Recent Advances in the Synthesis of Hydantoins: The State of the Art of a Valuable Scaffold

Cultivation technology optimization and identification of secondary metabolites from elm oyster mushroom Hypsizygus ulmarius (Bull.) Redhead (Agaricomycetes) through GC-MS metabolomic profiling from India

Hypsizygus ulmarius, a novel oyster mushroom species, offers potential scope due to its low-cost production, high biological efficiency, and notable nutritional, medicinal, and therapeutic properties. The present study standardized commercial cultivation technology for H. ulmarius in the Trans-Gangetic Plains of India. The mycelium grew well on potato dextrose agar and carrot extract broth at pH 8.0 and temperature 25 C. Wheat straw supplemented with the cotton seed hull at the rate of 10.0% dose, spawned with pearl millet grain spawn at the rate of 5.0% spawn dose, gave the highest mushroom yield (953.66 g/0.4 kg dry substrate) with biological efficiency (238.41%). The first flush sporocarps were freeze-dried for physicochemical characterization, revealing 16 strong peaks and 8 functional groups via Fourier transform infrared (FTIR) analysis. Particle size averaged 45.97 µm of mushroom powder, and scanning electron microscopy (SEM) analysis showed diverse surface textures. Gas chromatography-mass spectrometry metabolic profiling identified 20 key secondary metabolites each from hexane and methanolic extracts, with therapeutic uses that are valuable for pharmaceutical, nutraceutical, and food industry applications.

Configurationally labile α-bromoacid derivatives for asymmetric preparation of heterocycles

α-Bromoacid derivatives are configurationally labile under various conditions, and the dynamic resolution of them has been recognized as an effective strategy in asymmetric synthesis. This article is a concise review of our efforts on the heteroannulation of α-bromoacid derivatives through nucleophilic substitution and subsequent ring formation with diverse carbon, nitrogen, oxygen, and sulfur nucleophiles. Chiral auxiliary (Xc)-bound α-bromoacid derivatives serve as versatile chiral building blocks for the direct incorporation of a two-carbon unit in cyclization reactions. Eight readily available chiral auxiliaries are investigated and identified to be suitable for the dynamic resolution of α-bromoacid derivatives. We have presented selected results about three distinct dynamic resolutions such as dynamic kinetic resolution (DKR), dynamic thermodynamic resolution (DTR) and crystallization induced dynamic resolution (CIDR) that have been successfully employed in the asymmetric synthesis of fourteen different scaffolds of six- or five-membered heterocycles.

Light-Induced Reactivity of Nucleophilic Siloxycarbene with Heterocumulenes: Synthesis of α-Ketoamides, Hydantoins, Oxoacetamidines, and Amides

We report the reactivity of in situ-generated nucleophilic siloxycarbenes from acylsilanes via the 1,2-Brook rearrangement in the presence of visible light with heterocumulenes. This method significantly advances from the conventional use of electrophilic carbenes stabilized by metal catalysts and harsh reaction conditions. The reactivity was explored with isocyanates, carbodiimides, and N-sulfinylamines to synthesize α-ketoamides, hydantoins, oxoacetamidines, and amides. In addition, this work demonstrated the synthetic utility and synthesis of biologically active molecules. Moreover, mechanistic insights reveal that this reaction proceeds through a singlet carbene mechanism.

Synthesis, carbonic anhydrase inhibition studies and modelling investigations of phthalimide-hydantoin hybrids

A novel series of hydantoins incorporating phthalimides has been synthesised by condensation of activated phthalimides with 1-aminohydantoin and investigated for their inhibitory activity against a panel of human (h) carbonic anhydrase (CA, EC 4.2.1.1): the cytosolic isoforms hCA I, hCA II, and hCA VII, secreted isoform hCA VI, and the transmembrane hCA IX, by a stopped-flow CO2 hydrase assay. Although all newly developed compounds were totally inactive on hCA I and mainly ineffective towards hCA II, they generally exhibited moderate repressing effects on hCA VI, VII, and IX with KIs values in the submicromolar to micromolar ranges. The salts 3a and 3b, followed by derivative 5, displayed the best inhibitory activity of all the evaluated compounds and their binding mode was proposed in silico. These compounds can also be considered interesting starting points for the development of novel pharmacophores for this class of enzyme inhibitors.

Azocarboxamide-enabled enantioselective regiodivergent unsymmetrical 1,2-diaminations

Enantioenriched unsymmetrical vicinal diamines are important basic structural motifs. While catalytic asymmetric intermolecular 1,2-diamination of carbon-carbon double bonds represents the most straightforward approach for preparing enantioenriched vicinal-diamine-containing heterocycles, these reactions are often limited to the installation of undifferentiated amino functionalities through metal catalysis and/or the use of stoichiometric amounts of oxidants. Here, we report organocatalytic enantioselective unsymmetrical 1,2-diaminations based on the rational design of a bifunctional 1,2-diamination reagent, namely, azocarboxamides (ACAs). Under the catalysis of chiral phosphoric acid, unsymmetrical 1,2-diaminations of ACAs with various electron-rich double bonds readily occur in a regiodivergent manner. Indoles prefer dual hydrogen-bonding mode to give dearomative (4 + 2) products, and 3-vinylindoles and azlactones are inclined to undergo unsymmetrical 1,2-diamination via the (3 + 2) process. DFT calculations are performed to reveal the reaction mechanism and the origin of the regio- and enantioselectivity. Guided by computational design, we are able to reverse the regioselectivity of the dearomative unsymmetrical 1,2-diamination of indoles using Lewis acid catalysis.

