Design, Synthesis, and Biological Evaluation of a Novel Series of Teriflunomide Derivatives as Potent Human Dihydroorotate Dehydrogenase Inhibitors for Malignancy Treatment.

Human dihydroorotate dehydrogenase (hDHODH), as the fourth and rate-limiting enzyme of the de novo pyrimidine synthesis pathway, is regarded as an attractive target for malignancy therapy. In the present study, a novel series of teriflunomide derivatives were designed, synthesized, and evaluated as hDHODH inhibitors. 13t was the optimal compound with promising enzymatic activity (IC50 = 16.0 nM), potent antiproliferative activity against human lymphoma Raji cells (IC50 = 7.7 nM), and excellent aqueous solubility (20.1 mg/mL). Mechanistically, 13t directly inhibited hDHODH and induced cell cycle S-phase arrest in Raji cells. The acute toxicity assay indicated a favorable safety profile of 13t. Notably, 13t displayed significant tumor growth inhibition activity with a tumor growth inhibition (TGI) rate of 81.4% at 30 mg/kg in a Raji xenograft model. Together, 13t is a promising inhibitor of hDHODH and a preclinical candidate for antitumor therapy, especially for lymphoma.

Carbon-13 synthesis and NMR spectroscopic geometric isomer evaluation to support the filing of teriflunomide.

The two isotopomers of teriflunomide were synthesized starting from isotopically stable-labeled stocks of [13 C]potassium cyanide and [1-13 C]ethyl bromoacetate. The two 13 C-labeled compounds 1a, b were applied in several NMR studies to study the E/Z ratio in different matrices. In a solution, such as dimethyl sulfoxide (DMSO), a dynamic equilibrium between E/Z-isomers (ratio of 8:92) was determined by initial 13 C-carbon NMR experiments. To get insights into the E/Z ratio of teriflunomide under in vivo conditions, advanced heteronuclear NMR (heteronuclear Overhauser effect spectroscopy [HOESY]) in D2 O and mixtures of D2 O/plasma were performed. Whereas NMR experiments in mixtures of water and plasma failed owing to extreme line broadening, NMR spectra in water at pH 7.4 showed only the Z-isomer.

Design, microwave synthesis, and molecular docking studies of catalpol crotonates as potential neuroprotective agent of diabetic encephalopathy.

Catalpol has gained increasing attention for its potential contributions in controlling glycolipid metabolism and diabetic complications, which makes used as a very promising scaffold for seeking new anti-diabetic drug candidates. Acylation derivatives of catalpol crotonate (CCs) were designed as drug ligands of glutathione peroxidase (GSH-Px) based on molecular docking (MD) using Surfex-Docking method. Catalpol hexacrotonate (CC-6) was synthesized using microwave assisted method and characterized by FT-IR, NMR, HPLC and HRMS. The MD results indicate that with the increasing of esterification degree of hydroxyl, the C log P of CCs increased significantly, and the calculated total scores (Total_score) of CCs are all higher than that of catalpol. It shows that CCs maybe served as potential lead compounds for neuroprotective agents. It was found that the maximum Total_score of isomers in one group CCs is often not that the molecule with minimum energy. MD calculations show that there are five hydrogen bonds formed between CC-6 and the surrounding amino acid residues. Molecular dynamics simulation results show that the binding of CC-6 with GSH-Px is stable. CC-6 was screened for SH-SY5Y cells viability by MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) assay, the result indicates CC-6 can effectively reverse SZT induced cells apoptosis with dose-dependent manner, which can indirectly show that CC-6 is a potential neuroprotective agent.

γ-Cyclodextrin-metal organic frameworks as efficient microcontainers for encapsulation of leflunomide and acceleration of its transformation into teriflunomide.

