EGCG-like non-competitive inhibitor of DYRK1A rescues cognitive defect in a down syndrome model.

Overexpression of the chromosome 21 DYRK1A gene induces morphological defects and cognitive impairments in individuals with Down syndrome (DS) and in DS mice models. Aging neurons of specific brain regions of patients with Alzheimer's disease, DS and Pick's disease have increased DYRK1A immunoreactivity suggesting a possible association of DYRK1A with neurofibrillary tangle pathology. Epigallocatechin-3-gallate (EGCG) displays appreciable inhibition of DYRK1A activity and, contrary to all other published inhibitors, EGCG is a non-competitive inhibitor of DYRK1A. Prenatal exposure to green tea polyphenols containing EGCG protects from brain defects induced by overexpression of DYRK1A. In order to produce more robust and possibly more active analogues of the natural compound EGCG, here we synthetized new EGCG-like molecules with several structural modifications to the EGCG skeleton. We replaced the ester boun of EGCG with a more resistant amide bond. We also replaced the oxygen ring by a methylene group. And finally, we positioned a nitrogen atom within this ring. The selected compound was shown to maintain the non-competitive property of EGCG and to correct biochemical and behavioral defects present in a DS mouse model. In addition it showed high stability and specificity.

Azetidinimines as a novel series of non-covalent broad-spectrum inhibitors of ß-lactamases with submicromolar activities against carbapenemases KPC-2 (class A), NDM-1 (class B) and OXA-48 (class D).

The occurrence of resistances in Gram negative bacteria is steadily increasing to reach extremely worrying levels and one of the main causes of resistance is the massive spread of very efficient ß-lactamases which render most ß-lactam antibiotics useless. Herein, we report the development of a series of imino-analogues of ß-lactams (namely azetidinimines) as efficient non-covalent inhibitors of ß-lactamases. Despite the structural and mechanistic differences between serine-ß-lactamases KPC-2 and OXA-48 and metallo-ß-lactamase NDM-1, all three enzymes can be inhibited at a submicromolar level by compound 7dfm, which can also repotentiate imipenem against a resistant strain of Escherichia coli expressing NDM-1. We show that 7dfm can efficiently inhibit not only the three main clinically-relevant carbapenemases of Ambler classes A (KPC-2), B (NDM-1) and D (OXA-48) with Ki's below 0.3 µM, but also the cephalosporinase CMY-2 (class C, 86% inhibition at 10 µM). Our results pave the way for the development of a new structurally original family of non-covalent broad-spectrum inhibitors of ß-lactamases.

Synthesis of Rottlerone Analogues and Evaluation of Their α-Glucosidase and DPP-4 Dual Inhibitory and Glucose Consumption-Promoting Activity.

Our previous study found that desmethylxanthohumol (1) inhibited α-glucosidase in vitro. Recently, further investigations revealed that dehydrocyclodesmethylxanthohumol (2) and its dimer analogue rottlerone (3) exhibited more potent α-glucosidase inhibitory activity than 1. The aim of this study was to synthesize a series of rottlerone analogues and evaluate their α-glucosidase and DPP-4 dual inhibitory activity. The results showed that compounds 4d and 5d irreversibly and potently inhibited α-glucosidase (IC50 = 0.22 and 0.12 µM) and moderately inhibited DPP-4 (IC50 = 23.59 and 26.19 µM), respectively. In addition, compounds 4d and 5d significantly promoted glucose consumption, with the activity of 5d at 0.2 µM being comparable to that of metformin at a concentration of 1 mM.

Rhodium-catalyzed iminoiodane-mediated oxyamidation studies of 5-vinyluracil derivatives using aryl and alkyl sulfamates.

The dirhodium tetraacetate-catalyzed iminoiodane-mediated reaction of 1,3-dimethyl-5-vinyluracil with phenyl sulfamate provided a high yield of 5-(1-acetyl-2-phenylsulfamoyl)ethyluracil via regioselective nucleophilic ring opening by acetate anion of the transiently formed 5-(1,2)-N-phenylsulfonylaziridine intermediate. This 1,2-oxyamidation reaction was found to be general for a variety of aryl- and alkylsulfamates as well as for various 1,3-dialkyl-5-vinyluracil derivatives. Addition of an alcohol to the reaction mixture allowed formation of the corresponding 1-alkoxy products. A selection of the substituted uracil derivatives prepared by this procedure was evaluated for cytotoxic activities in HCT-116 and HepG2 cancer cell lines and showed either no or modest activities. Further evaluation for α-glucosidase inhibition revealed that compounds 15ca and 15da were more active than acarbose, the reference inhibitor. This methodology thus allows efficient preparation of highly functionalized uracil derivatives thereby providing a synthetic route to novel compounds with potentially useful biological activities.