Base-Promoted Aminoamidation of Cinnamoyl Chlorides with Aryl Amines: Access to β-Amino Amides

Herein, a base-promoted strategy for the synthesis of β-amino acids derivatives from α,β-unsaturated acyl chlorides derivatives and aryl amines has been described. In the presence of triethylamine, a tandem Michael addition and nucleophilic substitution progress was generated. The current method features readily available raw materials, mild reaction conditions, high atom economy, and wide tolerance for the coupling partners.

(Dimethylamino)methylene hydantoins as building blocks in the synthesis of oxoaplysinopsins and parabanic acids with antifungal activity

A short, efficient, and stereoselective methodology is described for the synthesis of 5-((dimethylamino)methylene)hydantoins and their conversion into oxoaplysinopsins and parabanic acids. A highly convergent one-pot, two-step reaction between methyl N-arylglycinates, isocyanates, and DMFDMA under microwave irradiation provided the corresponding (dimethylamino)methylene hydantoins as a single E-stereoisomer in high overall yields. The synthesis of (S)-1-(1-phenylethyl) chiral hydantoins, which undergo a stereoselective addition of acetic anhydride, aza-heterocycles, and amines, received special attention. The reaction with indole delivered a series of novel oxoaplysinopsins. Meanwhile, parabanic acids were prepared by a new approach, treating (dimethylamino)methylene hydantoins with mCPBA to generate the oxidative fragmentation of the exocyclic methylene. The antifungal evaluation of the prepared products was carried out on a series of Candida spp., finding potent growth inhibition. According to previous docking studies, this activity is probably due to the inhibitory interaction of the derivatives with the active site of the fungal HMGR enzyme.

Synthesis, Absolute Configuration, Biological Profile and Antiproliferative Activity of New 3,5-Disubstituted Hydantoins

Hydantoins, a class of five-membered heterocyclic compounds, exhibit diverse biological activities. The aim of this study was to synthesize and characterize a series of novel 3,5-disubstituted hydantoins and to investigate their antiproliferative activity against human cancer cell lines. The new hydantoin derivatives 5a-i were prepared as racemic mixtures of syn- and anti-isomers via a base-assisted intramolecular amidolysis of C-3 functionalized β-lactams. The enantiomers of syn-5a and anti-hydantoins 5b were separated by preparative high-performance liquid chromatography (HPLC) using n-hexane/2-propanol (90/10, v/v) as the mobile phase. The absolute configuration of the four allyl hydantoin enantiomers 5a was assigned based on a comparison of the experimental electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) spectra with those calculated using density functional theory (DFT). The antiproliferative activity evaluated in vitro against three different human cancer cell lines: HepG2 (liver hepatocellular carcinoma), A2780 (ovarian carcinoma), and MCF7 (breast adenocarcinoma), and on the non-tumor cell line HFF1 (normal human foreskin fibroblasts) using the MTT cell proliferation assay. In silico drug-like properties and ADMET profiles were estimated using the ADMET Predictor ver. 9.5 and the online server admetSAR. Eighteen new 3,5-disubstituted hydantoins were synthesized and characterized. The compound anti-5c showed potent cytotoxic activity against the human tumor cell line MCF7 (IC50 = 4.5 µmol/L) and the non-tumor cell line HFF1 (IC50 = 12.0 µmol/L). In silico analyzes revealed that the compounds exhibited moderate water solubility and membrane permeability and are likely substrates for CYP3A4 and P-glycoprotein and have a high probability of antiarthritic activity.

Cycloadditions of 5-Vinyloxazolidine-2,4-diones: A Straightforward Access to the (Thio)hydantoin Scaffold

A palladium-catalyzed (3 + 2) cycloaddition between 5-vinyloxazolidine-2,4-diones (VOxD) and (thio)isocyanates is described. Under optimized conditions, an array of (thio)hydantoins was readily prepared, and an enantioselective version of this transformation was then studied. To illustrate the importance of this method, a concise synthesis of two bioactive compounds, nirvanol and mephenytoin, was carried out. This work emphasizes the synthetic potential of VOxD as useful precursors of zwitterionic aza-π-allylpalladiumII intermediates.

13 Cβ-Valine and 13 Cγ-Leucine Methine Labeling To Probe Protein Ligand Interaction

Precise information regarding the interaction between proteins and ligands at molecular resolution is crucial for effectively guiding the optimization process from initial hits to lead compounds in early stages of drug development. In this study, we introduce a novel aliphatic side chain isotope-labeling scheme to directly probe interactions between ligands and aliphatic sidechains using NMR techniques. To demonstrate the applicability of this method, we selected a set of Brd4-BD1 binders and analyzed 1 H chemical shift perturbation resulting from CH-π interaction of Hβ -Val and Hγ -Leu as CH donors with corresponding ligand aromatic moieties as π acceptors.