γ-Cyclodextrin-based metal-organic framework (γCD-MOF) crystals were successfully synthesized using a vapor diffusion method. An applicability of γCD-MOF for encapsulation of immunosuppressive disease-modifying antirheumatic drug leflunomide (LEF) was examined. Loading of LEF in γCD-MOF was performed by impregnation and co-crystallization. The empty and loaded γCD-MOFs were characterized using X-ray powder diffraction, N2 adsorption/desorption, thermogravimetric analysis, 1H NMR and FTIR spectroscopy. It was shown that in the presence of γCD-MOF leflunomide is transformed into its pharmacologically active form - teriflunomide that can be also applied alone in the treatment of multiple sclerosis. It was demonstrated that teriflunomide released from γCD-MOF has improved pharmacologically relevant properties such as solubility, dissolution rate and membrane permeability. It can be proposed that γCD-MOF can be considered as novel strategy for delivery of leflunomide.

Chemical genetic inhibition of DEAD-box proteins using covalent complementarity.

DEAD-box proteins are an essential class of enzymes involved in all stages of RNA metabolism. The study of DEAD-box proteins is challenging in a native setting since they are structurally similar, often essential and display dosage sensitivity. Pharmacological inhibition would be an ideal tool to probe the function of these enzymes. In this work, we describe a chemical genetic strategy for the specific inactivation of individual DEAD-box proteins with small molecule inhibitors using covalent complementarity. We identify a residue of low conservation within the P-loop of the nucleotide-binding site of DEAD-box proteins and show that it can be mutated to cysteine without a substantial loss of enzyme function to generate electrophile-sensitive mutants. We then present a series of small molecules that rapidly and specifically bind and inhibit electrophile-sensitive DEAD-box proteins with high selectivity over the wild-type enzyme. Thus, this approach can be used to systematically generate small molecule-sensitive alleles of DEAD-box proteins, allowing for pharmacological inhibition and functional characterization of members of this enzyme family.

Antibacterial Effect of (2E,2E)-4,4-Trisulfanediylbis(but-2-enoic acid) against Staphylococcus aureus.

A new highly active molecule, (2E, 2E)-4,4-trisulfanediylbis(but-2-enoic acid) (TSDB), was designed and synthesized through comparative molecular field analysis with the diallyl trisulfide structure of garlic. TSDB exerted a strong inhibitory effect against Staphylococcus aureus, with minimal inhibitory and minimal bactericidal concentrations of 16 and 128 µg/mL, respectively. TSDB destructed the integrity of the S. aureus cell membrane but weakly damaged the bacterial cell wall. TSDB also increased the conductivity and protein expression in microbial broth but minimally influenced the level of extracellular alkaline phosphatase. TSDB could be a novel food preservative.

Molecular Hybridization of Potent and Selective γ-Hydroxybutyric Acid (GHB) Ligands: Design, Synthesis, Binding Studies, and Molecular Modeling of Novel 3-Hydroxycyclopent-1-enecarboxylic Acid (HOCPCA) and trans-γ-Hydroxycrotonic Acid (T-HCA) Analogs.

γ-Hydroxybutyric acid (GHB) is a neuroactive substance with specific high-affinity binding sites. To facilitate target identification and ligand optimization, we herein report a comprehensive structure-affinity relationship study for novel ligands targeting these binding sites. A molecular hybridization strategy was used based on the conformationally restricted 3-hydroxycyclopent-1-enecarboxylic acid (HOCPCA) and the linear GHB analog trans-4-hydroxycrotonic acid (T-HCA). In general, all structural modifications performed on HOCPCA led to reduced affinity. In contrast, introduction of diaromatic substituents into the 4-position of T-HCA led to high-affinity analogs (medium nanomolar Ki) for the GHB high-affinity binding sites as the most high-affinity analogs reported to date. The SAR data formed the basis for a three-dimensional pharmacophore model for GHB ligands, which identified molecular features important for high-affinity binding, with high predictive validity. These findings will be valuable in the further processes of both target characterization and ligand identification for the high-affinity GHB binding sites.

