RECENT DEVELOPMENTS IN HYDANTOIN CHEMISTRY. A REVIEW

Regioselective Synthesis of α-Quaternary Amino Acid Derivatives Enabled by Photoinduced Energy Transfer

α-Quaternary amino acids have found application in many biologically relevant compounds and pharmaceuticals. Although there are many methods for the synthesis of α-quaternary amino acids, most of them are mainly realized with the aid of transition metals and complex ligands. We present herein a 2,7-Br-4CzIPN catalyzed regioselective alkylation of azlactones with redox-active esters via radical-radical couplings. Strikingly, this approach is devoid of any metal or additive and shows broad scope and superior sensitive functional group compatibility.

Difluorocarbene-induced [1,2]- and [2,3]-Stevens rearrangement of tertiary amines

The [1,2]- and [2,3]-Stevens rearrangements are one of the most fascinating chemical bond reorganization strategies in organic chemistry, and they have been demonstrated in a wide range of applications, representing a fundamental reaction tactic for the synthesis of nitrogen compounds in chemical community. However, their applicabilities are limited by the scarcity of efficient, general, and straightforward methods for generating ammonium ylides. Herein, we report a general difluorocarbene-induced tertiary amine-involved [1,2]- and [2,3]-Stevens rearrangements stemmed from in situ generated difluoromethyl ammonium ylides, which allows for the rearrangements of versatile tertiary amines bearing either allyl, benzyl, or propargyl groups, resulting in the corresponding products in one reaction under the same reaction conditions with a general way. Broad substrate scope, simple operation, mild reaction conditions and late-stage modification of natural products highlight the advantages of this strategy, meanwhile, this general rearrangement reaction is believed to bring opportunities for the transformations of nitrogen ylides and the assembly of valuable tertiary amines and amino acids. This will further enrich the reaction repertoire of difluorocarbene species, facilitate the development of reactions involving difluoromethyl ammonium salts, and provide an avenue for the development of this type of rearrangement reactions.

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.

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.

Metalloradical approach for concurrent control in intermolecular radical allylic C-H amination

Although they offer great potentials, the high reactivity and diverse pathways of radical chemistry pose difficult problems for applications in organic synthesis. In addition to the differentiation of multiple competing pathways, the control of various selectivities in radical reactions presents both formidable challenges and great opportunities. To regulate chemoselectivity and regioselectivity, as well as diastereoselectivity and enantioselectivity, calls for the formulation of conceptually new approaches and fundamentally different governing principles. Here we show that Co(II)-based metalloradical catalysis enables the radical chemoselective intermolecular amination of allylic C-H bonds through the employment of modularly designed D2-symmetric chiral amidoporphyrins with a tunable pocket-like environment as the supporting ligand. The reaction exhibits a remarkable convergence of regioselectivity, diastereoselectivity and enantioselectivity in a single catalytic operation. In addition to demonstrating the unique opportunities of metalloradical catalysis in controlling homolytic radical reactions, the Co(II)-catalysed convergent C-H amination offers a route to synthesize valuable chiral α-tertiary amines directly from an isomeric mixture of alkenes.

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.

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.

15,15-Diphenyl-2,3,4,5,6,8,9,11,12-octa-hydro-imidazo[2,1-h][1,4,12]trioxa[7]thia-[9]azacyclo-tetra-decin-14(15H)-one

The title mol-ecule, C₂₃H₂₆N₂O₄S, adopts a cup-shaped conformation. In the crystal, layers lying parallel to the ab plane are formed by C-H⋯O hydrogen bonds and C-H⋯π(ring) inter-actions. The layers stack along the c-axis direction through normal van der Waals inter-actions.

