ω‐Imidazolyl‐ and ω‐Tetrazolylalkylcarbamates as Inhibitors of Fatty Acid Amide Hydrolase: Biological Activity and in vitro Metabolic Stability

Fatty acid amide hydrolase (FAAH) is a serine hydrolase that terminates the analgesic and anti‐inflammatory effects of endocannabinoids such as anandamide. Herein, structure–activity relationship studies on a new series of aryl N‐(ω‐imidazolyl‐ and ω‐tetrazolylalkyl)carbamate inhibitors of FAAH were investigated. As one result, a pronounced increase in inhibitory potency was observed if a phenyl residue attached to the carbamate oxygen atom was replaced by a pyridin‐3‐yl moiety. The most active compounds exhibited IC₅₀ values in the low nanomolar range. In addition, investigations on the metabolic properties of these inhibitors were performed. In rat liver homogenate and in porcine plasma, the extent of their degradation was shown to be strongly dependent on the kind of aryl residue bound to the carbamate as well as on the length and type of the alkyl spacer connecting the carbamate group with the heterocyclic system. With the aid of esterase inhibitors it was shown that in porcine plasma, carboxylesterase‐like enzymes and paraoxonase are involved in carbamate cleavage. Moreover, it was found that highly active pyridin‐3‐yl carbamates reacted with albumin, which led to covalent albumin adducts.     

Anticancer Potential of Small-Molecule Inhibitors of Fatty Acid Amide Hydrolase and Monoacylglycerol Lipase

Recently fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) inhibitors have been in the limelight due to their anticancer potential. Both FAAH and MAGL are the endocannabinoid degrading enzymes that hydrolyze several endogenous ligands, mainly anandamide (AEA) and 2-arachidonic glycerol (2-AG), which regulate various pathophysiological conditions in the body such as emotion, cognition, energy balance, pain sensation, neuroinflammation, and cancer cell proliferation. FAAH and MAGL inhibitors block the metabolism of AEA and 2-AG, increase endogenous levels of fatty acid amides, and exert various therapeutic effects including chronic pain, metabolic disorders, psychoses, nausea and vomiting, depression, and anxiety disorders. FAAH and MAGL are primarily neurotherapeutic targets, but their contribution to various types of carcinomas are significant. Inhibitors of these enzymes either alone or as multitarget agents, or with supra-additive effects show the potential effect in ovarian, breast, prostate, and colorectal cancers. Besides highlighting the role of FAAH and MAGL in cancer progression, this review provides an update on the anticancer capabilities of known and newly discovered FAAH and MAGL inhibitors and also provides further directions to develop FAAH and MAGL inhibitors as new candidates for cancer therapy.     

Inhibiting Endocannabinoid Hydrolysis as Emerging Analgesic Strategy Targeting a Spectrum of Ion Channels Implicated in Migraine Pain

Migraine is a disabling neurovascular disorder characterized by severe pain with still limited efficient treatments. Endocannabinoids, the endogenous painkillers, emerged, alternative to plant cannabis, as promising analgesics against migraine pain. In this thematic review, we discuss how inhibition of the main endocannabinoid-degrading enzymes, monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), could raise the level of endocannabinoids (endoCBs) such as 2-AG and anandamide in order to alleviate migraine pain. We describe here: (i) migraine pain signaling pathways, which could serve as specific targets for antinociception; (ii) a divergent distribution of MAGL and FAAH activities in the key regions of the PNS and CNS implicated in migraine pain signaling; (iii) a complexity of anti-nociceptive effects of endoCBs mediated by cannabinoid receptors and through a direct modulation of ion channels in nociceptive neurons; and (iv) the spectrum of emerging potent MAGL and FAAH inhibitors which efficiently increase endoCBs levels. The specific distribution and homeostasis of endoCBs in the main regions of the nociceptive system and their generation ‘on demand’, along with recent availability of MAGL and FAAH inhibitors suggest new perspectives for endoCBs-mediated analgesia in migraine pain.     

O‐(Triazolyl)methyl Carbamates as a Novel and Potent Class of Fatty Acid Amide Hydrolase (FAAH) Inhibitors

Inhibition of fatty acid amide hydrolase (FAAH) activity is under investigation as a valuable strategy for the treatment of several disorders, including pain and drug addiction. A number of potent FAAH inhibitors belonging to different chemical classes have been disclosed to date; O‐aryl carbamates are one of the most representative families. In the search for novel FAAH inhibitors, a series of O‐(1,2,3‐triazol‐4‐yl)methyl carbamate derivatives were designed and synthesized exploiting a copper‐ catalyzed [3+2] cycloaddition reaction between azides and alkynes (click chemistry). Exploration of the structure–activity relationships within this new class of compounds identified potent inhibitors of both rat and human FAAH with IC₅₀ values in the single‐digit nanomolar range. In addition, these derivatives showed improved stability in rat plasma and kinetic solubility in buffer with respect to the lead compound. Based on the results of the study, the novel analogues identified can be considered to be promising starting point for the development of new FAAH inhibitors with improved drug‐like properties.     