A Tunable Cascade Reaction of Ureidomalonates and Alkenyl Azlactones for the Divergent Synthesis of Hydantoins with Distinct Functional Groups

A tunable cascade reaction of ureidomalonates and alkenyl azlactones was disclosed, which gave rise to the construction of N-aroyl α-amino acid ester and imide-functionalized hydantoins in moderate to good yields and with excellent diastereoselectivities. The reaction pathway was precisely manipulated by organocatalysis and phase-transfer/sunlight relay catalysis, respectively, to realize the divergent synthesis. The successful gram-scale preparation of representative products exhibited the application potential of this protocol. Mechanistic studies indicated that the exchange and phase transfer of ethoxy anion played a key role in altering the reaction pathway, and sunlight might accelerate the oxidation process at the late stage of the reaction triggered by phase-transfer catalysis.

Structure-Activity Relationship Study and Design Strategies of Hydantoin, Thiazolidinedione, and Rhodanine-Based Kinase Inhibitors: A Two-Decade Review

Cancer is one of the most prominent causes of the rapidly growing mortality numbers worldwide. Cancer originates from normal cells that have acquired the capability to alter their molecular, biochemical, and cellular traits. The alteration of cell signaling enzymes, such as kinases, can initiate and amplify cancer progression. As a curative method, the targeted therapy utilized small molecules' capability to inhibit kinase's cellular function. This review provides a brief history (1999-2023) of Small Molecule Kinase Inhibitors (SMKIs) discovery with their molecular perspective. Furthermore, this current review also addresses the application and the development of hydantoin, thiazolidinedione, and rhodanine-based derivatives as kinase inhibitors toward several subclasses (EGFR, PI3K, VEGFR, Pim, c-Met, CDK, IGFR, and ERK) accompanied by their structure-activity relationship study and their molecular interactions. The present work summarizes and compiles all the important structural information essential for developing hydantoin, thiazolidinedione, and rhodanine-based kinase inhibitors to improve their potency in the future.

Collective Synthesis of Sarpagine and Macroline Alkaloid-Inspired Compounds

Design strategies that can access natural-product-like chemical space in an efficient manner may facilitate the discovery of biologically relevant compounds. We have employed a divergent intermediate strategy to construct an indole alkaloid-inspired compound collection derived from two different molecular design principles, i.e. biology-oriented synthesis and pseudo-natural products. The divergent intermediate was subjected to acid-catalyzed or newly discovered Sn-mediated conditions to selectively promote intramolecular C- or N-acylation, respectively. After further derivatization, a collection totalling 84 compounds representing four classes was obtained. Morphological profiling via the cell painting assay coupled with a subprofile analysis showed that compounds derived from different design principles have different bioactivity profiles. The subprofile analysis suggested that a pseudo-natural product class is enriched in modulators of tubulin, and subsequent assays led to the identification of compounds that suppress in vitro tubulin polymerization and mitotic progression.

Catalytic Photochemical Deracemization via Short-Lived Intermediates

Upon irradiation in the presence of a suitable chiral catalyst, racemic compound mixtures can be converted into enantiomerically pure compounds with the same constitution. The process is called photochemical deracemization and involves the formation of short-lived intermediates. By opening different reaction channels for the forward reaction to the intermediate and for the re-constitution of the chiral molecule, the entropically disfavored process becomes feasible. Since the discovery of the first photochemical deracemization in 2018, the field has been growing rapidly. This review comprehensively covers the research performed in the area and discusses current developments. It is subdivided according to the mode of action and the respective substrate classes. The focus of this review is on the scope of the individual reactions and on a discussion of the mechanistic details underlying the presented reaction.

Chiral, air stable, and reliable Pd(0) precatalysts applicable to asymmetric allylic alkylation chemistry

Stereoselective carbon-carbon bond formation via palladium-catalyzed asymmetric allylic alkylation is a crucial strategy to access chiral natural products and active pharmaceutical ingredients. However, catalysts based on the privileged Trost and Pfaltz-Helmchen-Williams PHOX ligands often require high loadings, specific preactivation protocols, and excess chiral ligand. This makes these reactions uneconomical, often unreproducible, and thus unsustainable. Here we report several chiral single-component Pd(0) precatalysts that are active and practically-applicable in a variety of asymmetric allylic alkylation reactions. Despite the decades-long history and widespread use of Trost-type ligands, the precatalysts in this work are the only reported examples of stable, isolable Pd(0) complexes with these ligands. Evaluating these precatalysts across nine asymmetric allylic alkylation reactions reveals high reactivity and selectivity at low Pd loading. Importantly, we also report an unprecedented Pd-catalyzed enantioselective allylation of a hydantoin, achieved on gram scale in high yield and enantioselectivity with only 0.2 mol% catalyst.

Catalytic Enantioselective Biltz Synthesis

The Biltz synthesis establishes straightforward access to 5,5-disubstituted (thio)hydantoins by combining a 1,2-diketone and a (thio)urea. Its appealing features include inherent atom and step economy together with the potential to generate structurally diverse products. However, control of the stereochemistry of this reaction has proven to be a daunting challenge. Herein, we describe the first example of enantioselective catalytic Biltz synthesis which affords more than 40 thiohydantoins with high stereo- and regio-control, irrespective of the symmetry of thiourea structure. A one pot synthesis of corresponding hydantoins is also documented. Remarkably, experimental studies and DFT calculations establish the reaction pathway and origin of stereoselectivity.

