Organic carbamates in drug design and medicinal chemistry

Design of PSMA ligands with modifications at the inhibitor part: an approach to reduce the salivary gland uptake of radiolabeled PSMA inhibitors?

AIM

To investigate whether modifications of prostate-specific membrane antigen (PSMA)-targeted radiolabeled urea-based inhibitors could reduce salivary gland uptake and thus improve tumor-to-salivary gland ratios, several analogs of a high affinity PSMA ligand were synthesized and evaluated in in vitro and in vivo studies.

METHODS

Binding motifs were synthesized 'on-resin' or, when not practicable, in solution. Peptide chain elongations were performed according to optimized standard protocols via solid-phase peptide synthesis. In vitro experiments were performed using PSMA⁺ LNCaP cells. In vivo studies as well as μSPECT/CT scans were conducted with male LNCaP tumor xenograft-bearing CB17-SCID mice.

RESULTS

PSMA ligands with A) modifications within the central Zn²⁺-binding unit, B) proinhibitor motifs and C) substituents & bioisosteres of the P1'-γ-carboxylic acid were synthesized and evaluated. Modifications within the central Zn²⁺-binding unit of PSMA-10 (Glu-urea-Glu) provided three compounds. Thereof, only ^natLu-carbamate I (^natLu-3) exhibited high affinity (IC₅₀ = 7.1 ± 0.7 nM), but low tumor uptake (5.31 ± 0.94% ID/g, 1 h p.i. and 1.20 ± 0.55% ID/g, 24 h p.i.). All proinhibitor motif-based ligands (three in total) exhibited low binding affinities (> 1 μM), no notable internalization and very low tumor uptake (< 0.50% ID/g). In addition, four compounds with P1'-ɣ-carboxylate substituents were developed and evaluated. Thereof, only tetrazole derivative ^natLu-11 revealed high affinity (IC₅₀ = 16.4 ± 3.8 nM), but also this inhibitor showed low tumor uptake (3.40 ± 0.63% ID/g, 1 h p.i. and 0.68 ± 0.16% ID/g, 24 h p.i.). Salivary gland uptake in mice remained at an equally low level for all compounds (between 0.02 ± 0.00% ID/g and 0.09 ± 0.03% ID/g), wherefore apparent tumor-to-submandibular gland and tumor-to-parotid gland ratios for the modified peptides were distinctly lower (factor 8-45) than for [¹⁷⁷Lu]Lu-PSMA-10 at 24 h p.i.

CONCLUSIONS

The investigated compounds could not compete with the in vivo characteristics of the EuE-based PSMA inhibitor [¹⁷⁷Lu]Lu-PSMA-10. Although two derivatives (3 and 11) were found to exhibit high affinities towards LNCaP cells, tumor uptake at 24 h p.i. was considerably low, while uptake in salivary glands remained unaffected. Optimization of the established animal model should be envisaged to enable a clear identification of PSMA-targeting radioligands with improved tumor-to-salivary gland ratios in future studies.

A STAT3 inhibitor ameliorates CNS autoimmunity by restoring Teff:Treg balance

Reestablishing an appropriate balance between T effector cells (Teff) and Tregs is essential for correcting autoimmunity. Multiple sclerosis (MS) is an immune-mediated chronic CNS disease characterized by neuroinflammation, demyelination, and neuronal degeneration, in which the Teff:Treg balance is skewed toward pathogenic Teffs Th1 and Th17 cells. STAT3 is a key regulator of Teff:Treg balance. Using the structure-based design, we have developed a potentially novel small-molecule prodrug LLL12b that specifically inhibits STAT3 and suppresses Th17 differentiation and expansion. Moreover, LLL12b regulates the fate decision between Th17 and Tregs in an inflammatory environment, shifting Th17:Treg balance toward Tregs and favoring the resolution of inflammation. Therapeutic administration of LLL12b after disease onset significantly suppresses disease progression in adoptively transferred, chronic, and relapsing-remitting experimental autoimmune encephalomyelitis. Disease relapses were also significantly suppressed by LLL12b given during the remission phase. Additionally, LLL12b shifts Th17:Treg balance of CD4⁺ T cells from MS patients toward Tregs and increases Teff sensitivity to Treg-mediated suppression. These data suggest that selective inhibition of STAT3 by the small molecule LLL12b recalibrates the effector and regulatory arms of CD4⁺ T responses, representing a potentially clinically translatable therapeutic strategy for MS.

De novo design of new chemical entities for SARS-CoV-2 using artificial intelligence

Background: The novel coronavirus SARS-CoV-2 has severely affected the health and economy of several countries. Multiple studies are in progress to design novel therapeutics against the potential target proteins in SARS-CoV-2, including 3CL protease, an essential protein for virus replication. Materials & methods: In this study we employed deep neural network-based generative and predictive models for de novo design of small molecules capable of inhibiting the 3CL protease. The generative model was optimized using transfer learning and reinforcement learning to focus around the chemical space corresponding to the protease inhibitors. Multiple physicochemical property filters and virtual screening score were used for the final screening. Conclusion: We have identified 33 potential compounds as ideal candidates for further synthesis and testing against SARS-CoV-2.