Sulfonamides with Heterocyclic Periphery as Antiviral Agents

Sulfonamides are the basic motifs for a whole generation of drugs from a large group of antibiotics. Currently, research in the field of the new sulfonamide synthesis has received a "second wind", due to the increase in the synthetic capabilities of organic chemistry and the study of their medical and biological properties of a wide spectrum of biological activity. New reagents and new reactions make it possible to significantly increase the number of compounds with a sulfonamide fragment in combination with other important pharmacophore groups, such as, for example, a wide class of N-containing heterocycles. The result of these synthetic possibilities is the extension of the activity spectrum-along with antibacterial activity, many of them exhibit other types of biological activity. Antiviral activity is also observed in a wide range of sulfonamide derivatives. This review provides examples of the synthesis of sulfonamide compounds with antiviral properties that can be used to develop drugs against coxsackievirus B, enteroviruses, encephalomyocarditis viruses, adenoviruses, human parainfluenza viruses, Ebola virus, Marburg virus, SARS-CoV-2, HIV and others. Since over the past three years, viral infections have become a special problem for public health throughout the world, the development of new broad-spectrum antiviral drugs is an extremely important task for synthetic organic and medicinal chemistry. Sulfonamides can be both sources of nitrogen for building a nitrogen-containing heterocyclic core and the side chain substituents of a biologically active substance. The formation of the sulfonamide group is often achieved by the reaction of the N-nucleophilic center in the substrate molecule with the corresponding sulfonylchloride. Another approach involves the use of sulfonamides as the reagents for building a nitrogen-containing framework.

Modular Synthesis of α,α-Diaryl α-Amino Esters via Bi(V)-Mediated Arylation/SN2-Displacement of Kukhtin–Ramirez Intermediates

We report a concise and modular approach to α,α-diaryl α-amino esters from readily available α-keto esters. This mild, one-pot protocol proceeds via ketone umpolung, with in situ formation of a Kukhtin–Ramirez intermediate preceding sequential electrophilic arylation by Bi(V) and S_N2 displacement by an amine. The methodology is compatible with a wide range of anilines and primary amines - including derivatives of drugs and proteinogenic amino acids - Bi(V) arylating agents, and α-keto ester substrates.

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.

Synthesis of Unnatural α-Amino Acid Derivatives via Photoredox Activation of Inert C(sp3)-H Bonds

The synthesis of unnatural, tertiary amino acids is a challenging task. While decarboxylation-radical addition has been an important strategy for their formation, the use of alkyl radicals from C(sp³)-H bonds has not been fully explored. Herein, we report a photocatalytic protocol for the synthesis of unnatural α-amino esters employing abundant alkanes and imines retaining full atom economy. When this method is applied, several amino acid derivatives are synthesized in moderate to good yields.

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.

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.

Pd-Catalysed oxidative carbonylation of α-amino amides to hydantoins under mild conditions

The first example of palladium-catalysed oxidative carbonylation of unprotected α-amino amides to hydantoins is described here. The selective synthesis of the target compounds was achieved under mild conditions (1 atm of CO), without ligands and bases. The catalytic system overrode the common reaction pathway that usually leads instead to the formation of symmetrical ureas.

Direct N1-Selective Alkylation of Hydantoins Using Potassium Bases

Hydantoins, including the antiepileptic drug phenytoin, contain an amide nitrogen and an imide nitrogen, both of which can be alkylated. However, due to the higher acidity of its proton, N³ can be more easily alkylated than N¹ under basic conditions. In this study, we explored methods for direct N¹-selective methylation of phenytoin and found that conditions using potassium bases [potassium tert-butoxide (^tBuOK) and potassium hexamethyldisilazide (KHMDS)] in tetrahydrofuran (THF) gave N¹-monomethylated phenytoin in good yield. The applicable scope of this reaction system was found to include various hydantoins and alkyl halides. To explore the function of methylated hydantoins, the effects of a series of methylated phenytoins on P-glycoprotein were examined, but none of methylated products showed inhibitory activity toward rhodamine 123 efflux by P-glycoprotein.

Enantioselective Synthesis of Chiral Substituted 2,4-Diketoimidazolidines and 2,5-Diketopiperazines via Asymmetric Hydrogenation

An enantioselective hydrogenation of 5-alkylidene-2,4-diketoimidazolidines (hydantoins) and 3-alkylidene-2,5-ketopiperazines catalyzed by the Rh/f-spiroPhos complex under mild conditions has been developed, which provides an efficient approach to the highly enantioselective synthesis of chiral hydantoins and 2,5-ketopiperazine derivatives with high enantioselectivities up to 99.9% ee.