Turn-Mimic Hydantoin-Based Loops Constructed by a Sequential Multicomponent Reaction

A collection of peptidomimetics characterized by having an aspartic acid motif embedded in a rigid hydantoin heterocycle are synthesized through a sequential multicomponent domino process followed by standard regioselective deprotection/coupling reactions based on acid-base liquid/liquid purification protocols. 1H nuclear magnetic resonance experiments, molecular modeling, and X-ray analysis showed that the resulting hydantoin-based loops I (in particular) and II (to a lesser extent) can be considered novel β-turn inducer motifs being able to project two peptide-like strands in a U-shaped conformation driven by the formation of intermolecular hydrogen bonds.

Synthesis of Tetracyclic Spirooxindolepyrrolidine-Engrafted Hydantoin Scaffolds: Crystallographic Analysis, Molecular Docking Studies and Evaluation of Their Antimicrobial, Anti-Inflammatory and Analgesic Activities

In a sustained search for novel potential drug candidates with multispectrum therapeutic application, a series of novel spirooxindoles was designed and synthesized via regioselective three-component reaction between isatin derivatives, 2-phenylglycine and diverse arylidene-imidazolidine-2,4-diones (Hydantoins). The suggested stereochemistry was ascertained by an X-ray diffraction study and NMR spectroscopy. The resulting tetracyclic heterocycles were screened for their in vitro and in vivo anti-inflammatory and analgesic activity and for their in vitro antimicrobial potency. In vitro antibacterial screening revealed that several derivatives exhibited remarkable growth inhibition against different targeted microorganisms. All tested compounds showed excellent activity against the Micrococccus luteus strain (93.75 µg/mL ≤ MIC ≤ 375 µg/mL) as compared to the reference drug tetracycline (MIC = 500 µg/mL). Compound 4e bearing a p-chlorophenyl group on the pyrrolidine ring exhibited the greatest antifungal potential toward Candida albicans and Candida krusei (MIC values of 23.43 µg/mL and 46.87 µg/mL, respectively) as compared to Amphotericin B (MIC = 31.25 and 62.50 µg/mL, respectively). The target compounds were also tested in vitro against the lipoxygenase-5 (LOX-5) enzyme. Compounds 4i and 4l showed significant inhibitory activity with IC50 = 1.09 mg/mL and IC50 = 1.01 mg/mL, respectively, more potent than the parent drug, diclofenac sodium (IC50 = 1.19 mg/mL). In addition, in vivo evaluation of anti-inflammatory and analgesic activity of these spirooxindoles were assessed through carrageenan-induced paw edema and acetic acid-induced writhing assays, respectively, revealing promising results. In silico molecular docking and predictive ADMET studies for the more active spirocompounds were also carried out.

Brønsted Base-Catalyzed Enantioselective α-Functionalization of Carbonyl Compounds Involving π-Extended Enolates

Chiral Brønsted base (BB) catalyzed asymmetric transformations constitute an important tool for synthesis. A meaningful fraction of these transformations proceeds through transiently generated enolate intermediates, which display quite versatile reactivity against a variety of electrophiles. Some years ago, our group became interested in developing BB-catalyzed asymmetric reactions of enolizable carbonyl substrates that involve π-extended enolates in which, besides control of reaction diastereo and enantioselectivity, the site-selectivity control is an additional issue in most cases. In the examples covered in this account the opportunities deployed, and the challenges posed, by these methods are illustrated, with a focus on the generation of quaternary carbon stereocenters. In the way, new bifunctional BB catalysts as well as achiral templates were developed that may find further applications.

Green metrics in mechanochemistry

The development of new green methodologies and their broader adoption for promoting sustainable development in chemistry laboratories and industry play a significant role in society, due to the economic importance of chemistry and its widespread presence in everyday life. Therefore, a sustainable approach to chemistry contributes to the well-being of the worldwide population and complies with the United Nations Sustainable Development Goals (UN SDGs) and the European Green Deal. The review highlights how batch and continuous mechanochemical methods are an eco-friendly approach for organic synthesis, with a lower environmental footprint in most cases, compared to solution-based procedures. The assessment is objectively based on the use of green metrics (e.g., atom and real atom economy, E-factor, process mass intensity, material parameter recovery, Eco-scale, stoichiometric factor, etc.) and indicators (e.g. DOZN tool and life cycle assessment, LCA, studies) applied to organic transformations such as synthesis of the amide bond, carbamates, heterocycles, active pharmaceutical ingredients (APIs), porphyrins, porous organic polymers (POPs), metal- or acid-catalysed processes, multicomponent and condensation reactions, rearrangements, etc. The generalized absence of bulk solvents, the precise control over the stoichiometry (i.e., using agents in a stoichiometrically rather than in excess), and the more selective reactions enabling simplified work-up procedures are the distinctive factors, marking the superiority of mechanochemical processes over solution-based chemistry.

Synthesis and Conformational Analysis of Hydantoin-Based Universal Peptidomimetics

The synthesis of a collection of enantiomerically pure, systematically substituted hydantoins as structural privileged universal mimetic scaffolds is presented. It relies on a chemoselective condensation/cyclization domino process between isocyanates of quaternary or unsubstituted α-amino esters and N-alkyl aspartic acid diesters followed by standard hydrolysis/coupling reactions with amines, using liquid-liquid acid/base extraction protocols for the purification of the intermediates. Besides the nature of the α carbon on the isocyanate moiety, either a quaternary carbon or a more flexible methylene group, conformational studies in silico (molecular modeling), in solution (NMR, circular dichroism (CD), Fourier transform infrared (FTIR)), and in solid state (X-ray) showed that the presented hydantoin-based peptidomimetics are able to project their substituents in positions superimposable to the side chains of common protein secondary structures such as α-helix and β-turn, being the open α-helix conformation slightly favorable according to molecular modeling, while the closed β-turn conformation preferred in solution and in solid state.