Efficient synthesis of the GABAA receptor agonist trans-4-aminocrotonic acid (TACA).

Investigations into the pharmacology of different types of cys-loop GABA receptor have relied for years on the chemical modification of GABA-like compounds. The GABA metabolite GABOB is an attractive molecule to modify due to its convenient chemical structure. In the process of developing new GABA-mimic compounds from GABOB as a starting compound three small molecule GABA derivatives were synthesized using a variety of chemical transformations. Amongst these, a new and reliable method to synthesize TACA (trans-4-aminocrotonic acid) is reported.

Superelectrophilic Activation of Crotonic/Methacrylic Acids: Direct Access to Thiochroman-4-ones from Benzenethiols by Microwave-Assisted One-Pot Alkylation/Cyclic Acylation.

An efficient microwave-assisted protocol for the synthesis of 2-/3-methylthiochroman-4-ones by superacid-catalyzed alkylation followed by cyclic acylation (cyclization via intramolecular acylation) is described. Using easily accessible benzenethiols and crotonic acid/methacrylic acid with triflic acid (as catalyst of choice for needed optimal acidity), the reaction was tuned toward the formation of the cyclized products in good selectivity and yield. A mechanism involving the formation of carbenium-carboxonium superelectrophilic species is suggested.

Synthesis and Biological Evaluation of (S)-Amino-2-methyl-4-[(76)Br]bromo-3-(E)-butenoic Acid (BrVAIB) for Brain Tumor Imaging.

The novel compound, (S)-amino-2-methyl-4-[(76)Br]bromo-3-(E)-butenoic acid (BrVAIB, [(76)Br]5), was characterized against the known system A tracer, IVAIB ([(123)I]8). [(76)Br]5 was prepared in a 51% ± 19% radiochemical yield with high radiochemical purity (≥98%). The biological properties of [(76)Br]5 were compared with those of [(123)I]8. Results showed that [(76)Br]5 undergoes mixed amino acid transport by system A and system L transport, while [(123)I]8 had less uptake by system L. [(76)Br]5 demonstrated higher uptake than [(123)I]8 in DBT tumors 1 h after injection (3.7 ± 0.4% ID/g vs 1.5 ± 0.3% ID/g) and also showed higher uptake vs [(123)I]8 in normal brain. Small animal PET studies with [(76)Br]5 demonstrated good tumor visualization of intracranial DBTs up to 24 h with clearance from normal tissues. These results indicate that [(76)Br]5 is a promising PET tracer for brain tumor imaging and lead compound for a mixed system A and system L transport substrate.

Microwave-assisted synthesis, molecular docking, and cholinesterase inhibitory activities of new ethanediamide and 2-butenediamide analogues.

A novel series of meta-substituted ethanediamide and 2-butenediamide derivatives were synthesized and tested for their ability to inhibit electric eel acetylcholinesterase (AChE) and equine serum butyrylcholinesterase (BuChE). The synthesized compounds were evaluated against ChE enzymes using the colorimetric method described by Ellman et al. (Biochem. Pharmacol., 7, 1961). It was revealed that some synthesized compounds exhibited high anticholinesterase activity, among which compounds 1f and 2f were the most active inhibitors against BuChE (IC50 value=1.47 µM) and AChE (IC50 value=2.09 µM), respectively. Docking simulations revealed that the inhibitors 1f and 2f are capable of simultaneously binding the peripheral anionic site as well as the catalytic anionic site of both ChE enzymes. These derivatives are considered interesting candidates for Alzheimer's disease treatment.

A unified strategy for the synthesis of the C1-C14 fragment of marinolic acids, mupirocins, pseudomonic acids and thiomarinols: total synthesis of pseudomonic acid methyl monate C.

