluoropyridin-3-yl)glycine demonstrated good stability both in vitro and in vivo. The results of the biodistribution and dynamic micro-PET/CT imaging studies in normal rats indicated that N-(6-[18F]Fluoropyridin-3-yl)glycine was rapidly and exclusively excreted via the renal-urinary pathway. CONCLUSION: N-(6-[18F]Fluoropyridin-3-yl)glycine is has been shown to be a promising renal PET agent and warrants further evaluation of renal function.

Semisynthesis of Ubiquitin and SUMO-Rhodamine 110-Glycine through Aminolysis of Boc-Protected Thioester Counterparts.

Ubiquitin (Ub)-based fluorescent reagents are crucial to explore the activity of deubiquitinases (DUBs). Ub-Rho110-G is one of the preferred tools, whereas the current synthetic route is time-consuming. Here, we report a new semisynthetic strategy to produce Ub-Rho110-G through direct aminolysis of Boc-protected Ub-Mesna using bisglycyl-rhodamine 110. We also applied this strategy to synthesize active SUMO2-Rho110-G for the first time. Biochemical analysis demonstrated that semisynthetic Ub or SUMO-Rho110-G can be effectively used for the detection of the activity of DUBs or SUMO-specific enzymes.

Identification of small peptides and glycinamide that inhibit melanin synthesis using a positional scanning synthetic peptide combinatorial library.

BACKGROUND: Antimelanogenic peptides are potentially useful to treat hyperpigmentation, but many peptides have limited application because of high cost and/or low activity. OBJECTIVES: To identify small and potent peptide inhibitors of cellular melanin synthesis that are useful for cosmetic and medical applications. METHODS: A positional scanning synthetic tetrapeptide combinatorial library was used for screening of potentially active peptides. Antimelanogenic activities of the peptide pools and individual peptides were evaluated in B16-F10 melanoma cells and human epidermal melanocytes treated with alpha-melanocyte-stimulating hormone (α-MSH). RESULTS: Predicted active tetrapeptide sequences were R-(F/L)-(C/W)-(G/R)-NH2 . Of the individual tetrapeptides tested, D3 (RFWG-NH2 ) and D5 (RLWG-NH2 ) exhibited high antimelanogenic activities. Tetrapeptide D9 (FRWG-NH2 ) with a sequence identical to that of a portion of α-MSH also showed antimelanogenic activity. Of the tripeptides tested, E5 (FWG-NH2 ), E6 (LWG-NH2 ) and E7 (RWG-NH2 ) were relatively more active. Dipeptide F1 (WG-NH2 ) and monopeptide G1 (G-NH2 , glycinamide) retained activity, but G2 (Ac-G-NH2 ) and G3 (glycine) did not. The antimelanogenic activities of peptides D3, E5, F1 and G1 were verified in α-MSH-stimulated human epidermal melanocytes. Commercially available G-NH2 ·HCl suppressed the phosphorylation levels of cAMP-responsive element binding protein, protein levels of microphthalmia-associated transcription factor and tyrosinase, l-tyrosine hydroxylase activity of tyrosinase, and the melanin levels in stimulated cells. CONCLUSIONS: Small peptides, including glycinamide and tryptophanyl glycinamide, are potent antimelanogenic agents with potential value for the treatment of skin hyperpigmentation.

Flexibility of small molecular CD4 mimics as HIV entry inhibitors.

CD4 mimics such as YIR-821 and its derivatives are small molecules which inhibit the interaction between the Phe43 cavity of HIV-1 gp120 with host CD4, an interaction that is involved in the entry of HIV to cells. Known CD4 mimics generally possess three structural features, an aromatic ring, an oxalamide linker and a piperidine moiety. We have shown previously that introduction of a cyclohexyl group and a guanidine group into the piperidine moiety and a fluorine atom at the meta-position of the aromatic ring leads to a significant increase in the anti-HIV activity. In the current study, the effects of conformational flexibility were investigated by introduction of an indole-type group in the junction between the oxalamide linker and the aromatic moiety or by replacement of the oxalamide linker with a glycine linker. This led to the development of compounds with high anti-HIV activity, showing the importance of the junction region for the expression of high anti-HIV activity. The present data are expected to be useful in the future design of novel CD4 mimic molecules.

In the quest for new targets for pathogen eradication: the adenylosuccinate synthetase from the bacterium Helicobacter pylori.