Phosphine Carboxylate-Probing the Edge of Stability of a Carbon Dioxide Adduct with Dihydrogenphosphide

We present a new adduct of carbon dioxide with dihydrogenphosphide, that may be prepared either by direct reaction of NaPH₂ with carbon dioxide or by hydrolysis of the phosphaethynolate ion (PCO^- ). In this hydrolysis transformation, a new mechanism is proposed for the electrophilic reactivity of the phosphaethynolate ion. Protonation to form phosphine carboxylic acid (PH₂ COOH) and functionalization to form esters is shown to increase the strength of the P-C interaction, allowing for comparisons to be drawn between this species and the analogous carbamic (NH₂ COOH) and carbonic acids (H₂ CO₃ ). Functionalization of the oxygen atom is found to stabilize the phosphine carboxylate while also allowing solubility in organic solvents whereas phosphorus functionalization is shown to facilitate decarboxylation. Substituent migration occurs in some cases.

An insight into the anticancer potential of carbamates and thiocarbamates of 10-demethoxy-10-methylaminocolchicine

Colchicine shows very high antimitotic activity, therefore, it is used as a lead compound for generation of new anticancer agents. In the hope of developing novel, useful drugs with more favourable pharmacological profiles, a series of doubly modified colchicine derivatives has been designed, synthesized and characterized. These novel carbamate or thiocarbamate derivatives of 10-demethoxy-10-methylaminocolchicine have been tested for their antiproliferative activity against four human cancer cell lines. Additionally, their mode of action has been evaluated as colchicine binding site inhibitors, using molecular docking studies. Most of the tested compounds showed greater cytotoxicity (IC₅₀ in a low nanomolar range) and were characterized by a higher selectivity index than standard chemotherapeutics such as cisplatin and doxorubicin as well as unmodified colchicine. Their pharmacological use in cancer therapy could possibly be accomplished with lower dosages and result in less acute toxicity problems than in the case of colchicine. In addition, we present a QSAR model for predicting the antiproliferative activity of doubly modified derivatives for two tumour cell lines.

Evaluation of the penetration process of fluorescent collagenase nanocapsules in a 3D collagen gel

One of the major limitations of nanomedicine is the scarce penetration of nanoparticles in tumoral tissues. These constrains have been tried to be solved by different strategies, such as the employ of polyethyleneglycol (PEG) to avoid the opsonization or reducing the extracellular matrix (ECM) density. Our research group has developed some strategies to overcome these limitations such as the employ of pH-sensitive collagenase nanocapsules for the digestion of the collagen-rich extracellular matrix present in most of tumoral tissues. However, a deeper understanding of physicochemical kinetics involved in the nanocapsules degradation process is needed to understand the nanocapsule framework degradation process produced during the penetration in the tissue. For this, in this work it has been employed a double-fluorescent labelling strategy of the polymeric enzyme nanocapsule as a crucial chemical tool which allowed the analysis of nanocapsules and free collagenase during the diffusion process throughout a tumour-like collagen matrix. This extrinsic label strategy provides far greater advantages for observing biological processes. For the detection of enzyme, collagenase has been labelled with fluorescein Isothiocyanate (FITC), whereas the nanocapsule surface was labelled with rhodamine Isothiocyanate (RITC). Thus, it has been possible to monitor the hydrolysis of nanocapsules and their diffusion throughout a thick 3D Collagen gel during the time, obtaining a detailed temporal evaluation of the pH-sensitive collagenase nanocapsule behaviour. These collagenase nanocapsules displayed a high enzymatic activity in low concentrations at acidic pH, and their efficiency to penetrate into tissue models pave the way to a wide range of possible nanomedical applications, especially in cancer therapy.

Catalytic Decarboxylative C-N Formation to Generate Alkyl, Alkenyl, and Aryl Amines

Transition-metal-catalyzed sp² C-N bond formation is a reliable method for the synthesis of aryl amines. Catalytic sp³ C-N formation reactions have been reported occasionally, and methods that can realize both sp² and sp³ C-N formation are relatively unexplored. Herein, we address this challenge with a method of catalytic decarboxylative C-N formation that proceeds through a cascade carboxylic acid activation, acyl azide formation, Curtius rearrangement and nucleophilic addition reaction. The reaction uses naturally abundant organic carboxylic acids as carbon sources, readily prepared azidoformates as the nitrogen sources, and 4-dimethylaminopyridine (DMAP) and Cu(OAc)₂ as catalysts with as low as 0.1 mol % loading, providing protected alkyl, alkenyl and aryl amines in high yields with gaseous N₂ and CO₂ as the only byproducts. Examples are demonstrated of the late-stage functionalization of natural products and drug molecules, stereospecific synthesis of useful α-chiral alkyl amines, and rapid construction of different ureas and primary amines.

Cationic lipids for gene delivery: many players, one goal

Lipid-based carriers represent the most widely used alternative to viral vectors for gene expression and gene silencing purposes. This class of non-viral vectors is particularly attractive for their ease of synthesis and chemical modifications to endow them with desirable properties. Despite combinatorial approaches have led to the generation of a large number of cationic lipids displaying different supramolecular structures and improved behavior, additional effort is needed towards the development of more and more effective cationic lipids for transfection purposes. With this review, we seek to highlight the great progress made in the design of each and every constituent domain of cationic lipids, that is, the chemical structure of the headgroup, linker and hydrophobic moieties, and on the specific effect on the assembly with nucleic acids. Since the complexity of such systems is known to affect their performances, the role of formulation, stability and phase behavior on the transfection efficiency of such assemblies will be thoroughly discussed. Our objective is to provide a conceptual framework for the development of ever more performing lipid gene delivery vectors.