Synthesis of tetracyclic oxindoles and evaluation of their α-glucosidase inhibitory and glucose consumption-promoting activity.

A series of tetracyclic oxindole derivatives was synthesized by asymmetric 1, 3-dipole reaction in 2-4 steps in 57-86% overall yields. These compounds were evaluated for α-glucosidase inhibitory and glucose consumption-promoting activity in vitro. Compound 4l competitively and reversibly inhibited α-glucosidase (IC50 = 3.64 µM) with activity 14-fold higher than that of acarbose. Docking analysis substantiated these findings. In addition, compound 4l exhibited significant glucose consumption promoting activity at 1 µM.

Iodine(III)-mediated halogenations of acyclic monoterpenoids.

Five different halofunctionalizations of acyclic monoterpenoids were performed using a combination of a hypervalent iodine(III) reagent and a halide salt. In this manner, the dibromination, the bromo(trifluoro)acetoxylation, the bromohydroxylation, the iodo(trifluoro)acetoxylation or the ene-type chlorination of the distal trisubstituted double bond occurred with excellent selectivity and moderate to good yields.

Synthesis & α-glucosidase inhibitory & glucose consumption-promoting activities of flavonoid-coumarin hybrids.

AIM: The research of novel and potent antidiabetic agents is urgently needed for the control of the exploding diabetic population. We previously reported the synthesis and antidiabetic activity of natural 8-(6"-umbelliferyl)-apigenin (1), but its antidiabetic targets are not known. Therefore, four series of derivatives were synthesized and evaluated for their antidiabetic activities. Results & methodology: Compounds (5a) and (14a) were identified as new α-glucosidase and α-amylase dual inhibitors. The kinetic analysis of the most potent α-glucosidase inhibitor of each series of compounds revealed that they inhibited α-glucosidase in irreversible modes. In addition, compounds (5a) and (14a) showed potent glucose consumption-promoting activity. CONCLUSION: Compounds (5a) and (14a) could be regarded as promising starting points for the development of antidiabetic candidates.

DYRK1A inhibition and cognitive rescue in a Down syndrome mouse model are induced by new fluoro-DANDY derivatives.

Inhibition of DYRK1A kinase, produced by chromosome 21 and consequently overproduced in trisomy 21 subjects, has been suggested as a therapeutic approach to treating the cognitive deficiencies observed in Down syndrome (DS). We now report the synthesis and potent DYRK1A inhibitory activities of fluoro derivatives of 3,5-di(polyhydroxyaryl)-7-azaindoles (F-DANDYs). One of these compounds (3-(4-fluorophenyl)-5-(3,4-dihydroxyphenyl)-1H-pyrrolo[2,3-b]pyridine, 5a) was selected for in vivo studies of cognitive rescuing effects in a standard mouse model of DS (Ts65Dn line). Using the Morris water maze task, Ts65Dn mice treated i.p. with 20 mg/kg of 5a performed significantly better than Ts65Dn mice treated with placebo, confirming the promnesiant effect of 5a in the trisomic mice. Overall, these results demonstrate for the first time that selective and competitive inhibition of DYRK1A kinase by the F-DANDY derivative 5a may provide a viable treatment strategy for combating the memory and learning deficiencies encountered in DS.

Ketenimines Generated from Ynamides: Versatile Building Blocks for Nitrogen-Containing Scaffolds.

Using ynamides as readily available starting materials, a single step can generate highly reactive ketenimines, which can then undergo a variety of transformations. The choice of the method for generating the ketenimine dictates the outcome of the reaction that can, moreover, be precisely steered through minor variations of the starting material. This Concept gives an overview of the different existing methodologies for this objective, showcasing the diverse nitrogen-containing frameworks that can be obtained by this highly versatile strategy.

Chemodivergent, Tunable, and Selective Iodine(III)-Mediated Bromo-Functionalizations of Polyprenoids.

Mild oxidation of bromides by iodine(III) reagents generated active electrophilic bromination species that were reacted with polyprenoids. By simple and minor variations of an I(III)/Br combination, the reactivity could be selectively steered toward dibromination, oxybromination, or bromocyclization, giving access to a wide array of brominated motifs.

Synthesis of 6-hydroxyaurone analogues and evaluation of their α-glucosidase inhibitory and glucose consumption-promoting activity: Development of highly active 5,6-disubstituted derivatives.