A new concept for glycosyltransferase inhibitors: nonionic mimics of the nucleotide donor of the human blood group B galactosyltransferase

Glycosyltransferases play an important role in the formation of oligosaccharides and glycoconjugates. To find suitable and selective inhibitors for this class of enzymes is still challenging. Here, we describe a novel concept that allows the design of inhibitors based on the structure of the donor substrate binding pocket. As a first step we describe the design, synthesis and analysis of inhibitors of the human blood group B galactosyltransferase (GTB). This enzyme served as a model system to study the concept, which can be used for easy access of glycosyltransferase inhibitors in general. In silico docking of bicyclic heteroaromatic ligands to GTB and experimental verification of binding affinities by saturation transfer difference NMR (STD NMR) spectroscopy gave 9-N-pentityl uric acid derivatives as non-ionic mimics of UDP. Two derivatives were synthesized and showed inhibitory activity for GTB as determined by competitive STD NMR experiments and by a radiolabeled enzyme assay.     

Synthesis,Structure–Activity,and Structure–Stability Relationships of 2‐Substituted‐N‐(4‐oxo‐3‐oxetanyl) N‐Acylethanolamine Acid Amidase (NAAA) Inhibitors

N‐Acylethanolamine acid amidase (NAAA) is a cysteine amidase that preferentially hydrolyzes saturated or monounsaturated fatty acid ethanolamides (FAEs), such as palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), which are endogenous agonists of nuclear peroxisome proliferator‐activated receptor‐α (PPAR‐α). Compounds that feature an α‐amino‐β‐lactone ring have been identified as potent and selective NAAA inhibitors and have been shown to exert marked anti‐inflammatory effects that are mediated through FAE‐dependent activation of PPAR‐α. We synthesized and tested a series of racemic, diastereomerically pure β‐substituted α‐amino‐β‐lactones, as either carbamate or amide derivatives, investigating the structure–activity and structure–stability relationships (SAR and SSR) following changes in β‐substituent size, relative stereochemistry at the α‐ and β‐positions, and α‐amino functionality. Substituted carbamate derivatives emerged as more active and stable than amide analogues, with the cis configuration being generally preferred for stability. Increased steric bulk at the β‐position negatively affected NAAA inhibitory potency, while improving both chemical and plasma stability.     

3‐Heterocycle‐Phenyl N‐Alkylcarbamates as FAAH Inhibitors: Design,Synthesis and 3D‐QSAR Studies

Carbamates are a well‐established class of fatty acid amide hydrolase (FAAH) inhibitors. Here we describe the synthesis of meta‐substituted phenolic N‐alkyl/aryl carbamates and their in vitro FAAH inhibitory activities. The most potent compound, 3‐(oxazol‐2yl)phenyl cyclohexylcarbamate ( 2 a ), inhibited FAAH with a sub‐nanomolar IC₅₀ value (IC₅₀=0.74 nM ). Additionally, we developed and validated three‐dimensional quantitative structure–activity relationships (QSAR) models of FAAH inhibition combining the newly disclosed carbamates with our previously published inhibitors to give a total set of 99 compounds. Prior to 3D‐QSAR modeling, the degree of correlation between FAAH inhibition and in silico reactivity was also established. Both 3D‐QSAR methods used, CoMSIA and GRID/GOLPE, produced statistically significant models with coefficient of correlation for external prediction (R²_PRED) values of 0.732 and 0.760, respectively. These models could be of high value in further FAAH inhibitor design.     

1-(3-biaryloxy-2-oxopropyl)indole-5-carboxylic acids and related compounds as dual inhibitors of human cytosolic phospholipase A2α and fatty acid amide hydrolase

Cytosolic phospholipase A2α (cPLA2α) and fatty acid amide hydrolase (FAAH) are enzymes that have emerged as attractive targets for the development of analgesic and anti-inflammatory drugs. We recently reported that 1-[3-(4-octylphenoxy)-2-oxopropyl]indole-5-carboxylic acid (5) is a dual inhibitor of cPLA2α and FAAH. Structure-activity relationship studies revealed that substituents at the indole 3- and 5-positions and replacement of the indole scaffold of this compound by other heterocycles strongly influences the inhibitory potency against cPLA2α and FAAH, respectively. Herein we report the effect of variation of the 4-octyl residue of 5 and an exchange of its carboxylic acid moiety by some bioisosteric functional groups. Several of the compounds assayed were favorably active against both enzymes, and could therefore represent agents with improved analgesic and anti-inflammatory qualities in comparison with selective cPLA2 α and FAAH inhibitors.     