Synthesis, bioactivity and 3D-QSAR of azamacrolide compounds with a carbamate or urea moiety as potential fungicides and inhibitors of quorum sensing

Azamacrolides were synthesized and some azamacrolide compounds hold potential for the development of novel fungicides or inhibitors of quorum sensing.

Expanding the Treatment Landscape for Lennox-Gastaut Syndrome: Current and Future Strategies

Lennox-Gastaut syndrome (LGS), a childhood-onset severe developmental and epileptic encephalopathy (DEE), is an entity that encompasses a heterogenous group of aetiologies, with no single genetic cause. It is characterised by multiple seizure types, an abnormal EEG with generalised slow spike and wave discharges and cognitive impairment, associated with high morbidity and profound effects on the quality of life of patients and their families. Drug-refractory seizures are a hallmark and treatment is further complicated by its multiple morbidities, which evolve over the patient's lifetime. This review provides a comprehensive overview of the current and future options for the treatment of seizures associated with LGS. Six treatments are specifically indicated as adjunct therapies for the treatment of seizures associated with LGS in the US: lamotrigine, clobazam, rufinamide, topiramate, felbamate and most recently cannabidiol. These therapies have demonstrated reductions in drop seizures in 15%-68% of patients across trials, with responder rates (≥ 50% reduction in drop seizures) of 37%-78%. Valproate is still the preferred first-line treatment, generally in combination with lamotrigine or clobazam. Other treatments frequently used off-label include the broad spectrum anti-epileptic drugs (AED) levetiracetam, zonisamide and perampanel, while recent evidence from observational studies has indicated that a newer AED, the levetiracetam analogue brivaracetam, may be effective and well tolerated in LGS patients. Other treatments in clinical development include fenfluramine in late phase III, perampanel, soticlestat-OV953/TAK-953, carisbamate and ganaxolone. Non-pharmacologic interventions include the ketogenic diet, vagus nerve stimulation and surgical interventions; these are also expanding, with the potential for less invasive techniques for corpus callosotomy that have promise for reducing complications. However, despite these advancements, patients continue to experience a significant burden. Because LGS is not a single entity, tailoring of treatment is needed as opposed to a 'one size fits all' approach. Further research is needed into the underlying aetiologies and pathophysiology of LGS, together with advancements in treatments that encompass the spectrum of seizures associated with this complex syndrome.

Organic synthesis via Kolbe and related non-Kolbe electrolysis: an enabling electro-strategy

Herein, the electrolysis process, where the anodic oxidation of carboxylic acids leads to decarboxylation, has been discussed to synthesize organic molecules.

Identification of methyl (5-(6-((4-(methylsulfonyl)piperazin-1-yl)methyl)-4-morpholinopyrrolo[2,1-f][1,2,4]triazin-2-yl)-4-(trifluoromethyl)pyridin-2-yl)carbamate (CYH33) as an orally bioavailable, highly potent, PI3K alpha inhibitor for the treatment of advanced solid tumors

In various human cancers, PI3Ks pathway is ubiquitously dysregulated and thus become a promising anti-cancer target. To discover new potent and selective PI3K inhibitors as potential anticancer drugs, new pyrrolo[2,1-f][1,2,4]triazines were designed, leading to the discovery of compound 37 (CYH33), a selective PI3Kα inhibitor (IC50 = 5.9 nM, β/α, δ/α,γ/α = 101-, 13-, 38-fold). Western blot analysis confirmed that compound 37 could inhibit phosphorylation of AKT in human cancer cells to modulate the cellular PI3K/AKT/mTOR pathway. And further evaluation in vivo against SKOV-3 xenograft models demonstrated that a dose-dependent antitumor efficacy was achieved.

Sialyltransferase Inhibitors as Potential Anti-Cancer Agents

Sialic acid occupies a privileged position at the terminus of the glycan chain of many cell-surface glycoconjugates. Owing to both their structure and location, charged sialic acid residues mediate numerous critical interactions in cell–cell communication including cell recognition, invasion, migration, receptor binding, and immunological responses. Sialyltransferases (STs) are the enzymes involved in the biosynthesis of sialylated glycans and are highly upregulated, up to 40–60 %, in a range of cancers, with tumour hypersialylation strongly correlated with both tumour progression and treatment resistance. Accordingly, inhibiting sialylation is currently being explored by several research groups worldwide as a potential new cancer treatment strategy. However, to progress small molecule ST inhibitors into the clinic, issues around selectivity, synthetic accessibility, and cell permeability need to be addressed. Using computationally guided design principles, we produced a leading series of ST inhibitors by replacing the cytidine nucleoside with uridine and substituting the charged phosphodiester linker with a carbamate or triazole moiety. Biological evaluation of the newly developed inhibitors was performed using commercially available human ST enzymes, with the Ki inhibition values of the lead compounds ranging from 1 to 20 µM. Compared with earlier generations of sialylation inhibitors, our inhibitors are non-toxic in a range of cell studies, with improved synthetic accessibility.