A series of 6-hydroxyaurones and their analogues have been synthesized and evaluated for their in vitro α-glucosidase inhibitory and glucose consumption-promoting activity. These compounds exhibited varying degrees of α-glucosidase inhibitory activity, 11 of them showing higher potency than that of the control standard acarbose (IC50=50.30µM). Surprisingly, analogues devoid of a substituent at C-2 but having an aryl group at C-5 were found to be highly active (e.g., 7f, IC50=9.88µM). Docking analysis substantiated these findings. The kinetic analysis of compound 7f, the most potent α-glucosidase inhibitor of this study, revealed that it inhibited α-glucosidase in an irreversible and mixed competitive mode. In addition, compounds 7f and 10c exhibited significant glucose consumption promoting activity at 1µM.

Base-Mediated Generation of Ketenimines from Ynamides: Direct Access to Azetidinimines by an Imino-Staudinger Synthesis.

Ynamides were used as precursors for the in situ generation of highly reactive ketenimines that could be trapped with imines in a [2+2] cycloaddition. This imino-Staudinger synthesis led to a variety of imino-analogs of ß-lactams, namely azetidinimines (20 examples), that could be further functionalized through a broad range of transformations.

A direct label-free MALDI-TOF mass spectrometry based assay for the characterization of inhibitors of protein lysine methyltransferases.

Histone lysine methylation is associated with essential biological functions like transcription activation or repression, depending on the position and the degree of methylation. This post-translational modification is introduced by protein lysine methyltransferases (KMTs) which catalyze the transfer of one to three methyl groups from the methyl donor S-adenosyl-L-methionine (AdoMet) to the amino group on the side chain of lysines. The regulation of protein lysine methylation plays a primary role not only in the basic functioning of normal cells but also in various pathologies and KMT deregulation is associated with diseases including cancer. These enzymes are therefore attractive targets for the development of new antitumor agents, and there is still a need for direct methodology to screen, identify, and characterize KMT inhibitors. We report here a simple and robust in vitro assay to quantify the enzymatic methylation of KMT by MALDI-TOF mass spectrometry. Following this protocol, we can monitor the methylation events over time on a peptide substrate. We detect in the same spectrum the modified and unmodified substrates, and the ratios of both signals are used to quantify the amount of methylated substrate. We first demonstrated the validity of the assay by determining inhibition parameters of two known inhibitors of the KMT SET7/9 ((R)-PFI-2 and sinefungin). Next, based on structural comparison with these inhibitors, we selected 42 compounds from a chemical library. We applied the MALDI-TOF assay to screen their activity as inhibitors of the KMT SET7/9. This study allowed us to determine inhibition constants as well as kinetic parameters of a series of SET7/9 inhibitors and to initiate a structure activity discussion with this family of compounds. This assay is versatile and can be easily adapted to other KMT substrates and enzymes as well as automatized.

Identification of cancer chemopreventive isothiocyanates as direct inhibitors of the arylamine N-acetyltransferase-dependent acetylation and bioactivation of aromatic amine carcinogens.

Aromatic amines (AAs) are chemicals of industrial, pharmacological and environmental relevance. Certain AAs, such as 4-aminobiphenyl (4-ABP), are human carcinogens that require enzymatic metabolic activation to reactive chemicals to form genotoxic DNA adducts. Arylamine N-acetyltransferases (NAT) are xenobiotic metabolizing enzymes (XME) that play a major role in this carcinogenic bioactivation process. Isothiocyanates (ITCs), including benzyl-ITC (BITC) and phenethyl-ITC (PEITC), are phytochemicals known to have chemopreventive activity against several aromatic carcinogens. In particular, ITCs have been shown to modify the bioactivation and subsequent mutagenicity of carcinogenic AA chemicals such as 4-ABP. However, the molecular and biochemical mechanisms by which these phytochemicals may modulate AA carcinogens bioactivation and AA-DNA damage remains poorly understood. This manuscript provides evidence indicating that ITCs can decrease the metabolic activation of carcinogenic AAs via the irreversible inhibition of NAT enzymes and subsequent alteration of the acetylation of AAs. We demonstrate that BITC and PEITC react with NAT1 and inhibit readily its acetyltransferase activity (k(i) = 200 M(-1).s(-1) and 66 M(-1).s(-1) for BITC and PEITC, respectively). Chemical labeling, docking approaches and substrate protection assays indicated that inhibition of the acetylation of AAs by NAT1 was due to the chemical modification of the enzyme active site cysteine. Moreover, analyses of AAs acetylation and DNA adducts in cells showed that BITC was able to modulate the endogenous acetylation and bioactivation of 4-ABP. In conclusion, we show that direct inhibition of NAT enzymes may be an important mechanism by which ITCs exert their chemopreventive activity towards AA chemicals.

