Virtual Fragment Screening Identification of a Quinoline‐5,8‐dicarboxylic Acid Derivative as a Selective JMJD3 Inhibitor

The quinoline‐5,8 dicarboxylic acid scaffold has been identified by a fragment‐based approach as new potential lead compound for the development of JMJD3 inhibitors. Among them, 3‐(2,4‐dimethoxypyrimidin‐5‐yl)quinoline‐5,8‐dicarboxylic acid (compound 3 ) shows low micromolar inhibitory activity against Jumonji domain‐containing protein 3 (JMJD3). The experimental evaluation of inhibitory activity against seven related isoforms of JMJD3 highlighted an unprecedented selectivity toward the biological target of interest.     

CycloSal‐phosphate Pronucleotides of Cytostatic 6‐(Het)aryl‐7‐deazapurine Ribonucleosides: Synthesis,Cytostatic Activity,and Inhibition of Adenosine Kinases

A series of cycloSal‐phosphate prodrugs of a recently described new class of nucleoside cytostatics (6‐hetaryl‐7‐deazapurine ribonucleosides) was prepared. The corresponding 2′,3′‐isopropylidene 6‐chloro‐7‐deazapurine nucleosides were converted into 5‐O′‐cycloSal‐phosphates. These underwent a series of Stille or Suzuki cross‐couplings with diverse (het)arylstannanes or ‐boronic acids to yield the protected 6‐(het)aryl‐7‐deazapurine pronucleotides that were subsequently deprotected to give 12 derivatives of free pronucleotides. The in vitro cytostatic effect of the pronucleotides was compared with parent nucleoside analogues. In most cases, the activity of the pronucleotide was similar to or somewhat lower than that of the corresponding parent nucleosides, with the exception of 7‐fluoro pronucleotides 13 a , 13 b , and 13 d , which had exhibited GIC₅₀ values that were improved by one order of magnitude (to the low nanomolar range). The presence of a cycloSal‐phosphate group also influenced selectivity toward various cell lines. Several pronucleotides were found which strongly inhibit human adenosine kinase but only weakly inhibit the MTB adenosine kinase.     

Multiple Roles of the Pyrimidyl Group in the Rhodium‐Catalyzed Regioselective Synthesis and Functionalization of Indole‐3‐carboxylic Acid Esters

A regioselective synthesis of indole‐3‐carboxylic acid esters from anilines and diazo compounds has been realized by making use of the pyrimidyl group‐assisted rhodium‐catalyzed C H activation and C N bond formation. The reaction proceeds under mild conditions, exhibits good functional group tolerance and scalability. Reutilization of the pyrimidyl directing group in the resulting products provided an efficient strategy for further C‐7 functionalization of indoles. Moreover, the pyrimidyl moiety could be readily removed as a leaving group to offer various free N H indoles.

     

Synthesis and Evaluation of Water‐Soluble Prodrugs of Ursodeoxycholic Acid (UDCA), an Anti‐apoptotic Bile Acid

Ursodeoxycholic acid (UDCA) is a bile acid with demonstrated anti‐apoptotic activity in both in vitro and in vivo models. However, its utility is hampered by limited aqueous solubility. As such, water‐soluble prodrugs of UDCA could have an advantage over the parent bile acid in indications where intravenous administration might be preferable, such as decreasing damage from stroke or acute kidney injury. Five phosphate prodrugs were synthesized, including one incorporating a novel phosphoryloxymethyl carboxylate (POMC) moiety. These prodrugs were highly water‐soluble, but showed significant differences in chemical stability, with oxymethylphosphate prodrugs being the most unstable. In a series of NMR experiments, the POMC prodrug was bioactivated to UDCA by alkaline phosphatase (AP) faster than a prodrug containing a phosphate directly attached to the alcohol at the 3‐position of UDCA. Both of these prodrugs showed significant anti‐apoptotic activity in a series of in vitro assays, although the POMC prodrug required the addition of AP for activity, while the other compound was active without exogenous AP.     