Peptide-Drug Conjugates with Different Linkers for Cancer Therapy

Drug conjugates are chemotherapeutic or cytotoxic agents covalently linked to targeting ligands such as an antibody or a peptide via a linker. While antibody-drug conjugates (ADCs) are now clinically established for cancer therapy, peptide-drug conjugates (PDCs) are gaining recognition as a new modality for targeted drug delivery with improved efficacy and reduced side effects for cancer treatment. The linker in a drug conjugate plays a key role in the circulation time of the conjugate and release of the drug for full activity at the target site. Herein, we highlight the main linker chemistries utilized in the design of PDCs and discuss representative examples of PDCs with different linker chemistries with the related outcome in cell and animal studies.

Carbamate group as structural motif in drugs: a review of carbamate derivatives used as therapeutic agents

Due to their very good chemical and proteolytic stability, ability to penetrate cell membranes, and resemblance to a peptide bond, carbamate derivatives have received much attention in recent years and got an important role in modern drug discovery and medicinal chemistry. Today, carbamates make structural and/or functional part of many drugs and prodrugs approved and marketed for the treatment of various diseases such as cancer, epilepsy, hepatitis C, HIV infection, and Alzheimer's disease. In drugs they can play a role in drug-target interaction or improve the biological activity of parent molecules. In prodrugs they are mainly used to delay first-pass metabolism and enhance the bioavailability and effectiveness of compounds. This brief review takes a look at the properties and use of carbamates in various fields of medicine and provides quick insights into the mechanisms of action for some of them.

Anti-Tick-Borne Encephalitis Virus Activity of Novel Uridine Glycoconjugates Containing Amide or/and 1,2,3-Triazole Moiety in the Linker Structure

Tick-borne encephalitis virus (TBEV) transmitted by ticks is a pathogen of great medical importance. As still no effective antiviral treatment is available, in the present study, a series of uridine glycoconjugates containing amide or/and 1,2,3-triazole moiety in the linker structure was synthesized and evaluated for the antiviral activity against two strains of TBEV: a highly virulent Hypr strain and less virulent Neudoerfl strain, using standardized previously in vitro assays. Our data have shown that four compounds from the series (18–21) possess strong activity against both TBEV strains. The half maximal inhibitory concentration (IC₅₀) values of compounds 18–21 were between 15.1 and 3.7 μM depending on the virus strain, which along with low cytotoxicity resulted in high values of the selectivity index (SI). The obtained results suggest that these compounds may be promising candidates for further development of new therapies against flaviviruses.

Transition Metal-Free Synthesis of Carbamates Using CO2 as the Carbon Source

Utilization of carbon dioxide as a C1 synthon is highly attractive for the synthesis of valuable chemicals. However, activation of CO₂ is highly challenging, owing to its thermodynamic stability and kinetic inertness. With this in mind, several strategies have been developed for the generation of carbon-heteroatom bonds. Among these, formation of C-N bonds is highly attractive, especially, when carbamates can be synthesized directly from CO₂ . This Minireview focuses on transition metal-free approaches for the fixation of CO₂ to generate carbamates for the production of fine chemicals and pharmaceuticals. Within the past decade, transition metal-free approaches have gained increasing attention, but traditional reviews have rarely focused on these approaches. Direct comparisons between such methods have been even more scarce. This Minireview seeks to address this discrepancy.

Characterization and toxicity evaluation of degradation products of febantel

Background

The aim of the present work was to determine potential toxicity of degradation products of febantel generated under different stress conditions mentioned in guideline Q1A (R2) laid down by International Council for Harmonization (ICH). The stability behavior of febantel was studied by subjecting it to hydrolytic, oxidative, photolytic and thermal forced degradation conditions.

Results

Five degradation products (DPs) were observed which were resolved using high-performance liquid chromatography (HPLC) and characterized by LC-MS/MS using positive mode of electrospray ionization. The chromatographic separation was carried out on Hypersil® BDS C18 (150 × 4.6 mm, 5 μm) column. Optimum resolution was obtained using ammonium formate buffer (10 mM, pH 3.5) and acetonitrile programmed in gradient elution mode at 281.0 nm using photodiode array detector.

Conclusion

The drug was found susceptible to degradation under all the stress conditions except thermal and oxidative stress. Five major unknown degradation products DP–I, DP–II, DP–III, DP–IV, and DP–V generated under photolytic, alkali, and acidic stress condition were identified and characterized by LC-MS/MS. The drug and identified degradation products were screened for prediction of in-silico toxicity using software viz. Swiss ADME, OSIRIS Property Explorer and Pro Tox II which indicated overall no toxicological concerns.