Adenylosuccinate synthetase (AdSS) is an enzyme at regulatory point of purine metabolism. In pathogenic organisms which utilise only the purine salvage pathway, AdSS asserts itself as a promising drug target. One of these organisms is Helicobacter pylori, a wide-spread human pathogen involved in the development of many diseases. The rate of H. pylori antibiotic resistance is on the increase, making the quest for new drugs against this pathogen more important than ever. In this context, we describe here the properties of H. pylori AdSS. This enzyme exists in a dimeric active form independently of the presence of its ligands. Its narrow stability range and pH-neutral optimal working conditions reflect the bacterium's high level of adaptation to its living environment. Efficient inhibition of H. pylori AdSS with hadacidin and adenylosuccinate gives hope of finding novel drugs that aim at eradicating this dangerous pathogen.

Ethynylglycine synthon, a useful precursor for the synthesis of biologically active compounds: an update. Part II: synthetic uses of ethynylglycine synthon.

The ethynylglycine synthon {(R)-2,2-dimethyl-3-(tert-butoxycarbonyl)-4-ethynyl-oxazolidine} is a chiral compound with valuable synthetic interest. An update (covering literature from 2005 to 2017) on the different synthetic utilities is reviewed and discussed.

Design, synthesis, and evaluation of novel l-phenylglycine derivatives as potential PPARγ lead compounds.

In accordance with the structural characteristics of thiazolidinedione drugs and highly bioactive tyrosine derivatives, we tentatively designed the l-phenylglycine derivatives TM1 and TM2 based on basic principles of drug design and then synthesized them. The in vitro screening of peroxisome proliferator-activated receptor gamma (PPARγ) activated activity, α-glucosidase inhibitory and dipeptidyl peptidase-4 inhibitory activities showed that the novel molecule M5 had efficient PPAR response element (PPRE) activated activity (PPRE relative activity 105.04% at 10 µg·mL-1 compared with the positive control pioglitazone, with 100% activity). Therefore, M5 was selected as the hit compound from which the TM3 and TM4 series of compounds were further designed and synthesized. Based on the PPRE relative activities of TM3 and TM4, we discovered another new molecule, TM4h, which had the strongest PPRE relative activity (120.42% at 10 µg·mL-1). In addition, the concentration-dependent activity of the highly active compounds was determined by assaying their half-maximal effective concentration (EC50) values. The molecular physical parameter calculation and the molecular toxicity prediction were used to theoretically evaluate the lead-likeness and safety of the active compounds. In conclusion, we identified a potential PPARγ lead molecule and developed a tangible strategy for antidiabetic drug development.

In-vitro evaluation and in-silico studies applied on newly synthesized amide derivatives of N-phthaloylglycine as Butyrylcholinesterase (BChE) inhibitors.

Amide derivatives of N-phthaloylglycine were synthesized under Schotten Baumann reaction condition. The structures of synthesized compounds (4a-d) were characterized by using FTIR, 1HNMR and EI-MS. The compounds were evaluated for their in-vitro Butyrylcholinesterase inhibition and all of them exhibited good activity against this enzyme. Compound 4a (IC50 = 6.5 ±â€¯0.1) was found to be most potent compared with the reference compound Galantamine (IC50 = 6.6 ±â€¯0.00038) and the other compounds (4b,4c,4d) were also possess that activity and hence can be employed for the discovery of lead compounds against Alzheimer's disease. The depth analysis of the binding mechanism of these newly synthesized compounds inside the binding gorge of BChE, an in silico technique, molecular docking was performed. All the compounds were found to be well accommodated within the binding pocket of BChE. Compounds 4a, 4b and 4c showed hydrogen bonding interaction with binding site residue TYR332. Moreover, hydrophobic and π-π interaction assisted the compounds to attain their enzyme inhibitory activity. These theoretical studies showed significant correlation with experimental results.

Metabolic engineering of Corynebacterium glutamicum for production of sunscreen shinorine.

Ultraviolet-absorbing chemicals are useful in cosmetics and skin care to prevent UV-induced skin damage. We demonstrate here that heterologous production of shinorine, which shows broad absorption maxima in the UV-A and UV-B region. A shinorine producing Corynebacterium glutamicum strain was constructed by expressing four genes from Actinosynnema mirum DSM 43827, which are responsible for the biosynthesis of shinorine from sedoheptulose-7-phosphate in the pentose phosphate pathway. Deletion of transaldolase encoding gene improved shinorine production by 5.2-fold. Among the other genes in pentose phosphate pathway, overexpression of 6-phosphogluconate dehydrogenase encoding gene further increased shinorine production by 60% (19.1 mg/L). The genetic engineering of the pentose phosphate pathway in C. glutamicum improved shinorine production by 8.3-fold in total, and could be applied to produce the other chemicals derived from sedoheptulose-7-phosphate.