Optimization of 1,2,5‐Thiadiazole Carbamates as Potent and Selective ABHD6 Inhibitors

At present, inhibitors of α/β‐hydrolase domain 6 (ABHD6) are viewed as a promising approach to treat inflammation and metabolic disorders. This article describes the development of 1,2,5‐thiadiazole carbamates as ABHD6 inhibitors. Altogether, 34 compounds were synthesized, and their inhibitory activity was tested using lysates of HEK293 cells transiently expressing human ABHD6 (hABHD6). Among the compound series, 4‐morpholino‐1,2,5‐thiadiazol‐3‐yl cyclooctyl(methyl)carbamate (JZP‐430) potently and irreversibly inhibited hABHD6 (IC₅₀=44 nM ) and showed ～230‐fold selectivity over fatty acid amide hydrolase (FAAH) and lysosomal acid lipase (LAL), the main off‐targets of related compounds. Additionally, activity‐based protein profiling indicated that JZP‐430 displays good selectivity among the serine hydrolases of the mouse brain membrane proteome. JZP‐430 has been identified as a highly selective, irreversible inhibitor of hABHD6, which may provide a novel approach in the treatment of obesity and type II diabetes.     

A Second Generation of Carbamate‐Based Fatty Acid Amide Hydrolase Inhibitors with Improved Activity in vivo

The fatty acid ethanolamides are a class of signaling lipids that include agonists at cannabinoid and α type peroxisome proliferator‐activated receptors (PPARα). In the brain, these compounds are primarily hydrolyzed by the intracellular serine enzyme fatty acid amide hydrolase (FAAH). O‐aryl carbamate FAAH inhibitors such as URB597 are being evaluated clinically for the treatment of pain and anxiety, but interactions with carboxylesterases in liver might limit their usefulness. Here we explore two strategies aimed at overcoming this limitation. Lipophilic N‐terminal substitutions, which enhance FAAH recognition, yield potent inhibitors but render such compounds susceptible to attack by broad‐spectrum hydrolases and inactive in vivo. By contrast, polar electron‐donating O‐aryl substituents, which decrease carbamate reactivity, yield compounds, such as URB694, that are highly potent FAAH inhibitors in vivo and less reactive with off‐target carboxylesterases. The results suggest that an approach balancing inhibitor reactivity with target recognition produces FAAH inhibitors that display significantly improved drug‐likeness.     

Synthesis and Evaluation of 2-Aminothiophene Derivatives as Staphylococcus aureus Efflux Pump Inhibitors

2-aminothiophene derivatives (2AT) in which the thiophene ring is fused with a cycloalkyl or a N-acylated piperidine ring by positions 5 and 6 and carrying a 3-carbethoxy group were synthesized and their bacterial growth and enzyme inhibitory effects against efflux proteins of Staphylococcus aureus leading to resistance to fluoroquinolones and erythromycin (ERY) were investigated. Compounds that most effectively decreases the minimum inhibitory concentrations (MICs) of ciprofloxacin (CIP) were assayed for their dose and time effects on the accumulation and efflux of ethidium bromide (EtBr) in the SA-1 strain. None of the compounds displayed antibacterial activity however, three derivatives carrying 2-amino, 2-aminoacetyl and 2-aminotrifluoroacetyl group enhanced the activity of CIP and ERY by 8- and 16-fold, respectively, and were able to restore the sensitivity of resistant strains, acting as typical efflux pump inhibitors (EPIs). The 2-aminoacetyl and 2-aminotrifluoroacetyl derivatives and two other piperidinyl 2-aminotrifluoroacetyl derivatives increased EtBr accumulation in a dose- and time-dependent manner, and one of them was also able to inhibit the EtBr efflux. Taken together, these results represent an important advance in the development of new EPIs, and demonstrate that 2AT represent a good scaffold for developing new antibiotic adjuvants.     