Mallotojaponins B and C: Total Synthesis, Antiparasitic Evaluation, and Preliminary SAR Studies.

The first total syntheses of mallotojaponin B and C as well as several analogues have been achieved. Biological evaluation of the synthesized compounds against Plasmodium falciparum and Trypanosoma brucei have also been carried out.

Design and synthesis of calindol derivatives as potent and selective calcium sensing receptor agonists.

We report the first comprehensive structure-activity study of calindol (4, (R)-N-[(1H-indol-2-yl)methyl]-1-(1-naphthyl)ethanamine), a positive allosteric modulator, or calcimimetic, of the calcium sensing receptor (CaSR). While replacement of the naphthyl moiety of calindol by other aromatic groups (phenyl, biphenyl) was largely detrimental to calcimimetic activity, incorporation of substituents on the 4, 5 or 7 position of the indole portion of calindol was found to provide either equipotent derivatives compared to calindol (e.g., 4-phenyl, 4-hydroxy, 5-hydroxycalindol 44, 52, 53) or, in the case of 7-nitrocalindol (51), a 6-fold more active calcimimetic displaying an EC50 of 20nM. Unlike calindol, the more active CaSR calcimimetics were shown not to act as antagonists of the closely related GPRC6A receptor, suggesting a more selective profile for these new analogues.

Halocyclization of Unsaturated Guanidines Mediated by Koser's Reagent and Lithium Halides.

The synthesis of halogenated cyclic guanidines through iodine(III)-mediated umpolung of halide salts is described. Cyclic guanidines of various sizes can be obtained with generally excellent regioselectivities through either a chloro- or a bromocyclization, using Koser's reagent and the corresponding lithium salt.

Iodine(III)-Mediated Diazidation and Azido-oxyamination of Enamides.

In this study we demonstrate that the combination of bis(tert-butylcarbonyloxy)iodobenzene and lithium azide in acetonitrile allows the diazidation of various enamide substrates. The azido-oxyamination of the same substrates can be carried out in the presence of 2,2,6,6-tetramethylpiperidine N-oxide (TEMPO). Control experiments strongly suggest that this latter process occurs through a shift in nature of the in situ generated electrophilic species from a radical to a cation. Finally, the versatility of the novel compounds synthesized was also assessed by running various selective reactions on them.

GABA(A) receptor subtype-selectivity of novel bicuculline derivatives.

GABA(A) receptors are the major inhibitory neurotransmitter receptors in the central nervous system and are targets of clinically important drugs modulating GABA induced ion flux by interacting with distinct allosteric binding sites. ROD 185 is a previously investigated structural analogue of the GABA site antagonist bicuculline, and a positive allosteric modulator acting via the benzodiazepine binding site. Here, we investigated 13 newly synthesized structural analogues of ROD 185 for their interaction with rat GABA(A) receptors. Using [(3)H]flunitrazepam binding assays, we identified four compounds exhibiting a higher affinity for the benzodiazepine binding site than ROD 185. Two electrode voltage clamp electrophysiology at recombinant GABA(A) receptors indicated that most of these compounds positively modulated GABA-induced currents at these receptors. Additionally, these experiments revealed that this compound class not only interacts with the benzodiazepine binding site at αßγ receptors but also with a novel, so far unidentified binding site present in αß receptors. Compounds with a high affinity for the benzodiazepine binding site stimulated GABA-induced currents stronger at αßγ than at αß receptors and preferred α3ß3γ2 receptors. Compounds showing equal or smaller effects at αßγ compared to αß receptors differentially interacted with various αß or αßγ receptor subtypes. Surprisingly, five of these compounds interacting with αß receptors showed a strong stimulation at α6ß3γ2 receptors. The absence of any direct effects at GABA(A) receptors, as well as their potential selectivity for receptor subtypes not being addressed by benzodiazepines, make this compound class to a starting point for the development of drugs with a possible clinical importance.

Transition-metal-free tunable chemoselective N functionalization of indoles with ynamides.

Two unprecedented N functionalizations of indoles with ynamides are described. By varying the electron-withdrawing group on the ynamide nitrogen atom, either Z-indolo-etheneamides or indolo-amidines can be selectively obtained under the same metal-free reaction conditions. The scope and synthetic potential of these reactions, as well as some mechanistic insights provided by DFT calculations, are reported.