Graphical abstract

Celastrol: A Review of Useful Strategies Overcoming its Limitation in Anticancer Application

Celastrol, a natural bioactive ingredient derived from Tripterygium wilfordii Hook F, exhibits significant broad-spectrum anticancer activities for the treatment of a variety of cancers including liver cancer, breast cancer, prostate tumor, multiple myeloma, glioma, etc. However, the poor water stability, low bioavailability, narrow therapeutic window, and undesired side effects greatly limit its clinical application. To address this issue, some strategies were employed to improve the anticancer efficacy and reduce the side-effects of celastrol. The present review comprehensively focuses on the various challenges associated with the anticancer efficiency and drug delivery of celastrol, and the useful approaches including combination therapy, structural derivatives and nano/micro-systems development. The specific advantages for the use of celastrol mediated by these strategies are presented. Moreover, the challenges and future research directions are also discussed. Based on this review, it would provide a reference to develop a natural anticancer compound for cancer treatment.

Cyanine Nanocages Activated by Near-Infrared Light for the Targeted Treatment of Traumatic Brain Injury

Traumatic brain injury (TBI) is a common and prevalent condition that affects large numbers of people across a range of ages. Individuals engaging in physical activities and victims of accidents are at a higher risk for TBI. There is a lack of available treatment specifically for TBI. Given the difficulty to determine its precise location in the brain, TBI remains difficult to fully diagnose or treat. Herein, we disclose a novel strategy for directing therapeutic agents to TBI sites, without the need to determine the precise location of the TBI activity in the brain. This novel approach is based on the use of a cyanine dye nanocage carrying Gabapentin, a known TBI therapeutic agent. Upon exposure of the cyanine nanocage to near-infrared light, the local release of Gabapentin is triggered, selectively at the TBI-affected site.

Cross-dehydrogenative Coupling Reactions Between Formamidic C(sp2)-H and X-H (X = C, O, N) Bonds

In the last decade, the scientific community has witnessed explosive growth in research on the direct carbamoylation of C-H and X-H (X = N, O) bonds with formamides via cross-dehydrogenative coupling reactions. This novel approach is an effective means of preparing a variety of carboxamide, carbamate as well as urea derivatives, which are prevalent in medicinal chemistry and natural product synthesis. This review elaborates the most important advances and developments in the field, with an emphasis on the reaction patterns and mechanisms.

A Pentacyclic Triterpene from Ligustrum lucidum Targets γ-Secretase

Amyloid-beta peptides generated by β-secretase- and γ-secretase-mediated successive cleavage of amyloid precursor protein are believed to play a causative role in Alzheimer's disease. Thus, reducing amyloid-beta generation by modulating γ-secretase remains a promising approach for Alzheimer's disease therapeutic development. Here, we screened fruit extracts of Ligustrum lucidum Ait. (Oleaceae) and identified active fractions that increase the C-terminal fragment of amyloid precursor protein and reduce amyloid-beta production in a neuronal cell line. These fractions contain a mixture of two isomeric pentacyclic triterpene natural products, 3-O-cis- or 3-O-trans-p-coumaroyl maslinic acid (OCMA), in different ratios. We further demonstrated that trans-OCMA specifically inhibits γ-secretase and decreases amyloid-beta levels without influencing cleavage of Notch. By using photoactivatable probes targeting the subsites residing in the γ-secretase active site, we demonstrated that trans-OCMA selectively affects the S1 subsite of the active site in this protease. Treatment of Alzheimer's disease transgenic model mice with trans-OCMA or an analogous carbamate derivative of a related pentacyclic triterpene natural product, oleanolic acid, rescued the impairment of synaptic plasticity. This work indicates that the naturally occurring compound trans-OCMA and its analogues could become a promising class of small molecules for Alzheimer's disease treatment.

Global trends in pesticides: A looming threat and viable alternatives

Pesticides are widely used chemical compounds in agriculture to destroy insects, pests and weeds. In modern era, they form an indispensable part of agricultural and health practices. Globally, nearly 3 billion kg of pesticides are used every year with a budget of ~40 billion USD. This extensive usage has increased the crop yield as well as led to significant reduction in harvest losses and thereby, enhanced food availability. On the other hand, indiscriminate usage of these chemicals has led to several environmental implications and caused adverse effects on human health. Epidemiological evidences have revealed the harmful effects of pesticides exposure on various organs including liver, brain, lungs and colon. Recent investigations have shown that pesticides can also lead to fatal consequences such as cancer among individuals. These chemicals enter ecosystem, thus hampering the sensitive environmental equilibrium through bio-accumulation. Due to their non-biodegradable nature, they can persist in nature for years and are regarded as potent biohazard. Worldwide, very few surveillance methods have been considered, which can bring awareness among the individuals, therefore the present review is an attempt to delineate consequences induced by various types of pesticide exposure on the environment. Further, the prospective of biopesticides use could facilitate the increase of crop production without compromising human health.

N-[3,5-Bis(trifluoromethyl)phenyl]-5-bromo-2-hydroxybenzamide Analogues: Novel Acetyl- and Butyrylcholinesterase Inhibitors

BACKGROUND

Development of acetyl- (AChE) and butyrylcholinesterase (BuChE) inhibitors belongs to viable strategies for the treatment of dementia and other diseases related to decrease in cholinergic neurotransmission.

OBJECTIVE

That is why we designed twenty-two analogues of a dual AChEBuChE salicylanilide inhibitor, N-[3,5-bis(trifluoromethyl)phenyl]-5-bromo-2-hydroxybenzamide 1, to improve its potency.