水溶性咪唑啉缓蚀剂的合成及缓蚀性能评

采用硬脂酸、壬酸、二乙烯三胺和羟乙基乙二胺为原料,合成了四种咪唑啉母体,以丙烯酸甲酯为烷基化试剂、氯乙酸钠为季胺化试剂分别合成新型的咪唑啉缓蚀剂。采用红外光谱对产物进行分析表征,考察咪唑啉缓蚀剂的溶解度及水溶液的稳定性,用静态失重法和电化学法研究了缓蚀剂与有机胺类复配后在HCl腐蚀介质中的缓蚀性能。结果表明,合成的咪唑啉季铵盐水溶性良好,复配后在HCl体系中缓蚀率达到85%以上,且是以阴极型为主的复合型缓蚀剂。     

Structure–Property Relationships of a Class of Carbamate‐Based Fatty Acid Amide Hydrolase (FAAH) Inhibitors: Chemical and Biological Stability

Cyclohexylcarbamic acid aryl esters are a class of fatty acid amide hydrolase (FAAH) inhibitors, which includes the reference compound URB597. The reactivity of their carbamate fragment is involved in pharmacological activity and may affect their pharmacokinetic and toxicological properties. We conducted in vitro stability experiments in chemical and biological environments to investigate the structure–stability relationships in this class of compounds. The results show that electrophilicity of the carbamate influences chemical stability, as suggested by the relation between the rate constant of alkaline hydrolysis (log k_pH9) and the energy of the lowest unoccupied molecular orbital (LUMO). Introduction of small electron‐donor substituents at conjugated positions of the O‐aryl moiety increased the overall hydrolytic stability of the carbamate group without affecting FAAH inhibitory potency, whereas peripheral non‐conjugated hydrophilic groups, which favor FAAH recognition, helped decrease oxidative metabolism in the liver.     

Corrosion inhibition of triethanolammonium bromide mono- and dibenzoate as cationic inhibitors in an acidic medium

A weight loss technique was used to determine the corrosion inhibition efficiency of synthesized alkyl mono-and dibenzoate triethanolammonium bromide derivatives (TEAMB, TEADB) in an acidic medium (2 N HCl) at different doses (50, 100, and 200 ppm). The results showed that monoderivatives had a higher corrosion inhibition efficiency than diderivatives. The results were correlated with several factors, including the alkyl chain length of the hydrophobic chains, interfacial tension (IT), critical micelle concentration (CMC), and adsorption free energy of these inhibitors. Increasing the geometric length of the alkyl chains in the synthesized inhibitors had an increasing effect on their corrosion inhibition efficiency, whereas decreasing the CMC and IT had an increasing effect on their tendency toward corrosion inhibition. The number of hydrophobic chains attached to the inhibitor molecules had a vital influence on their efficiency as corrosion inhibitors.     

Second-generation iminoxylitol-based pharmacological chaperones for the treatment of Gaucher disease

A series of O-alkyl iminoxylitol derivatives was synthesized and evaluated as β-glucocerebrosidase (GCase) inhibitors. This structure-activity study shows a dramatic influence of the position of the alkyl chain (α-C1, O2, O3, or O4) on human GCase inhibition. Remarkably, 1,2-shift of the alkyl chain from C1 to O2 was found to maintain high inhibitory potency toward GCase as well as chaperone activity at sub-inhibitory concentration (10?nM). Removal of the stereogenic center at the pseudo-anomeric position led to shorter and more practical synthetic sequences. 2-O-Alkyl iminoxylitol derivatives constitute a new promising class of leads for the treatment of Gaucher disease by means of pharmacological chaperone therapy.     

含1,2,3-三氮唑哌啶衍生物的合成

1,2,3-三氮唑环作为药效基团呈现出多种生物活性,以六氢吡啶和环氧氯丙烷为底物,在微波辐射条件下,合成了叠氮基哌啶,并以此为原料,CuI为催化剂,MeCN-H2O(10∶1,v/v)为混合溶剂,与端基炔烃进行1,3-偶极环加成反应,合成含1,2,3-三氮唑功能基的哌啶衍生物,收率70%,其结构经核磁共振谱表征。     

New synthetic seven-membered 1-azasugars displaying potent inhibition towards glycosidases and glucosylceramide transferase

Several members of a new family of seven-membered azasugars, which can be seen as 1-azasugar ring homologues, have been obtained by simple chemical transformations starting from a sugar-derived azidolactol. Unlike their piperidine counterparts, these molecules are chemically stable when they possess a hydroxy group at the pseudo-C-2 position. Biological assays with a range of carbohydrate-processing enzymes have revealed interesting potential for these compounds. A trihydroxymethyl-substituted azepane displayed strong competitive inhibition on almond beta-glucosidase (K(i)=2.5 microM) while a trihydroxylated carboxylic acid derivative proved to be a potent and selective L-fucosidase inhibitor (K(i)=41 nM). N-Butylation of these seven-membered 1-azasugars generated derivatives with some activity towards the Gaucher's disease-related glucosylceramide transferase (IC(50) 75 microM) that did not interact significantly with digestive glucosidases.     