Synthesis of α‐Branched Acyclic Nucleoside Phosphonates as Potential Inhibitors of Bacterial Adenylate Cyclases

Inhibition of Bordetella pertussis adenylate cyclase toxin (ACT) and Bacillus anthracis edema factor (EF), key virulence factors with adenylate cyclase activity, represents a potential method for treating or preventing toxemia related to whooping cough and anthrax, respectively. Novel α‐branched acyclic nucleoside phosphonates (ANPs) having a hemiaminal ether moiety were synthesized as potential inhibitors of bacterial adenylate cyclases. ANPs prepared as bisamidates were not cytotoxic, but did not exhibit any profound activity (IC₅₀>10 μm ) toward ACT in J774A.1 macrophages. The apparent lack of activity of the bisamidates is speculated to be due to the inefficient formation of the biologically active species (ANPpp) in the cells. Conversely, two 5‐haloanthraniloyl‐substituted ANPs in the form of diphosphates were shown to be potent ACT and EF inhibitors with IC₅₀ values ranging from 55 to 362 nm .     

3‐Amidocoumarins as Potential Multifunctional Agents against Neurodegenerative Diseases

Monoamine oxidase (MAO) generates reactive oxygen species (ROS), which cause neuronal cell death, causing neurodegeneration. Agents that are able to concurrently inhibit MAO and scavenge free radicals represent promising multifunctional neuroprotective agents that could be used to delay or slow the progression of neurodegenerative diseases. In this work, variously substituted 3‐amidocoumarins are described that exert neuroprotection in vitro against hydrogen peroxide in rat cortical neurons, as well as antioxidant activity in a 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH?) radical scavenging assay. Selective and reversible inhibitors of the MAO‐B isoform were identified. Interestingly, in the case of the 3‐benzamidocoumarins, substitution at position 4 with a hydroxy group abolishes MAO‐B activity, but the compounds remain active in the neuroprotection model. Further evaluation of 3‐heteroarylamide derivatives indicates that it is the nature of the heterocycle that determines the neuroprotective effects. Evaluation in a parallel artificial membrane permeability assay (PAMPA) highlighted the need to further improve the blood–brain barrier permeability of this compound class. However, the compounds described herein adhere to Lipinski′s rule of five, suggesting that this novel scaffold has desirable properties for the development of potential drug candidates.     

Molecular Design of an Environmentally Sensitive Fluorescent Nucleoside, 3‐Deaza‐2′‐Deoxyadenosine Derivative: Distinguishing Thymine by Probing the DNA Minor Groove

An environmentally sensitive fluorescent nucleoside containing a 3‐deazaadenine skeleton has been developed, and its photophysical properties were investigated. Newly developed C3‐naphthylethynylated 3‐deaza‐2′‐deoxyadenosine (^3nzA, 1 ) exhibited dual fluorescence emission from an intramolecular charge‐transfer state and a locally excited state, depending upon molecular coplanarity. DNA probes containing 1 clearly discriminated a perfectly matched thymine base on the complementary strand by a distinct change in emission wavelength.     

7‐Azidomethoxy‐Coumarins as Profluorophores for Templated Nucleic Acid Detection

Templated nucleic acid detection is an emerging bioanalytical method that makes use of the target DNA or RNA strand to initiate a fluorogenic reaction. The Staudinger reduction holds particular promise for templated sensing of nucleic acids because the involved functional groups are highly chemoselective. Here, the azidomethoxy group, which can be removed under Staudinger conditions, is used to cage 7‐hydroxycoumarin fluorophores. Reduction by phosphines and subsequent loss of the azidomethoxy substituent induce a significant bathochromic shift of the major absorbance band in the near UV region. When excited at the appropriate wavelength, this change in the absorbance spectrum translates into a substantial fluorescence turn‐on signal. The described profluorophores are readily conjugated to amino‐modified DNAs and are rapidly uncaged by a triphenylphosphine–DNA probe under the control of a DNA template. In addition, turnover of the probes on the target strand occurs and yields substantial signal amplification.     

Structure‐Based Design,Synthesis, and Evaluation of 2′‐(2‐Hydroxyethyl)‐2′‐deoxyadenosine and the 5′‐Diphosphate Derivative as Ribonucleotide Reductase Inhibitors

Analysis of the recently solved X‐ray crystal structures of Saccharomyces cerevisiae ribonucleotide reductase I (ScRnr1) in complex with effectors and substrates led to the discovery of a conserved water molecule located at the active site that interacted with the 2′‐hydroxy group of the nucleoside ribose. In this study 2′‐(2‐hydroxyethyl)‐2′‐deoxyadenosine 1 and the 5′‐diphosphate derivative 2 were designed and synthesized to see if the conserved water molecule could be displaced by a hydroxymethylene group, to generate novel RNR inhibitors as potential antitumor agents. Herein we report the synthesis of analogues 1 and 2 , and the co‐crystal structure of adenosine diphosphate analogue 2 bound to ScRnr1, which shows the conserved water molecule is displaced as hypothesized.     