Enantioselective synthesis of hydantoins by chiral acid-catalysed condensation of glyoxals and ureas

Hydantoins are important scaffolds in natural products and pharmaceuticals, with only a few synthetic strategies available for their asymmetric preparation. We herein describe a single-step enantioselective synthesis of 5-monosubstituted hydantoins via condensation of glyoxals and ureas in the presence of a chiral phosphoric acid at room temperature. Products were formed in up to 99% yield and 98 : 2 e.r. Using mechanistic and kinetic studies, including time course ¹H NMR monitoring, we revealed that the reaction likely proceeds via face-selective protonation of an enol-type intermediate.

C-Terminal-Modified Oligourea Foldamers as a Result of Terminal Methyl Ester Reactions under Alkaline Conditions

Hybrids of short oligourea foldamers with residues of α, β and γ-amino acids esters at the C-terminus were obtained and subjected to a reaction with LiOH. There are two possible transformations under such conditions, one of which is ester hydrolysis and the formation of a carboxylic group and the other is the cyclization reaction after abstraction of a proton from urea by a base. We have investigated this reaction with difference C-terminal residue structures, as well as under different work-up conditions, especially for oligourea hybrids with α-amino acid esters. For these compounds, an oligourea-hydantoin combination is the product of cyclization. The stability of the hydantoin ring under alkaline conditions has been alsotested. Furthermore, this work reports data related to the structure of C-terminal-modified oligourea foldamers in solution and, for one compound, in the solid state. Helical folding is preserved both for cyclized and linear modifications, with oligourea-acid hybrids appearing to be more conformationally stable, as they are stabilized by an additional intramolecular hydrogen bond in comparison to cyclic derivatives.

Organocatalytic cascade nucleophilic/aza-Michael addition reactions: metal-free catalytic strategy for the synthesis of hydantoins

Lewis base-catalyzed cascade nucleophilic/aza-Michael addition reaction of N-alkoxy β-oxo-acrylamides with isocyanates has been developed to afford various highly functionalized hydantoin derivatives in 80-98% yields under mild reaction conditions. The intriguing features of this method include metal-free reaction conditions, low catalyst loading, broad substrate scope and short reaction time.

Enantioselective and Chemoselective Phosphine Oxide-catalyzed Aldol Reactions of N-Unprotected Cyclic Carboxyimides

Asymmetric catalytic transformations of N-unprotected cyclic carboxyimides such as succinimides, hydantoins, oxazolidinediones, and glitazones, is a powerful way of directly accessing variety of biologically valuable chiral compounds. Herein, a bis(trichlorosilyl) nucleophilic intermediate formed from cyclic carboxyimides was reacted with aldehydes via (S)-SEGPHOS dioxide (SEGPHOSO), proceeding the aldol reaction in highly enantioselective fashion through a cyclic transition state. Furthermore, N-unprotected carboxyimides were chemoselectively activated, even in the presence of N-alkylated carboxyimides, to undergo stereoselective and chemoselective aldol reactions via in situ silicon tetrachloride activation. The functionalized cyclic carboxyimides is readily derived to the several synthetic units derivatization to various chiral building blocks without unnecessary protection/deprotection steps.

Investigation of tetrasubstituted heterocycles reveals hydantoins as a promising scaffold for development of novel antimicrobials with membranolytic properties

Mimics of antimicrobial peptides (AMPs) have been proposed as a promising class of antimicrobial agents. We report the analysis of five tetrasubstituted, cationic, amphipathic heterocycles as potential AMP mimics. The analysis showed that the heterocyclic scaffold had a strong influence on the haemolytic activity of the compounds, and the hydantoin scaffold was identified as a promising template for drug lead development. Subsequently, a total of 20 hydantoin derivatives were studied for their antimicrobial potency and haemolytic activity. We found 19 of these derivatives to have very low haemolytic toxicity and identified three lead structures, 2dA, 6cG, and 6dG with very promising broad-spectrum antimicrobial activity. Lead structure 6dG displayed minimum inhibitory concentration (MIC) values as low as 1 μg/mL against Gram-positive bacteria and 4-16 μg/mL against Gram-negative bacteria. Initial mode of action (MoA) studies performed on the amine derivative 6cG, utilizing a luciferase-based biosensor assay, suggested a strong membrane disrupting effect on the outer and inner membrane of Escherichia coli. Our findings show that the physical properties and structural arrangement induced by the heterocyclic scaffolds are important factors in the design of AMP mimics.

Rigidified Bis(sulfonyl)ethylenes as Effective Michael Acceptors for Asymmetric Catalysis: Application to the Enantioselective Synthesis of Quaternary Hydantoins

The catalytic, enantio- and diastereoselective addition of hydantoin surrogates II to "rigidified" vinylidene bis(sulfone) reagents is developed, thus overcoming the inability of commonly employed β-substituted vinylic sulfones to react. Adducts are transformed in enantioenriched 5,5-disubstituted hydantoins through hydrolysis and reductive desulfonylation processes providing new structures for eventual bioassays. Density functional theory studies that rationalize the observed reactivity and stereoselectivity trends are also provided.