METHODS

We prepared N,N-disubstituted (thio)carbamates via direct acylation with (thio)carbamoyl chloride, N-n-alkyl monosubstituted carbamates using isocyanates as well as its salicylanilide core analogues. The derivatives were evaluated in vitro against AChE from electric eel and BuChE from equine serum using spectrophotometric Ellman's method.

RESULTS

The compounds showed moderate inhibition of both AChE and BuChE with IC50 from 18.2 to 196.6 μmol.L-1 and 9.2 to 196.2 μmol.L-1, respectively. Importantly, based on the substitution pattern, it is possible to modulate selectivity against AChE or BuChE and some derivatives also produced a balanced inhibition. In general, the most promising analogues were N-alkyl (C2-C6) carbamates and isomers with a changed position of phenolic hydroxyl. N-[3,5-Bis(trifluoromethyl)phenyl]-3-bromo-5- hydroxybenzamide 4a was the best inhibitor of both cholinesterases.

CONCLUSION

A wide range of the derivatives improved the activity of the hit 1, they were superior to carbamate drug rivastigmine against AChE and some of them also against BuChE. The most promising derivatives also fit physicochemical space and structural features for CNS drugs together with an escalated lipophilicity.

Nitroreductase-Mediated Release of Inhibitors of Lysine-Specific Demethylase 1 (LSD1) from Prodrugs in Transfected Acute Myeloid Leukaemia Cells

Lysine-specific demethylase 1 (LSD1) has evolved as a promising therapeutic target for cancer treatment, especially in acute myeloid leukaemia (AML). To approach the challenge of site-specific LSD1 inhibition, we developed an enzyme-prodrug system with the bacterial nitroreductase NfsB (NTR) that was expressed in the virally transfected AML cell line THP1-NTR+ . The cellular activity of the NTR was proven with a new luminescent NTR probe. We synthesised a diverse set of nitroaromatic prodrugs that by design do not affect LSD1 and are reduced by the NTR to release an active LSD1 inhibitor. The emerging side products were differentially analysed using negative controls, thereby revealing cytotoxic effects. The 2-nitroimidazolyl prodrug of a potent LSD1 inhibitor emerged as one of the best prodrug candidates with a pronounced selectivity window between wild-type and transfected THP1 cells. Our prodrugs are selectively activated and release the LSD1 inhibitor locally, proving their suitability for future targeting approaches.

Chemistry of Renieramycins. Part 19: Semi-Syntheses of 22-O-Amino Ester and Hydroquinone 5-O-Amino Ester Derivatives of Renieramycin M and Their Cytotoxicity against Non-Small-Cell Lung Cancer Cell Lines

Two new series of synthetic renieramycins including 22-O-amino ester and hydroquinone 5-O-amino ester derivatives of renieramycin M were semi-synthesized and evaluated for their cytotoxicity against the metastatic non-small-cell lung cancer H292 and H460 cell lines. Interestingly, the series of 22-O-amino ester derivatives displayed a potent cytotoxic activity greater than the hydroquinone derivatives. The most cytotoxic derivative of the series was the 22-O-(N-Boc-l-glycine) ester of renieramycin M (5a: IC₅₀ 3.56 nM), which showed 7-fold higher potency than renieramycin M (IC₅₀ 24.56 nM) and 61-fold more than jorunnamycin A (IC₅₀ 217.43 nM) against H292 cells. In addition, 5a exhibited a significantly higher cytotoxic activity than doxorubicin (ca. 100 times). The new semi-synthetic renieramycin derivatives will be further studied and developed as potential cytotoxic agents for non-small-cell lung cancer treatment.

Amide Bond Bioisosteres: Strategies, Synthesis, and Successes

The amide functional group plays a key role in the composition of biomolecules, including many clinically approved drugs. Bioisosterism is widely employed in the rational modification of lead compounds, being used to increase potency, enhance selectivity, improve pharmacokinetic properties, eliminate toxicity, and acquire novel chemical space to secure intellectual property. The introduction of a bioisostere leads to structural changes in molecular size, shape, electronic distribution, polarity, pK_a, dipole or polarizability, which can be either favorable or detrimental to biological activity. This approach has opened up new avenues in drug design and development resulting in more efficient drug candidates introduced onto the market as well as in the clinical pipeline. Herein, we review the strategic decisions in selecting an amide bioisostere (the why), synthetic routes to each (the how), and success stories of each bioisostere (the implementation) to provide a comprehensive overview of this important toolbox for medicinal chemists.

Scaffolding-Induced Property Modulation of Chemical Space

Physicochemical property switching of chemical space is of great importance for optimization of compounds, for example, for biological activity. Cyclization is a key method to control 3D and other properties. A two-step approach, which involves a multicomponent reaction followed by cyclization, is reported to achieve the transition from basic moieties to charge neutral cyclic derivatives. A series of multisubstituted oxazolidinones, oxazinanones, and oxazepanones as well as their thio and sulfur derivatives are synthesized from readily available building blocks with mild conditions and high yields. Like a few other methods, MCR and cyclization allow for the collective transformation of a large chemical space into a related one with different properties.