Multicomponent Reactions of Phosphines,Enynedioates and Cinnamaldimines Give γ‐Lactams with a 1,3,5‐Hexatriene Moiety for Facile 6π Electrocyclization: Access to Oxindoles,Isatins and Isoxazolinones

Multicomponent reactions of phosphines, enynedioates and cinnamaldimines generated 3‐phosphorus ylide γ‐lactams having a 1,3,5‐hexatriene moiety with low activation energy barrier for 6π electrocyclization, through initial formation of 1,3‐dipoles from the α(δ′)‐Michael addition of phosphines to enynedioates. The reactive 1,3‐dipoles underwent addition to cinnamaldimines, lactamization, 6π electrocyclization and oxidation to give 3‐phosphorus ylide oxindoles as platform molecules toward isatins and isoxazolinones. The key step, 6π electrocyclization, was further examined by a kinetic and a computational study.

     

Nucleation Effect of Layered Metal Phosphonate on Crystallization of Bacterial Poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyhexanoate)]

The nucleating effect of zinc phenylphosphonate (PPZn) was investigated on the as‐bacterially synthesized poly(3‐hydroxybutyrate) [P(3HB)] and poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyhexanoate)]s [P(3HB‐co‐3HHx)s] in order to improve their crystallization rate. PPZn is found an efficient nucleating agent on the crystallization of P(3HB) and P(3HB‐co‐3HHx) with low 3HHx unit content. The nucleation mechanism is proposed to be epitaxial nucleation. Both the comonomer‐unit composition and its distribution of P(3HB‐co‐3HHx)s were found exhibiting significant effect on the nucleating effect of PPZn. It is found that PPZn is more efficient on nucleating the crystallization of P(3HB‐co‐3HHx) with a broader comonomer‐unit compositional distribution than that with a narrower distribution.

     

Development of Structurally Diverse N‐Heterocyclic Carbene Ligands via Palladium‐Copper‐Catalyzed Decarboxylative Arylation of Pyrazolo[1,5‐a]pyridine‐3‐carboxylic Acid

A series of fused non‐classical normal N‐heterocyclic carbenes, Pyrpy‐NHC precursors derived from pyrazolo[1,5‐a]pyridines, has been prepared using palladium‐copper‐catalyzed decarboxylative arylation of pyrazolo[1,5‐a]pyridine‐3‐carboxylic acid. Air‐stable palladium and rhodium complexes of these ligands have been synthesized via mild transmetallation of Ag‐Pyrpy‐NHC. The structural properties of Rh(Pyrpy‐NHC)(COD)Cl complexes were determined via X‐ray analysis. The measurement of the CO stretching frequencies of dicarbonyl Rh‐Pyrpy‐NHC complexes revealed that the electron donating strength of Pyrpy‐NHC could be tuned by varying the substituents of the aryl group. A catalytic study of the Pd‐Pyrpy‐NHC complexes revealed promising activity in the Suzuki–Miyaura reaction under ambient atmospheric conditions.

     

Discovery of α‐Substituted Imidazole‐4‐acetic Acid Analogues as a Novel Class of ρ1 γ‐Aminobutyric Acid Type A Receptor Antagonists with Effect on Retinal Vascular Tone