A flexible stereoselective approach to the common C1-C14 skeleton present in natural products of the pseudomonic acid family is described. The strategy has been extended and the total synthesis of pseudomonic acid methyl monate C was achieved. The key synthetic reactions utilized include Achmatowicz rearrangement, Johnson-Claisen rearrangement, Julia-Kocienski olefination, and Horner-Wadsworth-Emmons olefination reaction.

Synthesis of novel therapeutic agents for the treatment of multiple sclerosis: a brief overview.

Multiple sclerosis (MS) often results in chronic inflammatory and autoimmune disorders, and recent developments in understanding the disease pathogenesis has lead to newer therapeutic options for the treatment of the disease. The development of small molecule drugs with improved efficacy, better tolerability, and oral administration has received a new impetus with the discovery of newer classes of drugs. In this review, we have summarized the hitherto known synthetic strategies of fingolimod, laquinimod, cladribine, and teriflunomide reported in the literature which are the key small molecules and the first oral drug candidates for MS in various stages of clinical development or have been launched in the market.

Ligand-free Suzuki coupling of arylboronic acids with methyl (E)-4-bromobut-2-enoate: synthesis of unconventional cores of HIV-1 protease inhibitors.

An effective ligand-free Suzuki coupling protocol to unite methyl (E)-4-bromobut-2-enoate with several arylboronic acids has been accomplished. Thus, a number of variously functionalized methyl 4-arylcrotonates have been achieved in high to excellent yields under mild conditions. This method enables the preparation of diverse aryl-substituted cores of HIV-1 protease inhibitors.

Organocatalytic asymmetric sulfa-Michael addition of thiols to 4,4,4-trifluorocrotonates.

The first asymmetric sulfa-Michael addition of thiols to 4,4,4-trifluorocrotonates for the construction of a stereogenic center bearing a unique trifluoromethyl group and a sulfur atom has been achieved in high yields and excellent enantioselectivities with a 1 mol % bifunctional organocatalyst. Subsequent transformation led to the expedient preparation of enantioenriched thiochroman-4-one and the key intermediate of the potent inhibitor of MMP-3, (R)-γ-trifluoromethyl γ-sulfone hydroxamate.

Antiproliferative activity of aroylacrylic acids. Structure-activity study based on molecular interaction fields.

Antiproliferative activity of 27 phenyl-substituted 4-aryl-4-oxo-2-butenoic acids (aroylacrylic acids) toward Human cervix carcinoma (HeLa), Human chronic myelogenous leukemia (K562) and Human colon tumor (LS174) cell lines in vitro are reported. Compounds are active toward all examined cell lines. The most active compounds bear two or three branched alkyl or cycloalkyl substituents on phenyl moiety having potencies in low micromolar ranges. One of most potent derivatives arrests the cell cycle at S phase in HeLa cells. The 3D QSAR study, using molecular interaction fields (MIF) and derived alignment independent descriptors (GRIND-2), rationalize the structural characteristics correlated with potency of compounds. Covalent chemistry, most possibly involved in the mode of action of reported compounds, was quantitatively accounted using frontier molecular orbitals. Pharmacophoric pattern of most potent compounds are used as a template for virtual screening, to find similar ones in database of compounds screened against DTP-NCI 60 tumor cell lines. Potency of obtained hits is well predicted.

Enantioselective synthesis and stereochemical revision of communiols A-C, antibacterial 2,4-disubstituted tetrahydrofurans from the coprophilous fungus Podospora communis.

The enantioselective synthesis of the originally proposed structure of communiol C, an antibacterial 2,4-disubstituted tetrahydrofuran natural product from the coprophilous fungus Podospora communis, and its epimer via the Sharpless asymmetric dihydroxylation as the source of chirality led us to propose that the genuine stereochemistry of communiol C should be 3R, 5R, and 6S. The synthesis of the (3R,5R,6S)-isomer of communiol C and its good accordance with natural communiol C in every respect enabled us to confirm the newly proposed (3R,5R,6S)-stereochemistry for communiol C. The stereochemistries of structurally-related natural products (communiols A and B) of the same microbial origin were also revised through their total synthesis.