Potential Moracin M Prodrugs Strongly Attenuate Airway Inflammation In Vivo

This study aims to develop new potential therapeutic moracin M prodrugs acting on lung inflammatory disorders. Potential moracin M prodrugs (KW01-KW07) were chemically synthesized to obtain potent orally active derivatives, and their pharmacological activities against lung inflammation were, for the first time, examined in vivo using lipopolysaccharide (LPS)-induced acute lung injury model. In addition, the metabolism of KW02 was also investigated using microsomal stability test and pharmacokinetic study in rats. When orally administered, some of these compounds (30 mg/kg) showed higher inhibitory action against LPSinduced lung inflammation in mice compared to moracin M. Of them, 2-(3,5-bis((dimethylcarbamoyl)oxy)phenyl)benzofuran-6-yl acetate (KW02) showed potent and dose-dependent inhibitory effect on the same animal model of lung inflammation at 1, 3, and 10 mg/kg. This compound at 10 mg/kg also significantly reduced IL-1β concentration in the bronchoalveolar lavage fluid of the inflamed-lungs. KW02 was rapidly metabolized to 5-(6-hydroxybenzofuran-2-yl)-1,3-phenylene bis(dimethylcarbamate) (KW06) and moracin M when it was incubated with rat serum and liver microsome as expected. When KW02 was administered to rats via intravenous or oral route, KW06 was detected in the serum as a metabolite. Thus, it is concluded that KW02 has potent inhibitory action against LPS-induced lung inflammation. It could behave as a potential prodrug of moracin M to effectively treat lung inflammatory disorders.

Insight into antimicrobial activity of substituted phenylcarbamoyloxypiperazinylpropanols

3-[4-(Substituted)phenyl-/4-(diphenylmethyl)phenylpiperazin-1-yl]-2-hydroxypropyl-1-[(substituted)phenyl]carbamates and their salts with hydrochloric acid were synthesized, characterized, and tested in vitro against Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 as reference and quality control strains, against three methicillin-resistant isolates of S. aureus, and three isolates of vancomycin-resistant E. faecalis. All the compounds were evaluated against Mycobacterium tuberculosis H₃₇R_a/ATCC 25177, M. kansasii DSM 44162, and M. smegmatis ATCC 700084. All of the tested compounds demonstrated very good activity against all the tested strains/isolates comparable with or better than that of clinically used drugs (ampicillin, ciprofloxacin, vancomycin, isoniazid). 1-[{(3-Trifluoromethyl)phenyl}carbamoyloxy-2-hydroxypropyl]-4-(3,4-dichlorophenyl)piperazin-1-ium chloride demonstrated the highest potency against all the tested strains/isolates (MICs ranged from 3.78 to 30.2 µM), and 1-[{(3-trifluoromethyl)phenyl}carbamoyloxy-2-hydroxypropyl]-4-(diphenylmethyl)piperazin-1-ium chloride was the most effective against all the screened mycobacterial strains (MICs ranged from 3.64 to 14.5 µM). All the investigated derivatives had strong antibiofilm activity against S. aureus ATCC 29123 and a synergistic or additive effect with gentamicin against isolates of E. faecalis with both intrinsic and acquired resistance to gentamicin. The screening of the cytotoxicity of the compounds was performed using human monocytic leukemia THP-1 cells. The IC₅₀ values of the most effective compounds ranged from ca. 2.8 to 7.3 µM; thus, it can be stated that the antimicrobial effect is closely connected with their cytotoxicity. These observations disqualify these compounds from further development as antimicrobial agents, but they can be considered potential multi-target drugs with a preferred anticancer effect with good water solubility and additional anti-infectious activity.

Microwave-assisted One-pot Synthesis of Amide Bond using WEB

Background:

Amide bond plays a key role in medicinal chemistry, and the analysis of bioactive molecular database revealed that the carboxamide group appears in more than 25% of the existing database drugs. Typically amide bonds are formed from the union of carboxylic acid and amine; however, the product formation does not occur spontaneously. Several synthetic methods have been reported for amide bond formation in literature. Present work demonstrated simple and eco-friendly amide bond formation using carboxylic acid and primary amines through in situ generation of O-acylurea. The reaction was found to be more efficient, faster reaction rate; simple work-up gave pure compound isolation in moderate to excellent yield using microwave irradiation as compared to conventional heating.

Methods:

Developed one-pot synthesis of amide compounds using agro-waste derived greener catalyst under microwave irradiation.

Results:

Twenty amide bond containing organic compounds are synthesized from carboxylic acid with primary amine catalyzed by agro-waste derived medium under microwave irradiation. First, the reaction involved carboxylic acid activation using EDC.HCl, which is the required base for the neutralization and coupling. The method employed natural agro-waste derived from banana peel ash (WEB) for the coupling gave target amide product without the use of an external organic or inorganic base.

Conclusion:

In the present work, we demonstrated that agro-waste extract is an alternative greener catalytic medium for the condensation of organic carboxylic acid and primary amine under microwave irradiation. The method found several advantages compared to reported methods like solventfree, non-toxic, cheaper catalyst, and simple reaction condition. The final isolated product achieved chromatographically pure by simple recrystallization and did not require further purification.