Biologically Oriented Hybrids of Indole and Hydantoin Derivatives

Indoles and hydantoins are important heterocycles scaffolds which present in numerous bioactive compounds which possess various biological activities. Moreover, they are essential building blocks in organic synthesis, particularly for the preparation of important hybrid molecules. The series of hybrid compounds containing indoles and imidazolidin-2-one moiety with direct C-C bond were synthesized using an amidoalkylation one-pot reaction. All compounds were investigated as a growth regulator for germination, growth and development of wheat seeds (Triticum aestivum L). Their effect on drought resistance at very low concentrations (4 × 10^-5 M) was evaluated. The study highlighted identified the leading compounds, 3a and 3e, with higher growth-regulating activity than the indole-auxin analogues.

A new amino acid, hybrid peptides and BODIPY analogs: synthesis and evaluation of 2-aminotroponyl-L-alanine (ATA) derivatives

Natural aromatic α-amino acid residues play critical roles in the structural and functional organization of proteins owing to π-interactions. Their aromatic residues are derived from benzenoid scaffolds. Non-benzenoid aromatic scaffolds such as tropone and tropolone are also constituents of troponoid natural products. Tropolone has also the ability to exhibit π-interactions along with additional hydrogen bonding. Thus, amino acids comprising troponyl could be potential building blocks of novel peptidomimetics. This report describes the synthesis of the L-aminotroponylalanine amino acid (ATA) and its unusual activity with the peptide coupling agent EDC. Importantly, its di-peptides form β-sheet/-turn type secondary structures in organic solvents owing to the troponyl residue. This amino acid is an excellent scaffold for the synthesis of fluorescent amino acids such as BODIPY amino acid analogs. Nevertheless, this amino acid and its BODIPY derivatives can enter HeLa cells without exhibiting significant cytotoxicity at low concentrations (∼50 μM). Hence, ATA and its BODIPY derivatives are promising aromatic amino acids for the construction of potential peptidomimetics and fluorescent labelling of target peptides.

Light-empowered contra-thermodynamic stereochemical editing

Creating, conserving and modifying the stereochemistry of organic compounds has been the subject of significant research efforts in synthetic chemistry. Most synthetic routes are designed according to the stereoselectivity-determining step. Stereochemical editing is an alternative strategy, wherein the chiral-defining or geometry-defining steps are independent of the construction of the major scaffold or complexity. It enables late-stage alterations of stereochemistry and can generate isomers from a single compound. However, in many instances, stereochemical editing processes are contra-thermodynamic, meaning the transformation is unfavourable. To overcome this barrier, photocatalysis uses photogenerated radical species and introduces thermochemical biases. A range of synthetically valuable contra-thermodynamic stereochemical editing processes have been invented, including deracemization of chiral molecules, positional alkene isomerization and dynamic epimerization of sugars and diols. In this Review, we highlight the fundamental mechanisms of visible-light photocatalysis and the general reactivity modes of the photogenerated radical intermediates towards contra-thermodynamic stereochemical editing processes.

Multicomponent Reactions for the Synthesis of Active Pharmaceutical Ingredients

Multicomponent reactions 9i.e., those that engage three or more starting materials to form a product that contains significant fragments of all of them), have been widely employed in the construction of compound libraries, especially in the context of diversity-oriented synthesis. While relatively less exploited, their use in target-oriented synthesis offers significant advantages in terms of synthetic efficiency. This review provides a critical summary of the use of multicomponent reactions for the preparation of active pharmaceutical principles.

N-Alkyl Carbamoylimidazoles as Isocyanate Equivalents: Exploration of the Reaction Scope for the Synthesis of Ureas, Hydantoins, Carbamates, Thiocarbamates, and Oxazolidinones

The reaction of the HCl or trifluoroacetic acid salts of primary amines with carbonyldiimidazole (CDI) is shown to be a preparatively useful method for forming monosubstituted carbamoylimidazoles (28 examples) without the formation of symmetrical urea side products. The utility of these air- and water-stable crystalline carbamoylimidazole reagents was demonstrated by their reactions as blocked or masked isocyanate equivalents. Reaction with various classes of nucleophiles provides access to useful functional groups including ureas, carbamates, thiocarbamates, hydantoins, and oxazolidinones. A parallel synthesis library of 30 ureas was generated by the reaction of 6× carbamoylimidazole intermediates with 5× amines and triethylamine. The unsymmetrical urea-containing natural products macaurea A and pygmaniline A were also prepared in good yields (95% over four steps and 79% over three steps, respectively) using this approach. The reaction of carbamoylimidazoles with amino acid methyl esters followed by microwave irradiation in aqueous media gives hydantoins in high yields, further demonstrating the ability of carbamoylimidazoles as isocyanate surrogates. Three hydantoin-containing natural products including macahydantoin D and meyeniihydantoin A were prepared in nearly quantitative yields from proline methyl ester and carbamoylimidazoles. The reaction of carbamoylimidazoles with alcohols and thiols under basic conditions affords carbamates and thiocarbamates, respectively, in good yields. Lastly, a method for the preparation of chiral oxazolidinone heterocycles from chiral epoxy alcohols is demonstrated using a double displacement approach. The reactions occur with high regio- and stereoselectivity (dr ≥ 15:1 by ¹H NMR) via a domino attack of the corresponding alkoxides with carbamoylimidazoles followed by an intramolecular attack of the in situ generated urea anion at the proximal position of the epoxide group.