The Bucherer-Bergs Multicomponent Synthesis of Hydantoins-Excellence in Simplicity

Hydantoins and their hybrids with other molecules represent a very important group of heterocycles because they exhibit diverse biological and pharmacological activities in medicinal and agrochemical applications. They also serve as key precursors in the chemical or enzymatic synthesis of significant nonnatural α-amino acids and their conjugates with medical potential. This review provides a comprehensive treatment of the synthesis of hydantoins via the Bucherer-Bergs reaction including the Hoyer modification but limited to free carbonyl compounds or carbonyl compounds protected as acetals (ketals) and cyanohydrins used as starting reaction components. In this respect, the Bucherer-Bergs reaction provides an efficient and simple method in the synthesis of important natural products as well as for the preparation of new organic compounds applicable as potential therapeutics. The scope and limitations, as well as a comparison with some other methods for preparing hydantoins, are also discussed.

Design, synthesis, structural and molecular characterization, toxicity, psychotropic activity and molecular docking evaluation of a novel phenytoin derivative: 3-decyl-5,5-diphenylimidazolidine-2,4-dione

The hydantoin scaffold is of substantial importance and it is commonly used in drug discovery. Herein, we report the synthesis of a novel phenytoine (a hydantoin derivative) with high yield by the reaction of phenytoin with 1-bromodecyl agent. Namely, 3-decyl-5,5- diphenylimidazolidine-2,4-dione (3DDID). The optimized geometry of the compound was calculated using density functional theory (DFT) method by B3LYP with 6-311++G(d,p) basis set. For this calculation, the X-ray data were used as initial values. Molecular electrostatic potential (MEP) surface and Frontier molecular orbitals (FOMs) were prepared for the compound. The crystal structure of the title compound contains intermolecular N-H···O, C-H···O hydrogen bonds and weak C-H···π interactions. Hirshfeld surface analysis and 2D fingerprint plots of the molecule aid comparison of intermolecular interactions and these analysis reveals that two close contacts are associated with intermolecular hydrogen bonds. The psychotropic activity evaluation of the synthesized compound was further explored using hole bored test for exploratory behaviors, dark//light box test for anxiolytic activity and Rota-road, traction, chimney testes were used to assess the myrelaxant effect. In addition, molecular modeling study was also conducted to rationalize the potential as neurotherapeutic drugs of our synthesized compound by predicting their binding modes, binding affinities and optimal orientation at the active site of the GABA-A receptor and Na⁺ channel. Finally, in silico ADMET predictions was also examined. HighlightsSynthesis, structural, and molecular characterization of a novel phenytoin derivative.DFT, XRD, and the Hirshfeld surface analysis of crystal structure was studied.Acute toxicity and psychotropic activity evaluation of 3-decyl-5,5 diphenylimidazolidine-2,4-dione (3DDID).Molecular modeling studies have been conducted to rationalize the obtained data and to determine the probable binding mode.Communicated by Ramaswamy H. Sarma.

Designed Synthesis of Diversely Substituted Hydantoins and Hydantoin-Based Hybrid Molecules: A Personal Account

Hydantoin and its analogues such as thiohydantoin and iminohydantoin have received substantial attention from both a chemical and a biological point of view. Several compounds of this class have shown useful pharmacological activities such as anticonvulsant, antitumor, antiarrhythmic, and herbicidal properties that have led, in some cases, to clinical applications. Because of these broad-spectrum activities, intensive research efforts have been dedicated in industry and academia to the synthesis and structural modifications of hydantoin and its derivatives. Realizing the importance of hydantoin in organic and medicinal chemistry, we also initiated a research program that successfully designed and developed new routes and methods for the formation of hydantoin, thiohydantoin, and iminohydantoin substituted at various positions, particularly at the N-1 position without following a protection–deprotection strategy. Because combinations of two or more pharmacophoric groups can lead to hybrid molecules that display a mixed mechanism of action on biological targets, we extended our developed strategy to the syntheses of new types of hydantoin-based hybrid molecules by combining hydantoin with a triazole, isoxazoline, or phosphate scaffold as a second pharmacophore to exploit their diverse biological functions.