Discovery of Pyridone‐Based Histone Deacetylase Inhibitors: Approaches for Metabolic Stability

Histone deacetylases (HDACs) are important enzymes in epigenetic regulation and are therapeutic targets for cancer. Most zinc‐dependent HDACs induce proliferation, dedifferentiation, and anti‐apoptotic effects in cancer cells. We designed and synthesized a new series of pyridone‐based HDAC inhibitors that have a pyridone ring in the core structure and a conjugated system with an olefin connecting the hydroxamic acid moiety. Consequently, most of the selected pyridone‐based HDAC inhibitors showed similar or higher inhibition profiles in addition to remarkable metabolic stability against hydrolysis relative to the corresponding lactam‐based HDAC inhibitors. Furthermore, the selectivity of the novel pyridine‐based compounds was evaluated across all of the HDAC isoforms. One of these compounds, (E)‐N‐hydroxy‐3‐{1‐[3‐(naphthalen‐2‐yl)propyl]‐2‐oxo‐1,2‐dihydropyridin‐3‐yl}acrylamide, exhibited the highest level of HDAC inhibition (IC₅₀=0.07 μM ), highly selective inhibition of class I HDAC1 and class II HDAC6 enzymes, metabolic stability in mouse liver microsomal studies, and effective growth inhibition of various cancer cell lines. Docking studies indicated that a long alkyl linker and bulky hydrophobic cap groups affect in vitro activities. Overall, the findings reported herein regarding pyridone‐based HDAC inhibitors can be used to guide future research efforts to develop new and effective anticancer therapeutics.     

The squalene-2,3-epoxide cyclase as a model for the development of new drugs

The 2,3-oxido squalene (SO) cyclases represent a group of enzymes which convert SO into polycyclic triterpenoids such as lanosterol, cycloartenol, cucurbitadienol and β-amyrin. Taking into account the postulated model of the enzymatic cyclization of SO, we have investigated the possibility of designing compounds that would be selective and potent inhibitors of SO cyclases. Due to the fundamental role of sterols in animal, higher plant and fungal tissues, these inhibitors might behave as very selective (ipocholesterolemic, antifungal or phytotoxic) drugs. Our first approach was the synthesis and biological evaluation of 2-aza-2,3-dihydrosqualene and its derivatives which, being protonated at physiological pH, would present some similarities to the C-2 carbon ion generated by the opening of the oxirane ring of SO. Microsomes from different sources (germinated pea cotyledons, maize seedlings, rat liver and yeasts) were utilized to determine the inhibition values (I₅₀: concentration of inhibitor producing 50% inhibition at a given substrate concentration). From the results obtained so far we conclude that 2-aza-2-dihydrosqualene and its derivatives strongly inhibited the cyclases, the site of the enzyme responsible for binding to the inhibitor is quite sensitive to the steric hindrance, and the degree of the inhibitory activity is greater in higher plants than in rat liver or fungi.     

6‐Methyluracil Derivatives as Bifunctional Acetylcholinesterase Inhibitors for the Treatment of Alzheimer's Disease

Novel 6‐methyluracil derivatives with ω‐(substituted benzylethylamino)alkyl chains at the nitrogen atoms of the pyrimidine ring were designed and synthesized. The numbers of methylene groups in the alkyl chains were varied along with the electron‐withdrawing substituents on the benzyl rings. The compounds are mixed‐type reversible inhibitors of cholinesterases, and some of them show remarkable selectivity for human acetylcholinesterase (hAChE), with inhibitory potency in the nanomolar range, more than 10 000‐fold higher than that for human butyrylcholinesterase (hBuChE). Molecular modeling studies indicate that these compounds are bifunctional AChE inhibitors, spanning the enzyme active site gorge and binding to its peripheral anionic site (PAS). In vivo experiments show that the 6‐methyluracil derivatives are able to penetrate the blood–brain barrier (BBB), inhibiting brain‐tissue AChE. The most potent AChE inhibitor, 3 d (1,3‐bis[5‐(o‐nitrobenzylethylamino)pentyl]‐6‐methyluracil), was found to improve working memory in scopolamine and transgenic APP/PS1 murine models of Alzheimer's disease, and to significantly decrease the number and area of β‐amyloid peptide plaques in the brain.