Prebiotic synthesis of α-amino acids and orotate from α-ketoacids potentiates transition to extant metabolic pathways

The Strecker reaction of aldehydes is the pre-eminent pathway to explain the prebiotic origins of α-amino acids. However, biology employs transamination of α-ketoacids to synthesize amino acids which are then transformed to nucleobases, implying an evolutionary switch-abiotically or biotically-of a prebiotic pathway involving the Strecker reaction into today's biosynthetic pathways. Here we show that α-ketoacids react with cyanide and ammonia sources to form the corresponding α-amino acids through the Bucherer-Bergs pathway. An efficient prebiotic transformation of oxaloacetate to aspartate via N-carbamoyl aspartate enables the simultaneous formation of dihydroorotate, paralleling the biochemical synthesis of orotate as the precursor to pyrimidine nucleobases. Glyoxylate forms both glycine and orotate and reacts with malonate and urea to form aspartate and dihydroorotate. These results, along with the previously demonstrated protometabolic analogues of the Krebs cycle, suggest that there can be a natural emergence of congruent forerunners of biological pathways with the potential for seamless transition from prebiotic chemistry to modern metabolism.

Trifluoromethylated Quinolone-Hydantoin Hybrids: Synthesis and Antibacterial Evaluation

A series of new trifluoromethyl-substituted quinolones and hydantoin hybrids has been synthesized and evaluated against Gram-positive bacterium (Staphylococcus aureus MTCC 96) and Gram-negative bacteria (Pseudomonas aeruginosa MTCC 441, Klebsiella pneumonia MTCC 109, and Escherichia coli MTCC 442). Compound  19c, having the 6-propene group on the quinolone ring, showed similar activity to a standard drug (chloramphenicol) by exhibiting MIC values of 50 µg/mL against S. aureus and P. aeruginosa. Physicochemical properties of compound 19c were also determined, which were in line with Lipinski’s rule of five, suggesting the suitability of compound 19c in biological systems. Various types of binding interactions of 19c within the active site of DNA gyrase of S. aureus were also streamlined by molecular docking studies, suggesting its capability to block the catalytic process of the DNA gyrase, which could be the possible reason for its antibacterial potential.

Synthesis of new 5-benzylidene-hydantoin esters

Compounds containing a hydantoin moiety are found in several medicines in clinical use. In this research, ethyl- and methyl-[2-(5-benzylidene)-2,4-dioxoimidazolidin-3-yl]acetyl esters are successfully synthesized over four reaction steps using conventional methods. The synthesis begins by subjecting hydantoin to a Knoevenagel condensation reaction with three different benzaldehydes to afford the penultimate products, which are further reacted with ethyl or methyl (bromoacetyl)alaninates, butanoates, valinates, and norvalinates to give the desired products as esters in low to moderate yields.

Enantioseparation of syn- and anti-3,5-Disubstituted Hydantoins by HPLC and SFC on Immobilized Polysaccharides-Based Chiral Stationary Phases

The enantioseparation of syn- and anti-3,5-disubstituted hydantoins 5a–i was investigated on three immobilized polysaccharide-based columns (CHIRAL ART Amylose-SA, CHIRAL ART Cellulose-SB, CHIRAL ART Cellulose-SC) by high performance liquid chromatography (HPLC) using n-hexane/2-PrOH (90/10, v/v) or 100% dimethyl carbonate (DMC) as mobile phases, respectively, and by supercritical fluid chromatography (SFC) using CO2/alcohol (MeOH, EtOH, 2-PrOH; 80/20, v/v) as a mobile phase. The chromatographic parameters, such as separation and resolution factors, have indicated that Amylose-SA is more suitable for enantioseparation of the most analyzed syn- and anti-3,5-disubstituted hydantoins than Celullose-SB and Cellulose-SC in both HPLC and SFC modalities. All three tested columns showed better enantiorecognition ability toward anti-hydantoins compared to syn-hydantoins, both in HPLC and SFC modes. We have demonstrated that environmentally friendly solvent DMC can be efficiently used as the mobile phase in HPLC mode for enantioseparation of hydantoins on the immobilized polysaccharide-based chiral stationary phases.

Molecular Rearrangement of Pyrazino[2,3-c]quinolin-5(6H)-ones during Their Reaction with Isocyanic Acid

New tetrahydropyrazino[2,3-c]quinolin-5(6H)-ones were prepared from 3-chloroquinoline-2,4(1H,3H)-diones and ethylene diamine. In their reaction with HNCO, an unprecedented molecular rearrangement produced new types of hydantoin derivatives. All prepared compounds were characterized on the basis of their ¹H, ¹³C, and ¹⁵N NMR and ESI mass spectra and some were authenticated by X-ray analysis of single crystalline material. A proposed mechanism for rearrangement is discussed in this essay. The CDK and ABL inhibition activity as well as in vitro cytotoxicity of the prepared compounds was also tested.

Synthesis and biological activity of novel hydantoin cyclohexyl sulfonamide derivatives as potential antimicrobial agents in agriculture

BACKGROUND

Plant disease is one of the most serious problems in agriculture that can damage crops. Chemical fungicides are widely used to control plant diseases, but have led to resistance and a series of environmental problems. It is, therefore, necessary to develop highly effective and eco-friendly antimicrobial compounds with novel structures.