1 Introduction

2 Chemistry and Properties

2.1 Physical Properties

2.2 Chemical Properties

2.3 Biological Properties

3 General Synthetic Methods

4 Synthesis of Diversely Substituted Hydantoins

5 Synthesis of Diversely Substituted Thiohydantoins

6 Synthesis of Diversely Substituted Iminohydantoins

7 Fused or Bicyclic (Thio)hydantoins

8 Di- or Multivalent (Thio)hydantoins

9 Hydantoin-Based Hybrid Molecules

9.1 Hydantoin–Isooxazoline Hybrids

9.2 Hydantoin–Triazole Hybrids

9.3 Hydantoin–Phosphate Hybrids: Phosphorylated Hydantoins

10 Summary and Outlook

Hydantoin-bridged medium ring scaffolds by migratory insertion of urea-tethered nitrile anions into aromatic C-N bonds

Bicyclic or tricyclic nitrogen-containing heterocyclic scaffolds were constructed rapidly by intramolecular nucleophilic aromatic substitution of metallated nitriles tethered by a urea linkage to a series of electronically unactivated heterocyclic precursors. The substitution reaction constitutes a ring expansion, enabled by the conformationally constrained tether between the nitrile and the heterocycle. Attack of the metallated urea leaving group on the nitrile generates a hydantoin that bridges the polycyclic products. X-ray crystallography reveals ring-dependant strain within the hydantoin.

Synthesis and crystal structure of 3-octyl-5,5-diphenylimidazolidine-2,4-dione, C23H28N2O2

C23H28N2O2, orthorhombic, Pbca (no. 61), a = 10.713(2) Å, b = 15.689(3) Å, c = 24.485(5) Å, V = 4115.2(14) Å3, Z = 8, Rgt(F) = 0.0581, wRref(F2) = 0.1734, T = 120(2) K.

Unconventional Secondary Structure Mimics: Ladder-Rungs

Secondary structures tend to be recognizable because they have repeating structural motifs, but mimicry of these does not have to follow such well-defined patterns. Bioinformatics studies to match side-chain orientations of a novel hydantoin triazole chemotype (1) to protein-protein interfaces revealed it tends to align well across parallel and antiparallel sheets, like rungs on a ladder. One set of these overlays was observed for the protein-protein interaction uPA⋅uPAR. Consequently, chemotype 1 was made with appropriate side-chains to mimic uPA at this interface. Biophysical assays indicate these compounds did in fact bind uPAR, and elicit cellular responses that affected invasion, migration, and wound healing.

Cu-catalyzed N-3-Arylation of Hydantoins Using Diaryliodonium Salts

A general Cu-catalyzed, regioselective method for the N-3-arylation of hydantoins is described. The protocol utilizes aryl(trimethoxyphenyl)iodonium tosylate as the arylating agent in the presence of triethylamine and a catalytic amount of a simple Cu-salt. The method is compatible with structurally diverse hydantoins and operates well with neutral aryl groups or aryl groups bearing weakly donating/withdrawing elements. It is also applicable for the rapid diversification of pharmaceutically relevant hydantoins.

Experimental and DFT study of the effect of mercaptosuccinic acid on cyanide-free immersion gold deposition

In order to search for an effective alternative to cyanide for gold plating, mercaptosuccinic acid (MSA) was selected as the complexing agent of Au⁺ by open circuit potential tests and gold plating compared with 1-hydroxyethylidene-1,1-diphosphonic acid and aminomethylphosphonic acid. For the first time, a novel, stable, slightly acidic and cyanide-free gold plating bath was prepared. Scanning electron microscopy, Tafel tests, and tin dipping tests showed that the Cu/Ni–P/Au coating had a fine and even grain size, no black pad, good corrosion resistance, and good weldability. Quantum chemical calculations based on density functional theory were used to further study complexants and complexes. Molecular electrostatic potential indicates that Au⁺ approaches MSA in the direction of C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O. Frontier molecular orbital theory, atomic contribution to orbital composition, condensed local softness, and average local ionization energy indicate that the coordination capacity of the S atom in MSA is much stronger than that of other atoms. Fuzzy bond order analysis shows that the S–Au–S coordination structure is the most stable form in the plating solution. UV-visible absorption spectroscopy clarifies that the wavelength is redshifted when MSA–Au(i) ions form.

A cyanide-free gold plating bath was prepared and the complexing capacity of mercaptosuccinic acid with Au(i) was studied through density functional theory.