Dimeric γ-AApeptides With Potent and Selective Antibacterial Activity

Over the past few decades, the emergence of antibiotic resistance developed by life-threatening bacteria has become increasingly prevalent. Thus, there is an urgent demand to develop novel antibiotics capable of mitigating this trend. Herein, we report a series of dimeric γ-AApeptide derivatives as potential antibiotic agents with limited toxicity and excellent selectivity against Gram-positive strains. Among them, compound 2 was identified to have the best MICs without inducing drug resistance, even after exposure to MRSA for 20 passages. Time-kill kinetics and mechanistic studies suggested that 2 could mimic host-defense peptides (HDPs) and rapidly eradicate MRSA within 2 hours through disturbing the bacteria membrane. Meanwhile, biofilm formation was successfully inhibited even at a low concentration. Taken together, these results suggested the great potential of dimeric γ-AApeptide derivatives as antibacterial agents.

Metabolism and in vitro drug-drug interaction assessment of viloxazine

Viloxazine is currently being developed as a treatment for attention deficit/hyperactivity disorder (ADHD). The aim of these studies is to update the understanding of the rat and human metabolism and the in vitro drug-drug interaction profile of viloxazine to a degree where it meets current regulatory standards for such investigations. In vivo absorption-distribution-metabolism-excretion (ADME) studies demonstrated that in humans 5-hydroxylation followed by glucuronidation is the major metabolic route. This route was also seen as a minor route in rats where the major route is O-deethylation with subsequent sulfation. In humans, the 5-hydoxylation pathway is mediated by CYP2D6. An estimate for the fraction of the metabolism via this pathway suggests a PM/EM difference of <2-fold, making it highly unlikely that this will be an issue of clinical significance. Viloxazine forms a unique N-carbamoyl glucuronide in humans. The chemical reactivity characteristics of this metabolite are similar to stable glucuronide conjugates and dissimilar from acyl glucuronides; therefore, it is regarded as a stable Phase II conjugate. In vitro drug-drug interaction (DDI) testing indicates that viloxazine is not a significant inhibitor or inducer of CYPs and transporters with the exception of CYP1A2.

Platinum-Triggered Bond-Cleavage of Pentynoyl Amide and N-Propargyl Handles for Drug-Activation

The ability to create ways to control drug activation at specific tissues while sparing healthy tissues remains a major challenge. The administration of exogenous target-specific triggers offers the potential for traceless release of active drugs on tumor sites from antibody–drug conjugates (ADCs) and caged prodrugs. We have developed a metal-mediated bond-cleavage reaction that uses platinum complexes [K₂PtCl₄ or Cisplatin (CisPt)] for drug activation. Key to the success of the reaction is a water-promoted activation process that triggers the reactivity of the platinum complexes. Under these conditions, the decaging of pentynoyl tertiary amides and N-propargyls occurs rapidly in aqueous systems. In cells, the protected analogues of cytotoxic drugs 5-fluorouracil (5-FU) and monomethyl auristatin E (MMAE) are partially activated by nontoxic amounts of platinum salts. Additionally, a noninternalizing ADC built with a pentynoyl traceless linker that features a tertiary amide protected MMAE was also decaged in the presence of platinum salts for extracellular drug release in cancer cells. Finally, CisPt-mediated prodrug activation of a propargyl derivative of 5-FU was shown in a colorectal zebrafish xenograft model that led to significant reductions in tumor size. Overall, our results reveal a new metal-based cleavable reaction that expands the application of platinum complexes beyond those in catalysis and cancer therapy.

Design, synthesis and evaluation of carbamate-linked uridyl-based inhibitors of human ST6Gal I

Sialic acid at the terminus of cell surface glycoconjugates is a critical element in cell-cell recognition, receptor binding and immune responses. Sialyltransferases (ST), the enzymes responsible for the biosynthesis of sialylated glycans are highly upregulated in cancer and the resulting hypersialylation of the tumour cell surface correlates strongly with tumour growth, metastasis and drug resistance. Inhibitors of human STs, in particular human ST6Gal I, are thus expected to be valuable chemical tools for the discovery of novel anticancer drugs. Herein, we report on the computationally-guided design and development of uridine-based inhibitors that replace the charged phosphodiester linker of known ST inhibitors with a neutral carbamate to improve pharmacokinetic properties and synthetic accessibility. A series of 24 carbamate-linked uridyl-based compounds were synthesised by coupling aryl and hetaryl α-hydroxyphosphonates with a 5'-amino-5'-deoxyuridine fragment. The inhibitory activities of the newly synthesised compounds against recombinant human ST6Gal I were determined using a luminescent microplate assay, and five promising inhibitors with K_i's ranging from 1 to 20 µM were identified. These results show that carbamate-linked uridyl-based compounds are a potential new class of readily accessible, non-cytotoxic ST inhibitors to be further explored.

A One-Pot Iodo-Cyclization/Transition Metal-Catalyzed Cross-Coupling Sequence: Synthesis of Substituted Oxazolidin-2-ones from N-Boc-allylamines

A one-pot iodo-cyclization/transition metal-catalyzed cross-coupling sequence is reported to access various C5-functionalized oxazolidin-2-ones from unsaturated N-Boc-allylamines. Depending on the Grignard reagents used for the cross-coupling, e.g., aryl- or cyclopropylmagnesium bromide, a cobalt or copper catalyst has to be used to obtain the functionalized oxazolidin-2-ones in good yields.