Molecular basis of the antitumor activities of 2-crotonyloxymethyl-2-cycloalkenones.

The antitumor activity of 2-crotonyloxymethyl-2-cyclohexenone (COMC-6) is not the result of the GSH conjugate (GSMC-6) formed inside tumor cells, as the diethyl ester prodrug form of GSMC-6 displays little antitumor activity with B16 melanotic melanoma in vitro (IC(50) > 460 microM) versus COMC-6 (IC(50) 0.041 microM) and its five- and seven-membered ring homologues. Antitumor activity probably results from a reactive intermediate that forms during conjugation of the COMCs with intracellular GSH.

Syntheses of (Z)-and (E)-4-amino-2-(trifluoromethyl)-2-butenoic acid and their inactivation of gamma-aminobutyric acid aminotransferase.

(Z)- and (E)-4-amino-2-(trifluoromethyl)-2-butenoic acid (4 and 5, respectively) were synthesized and investigated as potential mechanism-based inactivators of gamma-aminobutyric acid aminotransferase (GABA-AT) in a continuing effort to map the active site of this enzyme. The core alpha-trifluoromethyl-alpha,beta-unsaturated ester moiety was prepared via a Reformatsky/reductive elimination coupling of the key intermediates tert-butyl 2,2-dichloro-3,3,3-trifluoropropionate and N,N-bis(tert-butoxy-carbonyl)glycinal. Both 4 and 5 inhibited GABA-AT in a time-dependent manner, but displayed non-pseudo-first-order inactivation kinetics; initially, the inactivation rate increased with time. Further investigation demonstrated that the actual inactivator is generated enzymatically from 4 or 5. This inactivating species is released from the active site prior to inactivation, and as a result, 4 and 5 cannot be defined as mechanism-based inactivators. Furthermore, 4 and 5 are alternate substrates for GABA-AT, transaminated by the enzyme with Km values of 0.74 and 20.5 mM, respectively. Transamination occurs approximately 276 and 305 times per inactivation event for 4 and 5, respectively. The enzyme also catalyzes the elimination of the fluoride ion from 4 and 5. A mechanism to account for these observations is proposed.

4-bromotiglic acid, a novel inhibitor of thiolases and a tool for assessing the cooperation between the membrane-bound and soluble beta-oxidation systems of rat liver mitochondria.

An inhibitor of long-chain 3-ketoacyl-CoA thiolase has been developed as a tool for probing the cooperation between the two fatty acid beta-oxidation systems located in the inner mitochondrial membrane and in the mitochondrial matrix, respectively. 4-Bromotiglic acid was synthesized and found to inhibit palmitoylcarnitine-supported respiration of rat liver mitochondria in concentration-dependent and time-dependent fashions. Complete inhibition of respiration was achieved after incubating coupled mitochondria with 10 microM 4-bromotiglic acid for 2 min. Uncoupled mitochondria were resistant to the toxic effect of the inhibitor. Inhibition of octanoate-supported or octanoylcarnitine-supported respiration was partially reversed when the inhibitor was removed from the incubation medium. Such reversal was not observed with either palmitoylcarnitine or 2-methyldecanoic acid as the respiratory substrate. The severity of the irreversible inhibition declined with decreasing chain length of the acylcarnitine substrate. Of all beta-oxidation enzymes, only thiolases were inactivated by the inhibitor. Under conditions at which acetoacetyl-CoA thiolase and long-chain thiolase were completely inactivated, 3-ketoacyl-CoA thiolase retained some activity. It is concluded that the degradation of palmitic acid and longer-chain fatty acids is initiated by the beta-oxidation system of the inner membrane, whereas fatty acids shorter than palmitic acid can be oxidized to a certain degree by the matrix system alone. The effectiveness of the matrix system increases with decreasing chain length of the substrate.