RESULTS

A series of novel hydantoin cyclohexyl sulfonamide derivatives were synthesized through an intramolecular condensation reaction. The bioassay results indicated that a majority of the title compounds displayed potent inhibitory activity against Botrytis cinerea, Sclerotinia sclerotiorum and Erwinia carotorora. The in vivo inhibition rate of compound 3h was 91.01% against B. cinerea, which was higher than that of iprodione (84.07%). Compound 3w showed excellent antifungal activity against B. cinerea with a half-maximal effective concentration (EC₅₀ ) of 4.80 μg ml^-1 , which is lower than that of iprodione. Compound 3q had an EC₅₀ value of 1.44 μg ml^-1 against S. sclerotiorum, which was close to that of iprodione (1.39 μg ml^-1 ), and the inhibition rate was also similar to that of iprodione. Compounds 3i and 3w had the best inhibition efficacy against S. sclerotiorum, both on growth of the mycelium and sclerotia and in the greenhouse pot test in vitro. Further study showed that compounds 3h, 3r and 3s have superb antibacterial activity against E. carotorora with EC₅₀ values of 2.65, 4.24 and 4.29 μg ml^-1 respectively, and were superior to streptomycin sulfate (5.96 μg ml^-1 ).

CONCLUSION

Because of their excellent antifungal and antibacterial activity against B. cinerea, S. sclerotiorum and E. carotorora, these hydantoin cyclohexyl sulfonamide derivatives could be considered as suitable candidates for new antimicrobial agents. © 2021 Society of Chemical Industry.

[3+2]-Cycloaddition of azomethine ylides to 5-methylidene-3-aryl-2-сhalcogen-imidazolones: access to dispiro indolinone-pyrrolidine-imidazolones

A synthesis of dispiro derivatives from 5-methylidene-2-chalcogenimidazolones and azomethine ylides generated from isatins and N-substituted α-amino acids has been developed.

Copper coordination compounds with (5Z,5Z')-2,2'-(alkane-α,ω-diyldiselenyl)-bis-5-(2-pyridylmethylene)-3,5-dihydro-4H-imidazol-4-ones. Comparison with sulfur analogue

A series of new organic ligands (5Z,5Z')-2,2'-(alkane-α,ω-diyldiselenyl)-bis-5-(2-pyridylmethylene)-3,5-dihydro-4H-imidazol-4-ones (L) consisting of two 5-(2-pyridylmethylene)-3,5-dihydro-4H-imidazol-4-one units linked with polymethylene chains of various lengths (n = 2-10, where n is the number of CH₂ units) have been synthesized. The reactions of these ligands with CuCl₂·2H₂O and CuClO₄·6H₂O gave Cu²⁺ or Cu¹⁺ containing mono- and binuclear complexes with Cu₂LCl _x (x = 2-4) or CuL(ClO₄) _y (y = 1, 2) composition. It was shown that the agents reducing Cu²⁺ to Cu¹⁺ in the course of complex formation can be both a ligand and an organic solvent in which the reaction is carried out. This fundamentally distinguishes the selenium-containing ligands L from their previously described sulfur analogs, which by themselves are not capable of reducing Cu²⁺ during complexation under the same conditions. A higher cytotoxicity and reasonable selectivity to cancer cell lines for synthesized complexes of selenium-containing ligands was shown; unlike sulfur analogs, ligands L themselves demonstrate a high cytotoxicity, comparable in some cases to the toxicity of copper-containing complexes.

Phase-Transfer-Catalyzed Alkylation of Hydantoins

A highly efficient, cost-effective, and environmentally friendly protocol is reported for the C5-selective alkylation of hydantoins under phase-transfer catalysis. The reactions are scalable and only require a catalytic amount of tetrabutylammonium bromide (TBAB) to achieve high yields under mild reaction conditions. Moreover, the method is applicable to a wide range of electrophiles, including alkyl-, allyl-, propargyl-, and benzyl halides, as well as acrylates and dibromoalkanes, but also to virtually any hydantoin precursor. We also highlight the potential for an enantioselective adaptation using a chiral phase-transfer catalyst.

Mechanochemical Preparation of Protein : hydantoin Hybrids and Their Release Properties

Mechanochemistry is a versatile methodology that can be employed both for covalent bond formation in organic synthesis as well as a mediator to allow preparation novel colloidal dispersions for drug delivery. Herein, ball-milling was employed for the solid-state preparation of fluorescent hydrophobic hydantoins, followed by the unprecedented mechanochemically-mediated complexation of hydrophobic hydantoins within hydrophilic protein β-lactoglobulin (BLG) and BLG nanofibrils (BLGNFs). These hydantoin:protein materials were in turn incorporated into hydrogels. The effect of incorporation of hydantoins into proteins, as well as the effect of protein structure, on the release properties were then investigated. The conversion of BLG to BLGNFs led to a more sustained release demonstrating that heat treatment of BLG into BLGNFs could be employed to modify release properties. To the best of our knowledge, this is the first example where protein : hydantoin complexes were prepared by mechanochemical methodology and mechanochemistry was combined with self-assembly in order to prepare protein nanomaterials for drug-delivery applications. In addition, the use of the developed protein materials is not limited to delivery of drugs but can for example be employed as components of smart food (delivery of nutrients) or release systems of pesticides.