The ρ‐containing γ‐aminobutyric acid type A receptors (GABA_ARs) play an important role in controlling visual signaling. Therefore, ligands that selectively target these GABA_ARs are of interest. In this study, we demonstrate that the partial GABA_AR agonist imidazole‐4‐acetic acid (IAA) is able to penetrate the blood–brain barrier in vivo; we prepared a series of α‐ and N‐alkylated, as well as bicyclic analogues of IAA to explore the structure–activity relationship of this scaffold focusing on the acetic acid side chain of IAA. The compounds were prepared via IAA from l ‐histidine by an efficient minimal‐step synthesis, and their pharmacological properties were characterized at native rat GABA_ARs in a [³H]muscimol binding assay and at recombinant human α₁β₂γ_2S and ρ₁ GABA_ARs using the FLIPR? membrane potential assay. The (+)‐α‐methyl‐ and α‐cyclopropyl‐substituted IAA analogues ((+)‐ 6 a and 6 c , respectively) were identified as fairly potent antagonists of the ρ₁ GABA_AR that also displayed significant selectivity for this receptor over the α₁β₂γ_2S GABA_AR. Both 6 a and 6 c were shown to inhibit GABA‐induced relaxation of retinal arterioles from porcine eyes.     

(R)‐α‐Lipoyl‐Glycyl‐L‐Prolyl‐L‐Glutamyl Dimethyl Ester Codrug as a Multifunctional Agent with Potential Neuroprotective Activities

The (R)‐α‐lipoyl‐glycyl‐L ‐prolyl‐L ‐glutamyl dimethyl ester codrug (LA‐GPE, 1 ) was synthesized as a new multifunctional drug candidate with antioxidant and neuroprotective properties for the treatment of neurodegenerative diseases. Physicochemical properties, chemical and enzymatic stabilities were evaluated, along with the capacity of LA‐GPE to penetrate the blood–brain barrier (BBB) according to an in vitro parallel artificial membrane permeability assay for the BBB. We also investigated the potential effectiveness of LA‐GPE against the cytotoxicity induced by 6‐hydroxydopamine (6‐OHDA) and H₂O₂ on the human neuroblastoma cell line SH‐SY5Y by using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) reduction assay. Our results show that codrug 1 is stable at both pH 1.3 and 7.4, exhibits good lipophilicity (log P=1.51) and a pH‐dependent permeability profile. Furthermore, LA‐GPE was demonstrated to be significantly neuroprotective and to act as an antioxidant against H₂O₂‐ and 6‐OHDA‐induced neurotoxicity in SH‐SY5Y cells.     

Cell‐Permeable β‐Peptide Inhibitors of p53/hDM2 Complexation

Look at what the cat(ionic motif) dragged in! We report a general strategy to increase the cell permeability of β³‐peptides. Introduction of a minimal cationic motif within the folded structure of a high‐affinity β³‐peptide ligand for hDM2 led to molecules with high 3₁₄‐helical structure, high hDM2 affinity and sufficient cell permeability to upregulate p53‐dependent genes in live mammalian cells. Minimally cationic β³‐peptides represent the critical first step towards a class of protease‐resistant peptidomimetics that might modulate intracellular biological pathways.

     

Bisamidate Prodrugs of 2‐Substituted 9‐[2‐(Phosphonomethoxy)ethyl]adenine (PMEA,adefovir) as Selective Inhibitors of Adenylate Cyclase Toxin from Bordetella pertussis

Novel small‐molecule agents to treat Bordetella pertussis infections are highly desirable, as pertussis (whooping cough) remains a serious health threat worldwide. In this study, a series of 2‐substituted derivatives of 9‐[2‐(phosphonomethoxy)ethyl]adenine (PMEA, adefovir), in their isopropyl ester bis(L ‐phenylalanine) prodrug form, were designed and synthesized as potent inhibitors of adenylate cyclase toxin (ACT) isolated from B. pertussis. The series consists of PMEA analogues bearing either a linear or branched aliphatic chain or a heteroatom at the C2 position of the purine moiety. Compounds with a small C2 substituent showed high potency against ACT without cytotoxic effects as well as good selectivity over human adenylate cyclase isoforms AC1, AC2, and AC5. The most potent ACT inhibitor was found to be the bisamidate prodrug of the 2‐fluoro PMEA derivative (IC₅₀=0.145 μM ). Although the bisamidate prodrugs reported herein exhibit overall lower activity than the bis(pivaloyloxymethyl) prodrug (adefovir dipivoxil), their toxicity and plasma stability profiles are superior. Furthermore, the bisamidate prodrug was shown to be more stable in plasma than in macrophage homogenate, indicating that the free phosphonate can be effectively distributed to target tissues, such as the lungs. Thus, ACT inhibitors based on acyclic nucleoside phosphonates may represent a new strategy to treat whooping cough.