Design, Synthesis, and SAR of Novel 2-Glycinamide Cyclohexyl Sulfonamide Derivatives against Botrytis cinerea.

N-(2-trifluoromethyl-4-chlorophenyl)-2-oxocyclohexyl sulfonamide (chesulfamide) is in the limelight as a novel fungicide, and has fungicidal activity against Botrytis cinerea. For exploring more novel structures, 33 new compounds were synthesized by N-alkylation and acid-amine coupling reactions with chesulfamide as the core moiety, and their structures were characterized and established by ¹H-NMR, 13C-NMR, MS, and elemental analysis. The structure of (1R,2S)-2-(2-(N-(4-chloro-2-trifluoromethylphenyl)sulfamoyl)-cyclohexylamino)-N-(2-trifluoromethylphenyl) acetamide (II-19) was defined by X-ray single crystal diffraction. The in vivo and in vitro fungicidal activities against B. cinerea were evaluated. The bioassay results of mycelial growth demonstrated that most compounds exhibited excellent inhibitory activity against B. cinerea at 50 µg mL-1, and 7 compounds showed lower EC50 values than boscalid (EC50 = 4.46 µg mL-1) against B. cinerea (CY-09). In cucumber pot experiment, the inhibitory rates of four compounds (II-4, II-5, II-12, and II-13) against B. cinerea were 90.48, 93.45, 92.86, and 91.07, which were better than cyprodinil (88.69%), the best performing of all controls. In tomato pot experiment, the control efficacy of two analogs (II-8 and II-15) were 87.98 and 87.97% at 200 µg mL-1, which were significantly higher than boscalid (78.10%). Most compounds have an excellent fungicidal effect on B. cinerea, with potential as a lead compound for developing new pesticides.

A route to diastereomerically pure phenylglycine thioester peptides: crucial intermediates for investigating glycopeptide antibiotic biosynthesis.

Non-ribosomal peptides contain an array of amino acid building blocks that can present challenges for the synthesis of important intermediates. Here, we report the synthesis of glycopeptide antibiotic (GPA) thioester peptides that retains the crucial stereochemical purity of the terminal phenylglycine residue, which we show is essential for the enzymatic GPA cyclisation cascade.

An efficient and practical synthesis of formylglycinamide ribonucleotide (FGAR).

An efficient five-step synthetic route for multigram-scale preparation of formylglycinamide ribonucleotide (FGAR) from peracetylated ß-d-ribofuranosyl azide has been developed.

Effect of lipophilicity of amylamine and amylglycine ligands on biological activity of new anticancer cisplatin analog.

Investigation of side effects and solubility of anticancer drugs is a major challenge in chemotherapy science. Thus, design and synthesis of cisplatin analogs with higher lipophilicity as novel water-soluble anticancer drugs is valuable. In this work, two new Pt(II) complexes were synthesized with formula cis-[Pt(NH3)2(amylgly)]NO3 and cis-[Pt(amylamine)2(amylgly)]NO3, where gly is penthyl glycine as an amino acid. The new compounds were synthesized and extensively characterized using analytical techniques; spectroscopic methods, and conductivity measurement. The anticancer activity of synthesized complexes was investigated against colon cancer cell line HCT116 using MTT assay and results showed excellent anticancer activity with Cc50 values of 36 and 270 M after 24-h incubation time for cis-[Pt(NH3)2(amylgly)]NO3 and cis-[Pt(NH2-amyl)2(amylgly)]NO3, respectively; which is lower than that for cisplatin. These complexes were also interacted with highly polymerized calf thymus DNA and the binding mode of the complexes to CT-DNA was evaluated by fluorescence, circular dichroism, and UV spectroscopy. The calculation of binding and thermodynamic of Pt(II) complexes with CT-DNA can provide deeper insight into mechanism of the action of these types of complexes with nucleic acids. So, thermodynamic parameters were also determined according to isothermal titration. In comparison with cis-[Pt(NH3)2(amylgly)]NO3 in DNA interaction, the result show that cis-[Pt(NH2-amyl)2(amylgly)]NO3 has higher affinity with binding constant Kf = 8.72 mM to CT-DNA. The results indicate that cis-[Pt(amylamine)2(amylgly)]NO3 with large and bulky aliphatic group bind to CT-DNA by different modes and covalent and groove bindings were preferred mode of interaction with DNA.