The multicomponent reactions and their libraries for natural and preparative chemistry

Picolinamide-assisted ortho-C-H functionalization of pyrenylglycine derivatives using aryl iodides

Chemical transformations involving the pyrenylglycine motif (an unnatural amino acid) and practical methods toward it are seldom known. This work aimed at developing a method for synthesizing novel pyrenylglycine (pyrene-based glycine) unnatural amino acid derivatives. To realize this, initially, a new pyrenylglycine substrate possessing the picolinamide moiety was assembled via the Ugi multicomponent reaction. The picolinamide moiety linked to amine substrates is a well-known bidentate directing group for accomplishing the site-selective γ-C-H functionalization of amines. Subsequently, it was aimed at using a Pd(II)-catalyzed bidentate directing group-aided γ-C-H arylation strategy for generating a wide range of unprecedented examples of C(2)-H arylated pyrenylglycines. Accordingly, pyrenylglycine possessing the picolinamide moiety was subjected to Pd(II)-catalyzed C(2)-H arylation in the non-K-region to afford a library of C(2)-arylated pyrenylglycines (π-extended pyrenes). Additionally, pyrenylglycine-based small peptides were assembled using C(2)-arylated pyrenylglycines. The X-ray structure of a representative compound was obtained, which corroborated the structure of pyrenylglycine and the regioselectivity of C(2)-H arylation of the pyrene in the non-K-region.

Isocyanide-based Multicomponent Reactions (IMCRs) in Water or Aqueous Biphasic Systems

BACKGROUND

Isocyanide is an intriguing one-carbon synthon that is frequently employed in a variety of carbon-carbon and carbon-heteroatom bond-forming reactions. Isocyanide-based multicomponent reactions (IMCRs) are effective synthetic tools in organic synthesis for the preparation of complex heterocyclic molecules. The IMCRs in water have become an attractive research direction, enabling simultaneous growth of both IMCRs and green solvents towards ideal organic synthesis.

OBJECTIVE

The goal of this review is to provide a general overview of IMCRs in water or biphasic aqueous systems for accessing various organic molecules, as well as an examination of their benefits and mechanistic insights.

CONCLUSION

High atom economies, mild reaction conditions, high yields, and catalyst-free processes are crucial features of these IMCRs in water or biphasic aqueous systems.

Multicomponent Assembly of Bicyclic Aza-peroxides Catalyzed by Samarium Complexes and Their Cytotoxic Activity

An original strategy toward bridged tetraoxazaspirobicycloalkanes was developed. The synthesis is based on a three-component condensation-cyclization reaction of primary arylamines with 1,1'-peroxybis (1-hydroperoxycycloalkanes) and pentane-1,5-dial catalyzed by Sm(NO3)3·6H2O. The structures and conformations of the products were determined by X-ray diffraction analysis and 1H and 13C NMR spectroscopy. High cytotoxic activity and biological potential toward ferroptosis induction were found for the synthesized bicyclic aza-peroxides.

One-Pot Multicomponent Polymerization, Metal-, and Non-Metal-Catalyzed Synthesis of Organoselenium Compounds

The one-pot multicomponent synthetic strategy of organoselenium compounds represents an alternative and robust protocol to the conventional multistep methods. During the last decade, a potential advance has been made in this domain. This review discusses the latest advances in the polymerization, metal, and metal-free one-pot multicomponent synthesis of organoselenium compounds.

Ugi Reaction Mediated Detergent Assembly for Membrane Protein Studies

Despite the continuous efforts, the current repertoire of detergents is still far from sufficient for the biophysics studies of membrane proteins (MPs). Toward the rapid expansion of detergent diversity, we herein report a new strategy based on Ugi reaction mediated modular assembly. Structural varieties, including hydrophobic tails and hydrophilic heads, could be conveniently introduced from the multiple reaction components. New detergents then were comprehensively evaluated in the physical properties and preliminarily screened by the thermal stabilization for a transporter MsbA and a spectrum of G protein-coupled receptors (GPCRs). For the glucagon-like peptide-1 receptor (GLP-1R), a class B GPCR, detergent M-23-M finally stood out in a second evaluation for the maintenance of homogeneity and was further illustrated its application in the improvement of NMR study. Besides the promising utility in the MP study, the current results exhibit intriguing structural-physical relationship that would allow the guidance in the tuning of detergent properties in the future.

Catalytic Approaches to Multicomponent Reactions: A Critical Review and Perspectives on the Roles of Catalysis

In this review, we comprehensively describe catalyzed multicomponent reactions (MCRs) and the multiple roles of catalysis combined with key parameters to perform these transformations. Besides improving yields and shortening reaction times, catalysis is vital to achieving greener protocols and to furthering the MCR field of research. Considering that MCRs typically have two or more possible reaction pathways to explain the transformation, catalysis is essential for selecting a reaction route and avoiding byproduct formation. Key parameters, such as temperature, catalyst amounts and reagent quantities, were analyzed. Solvent effects, which are likely the most neglected topic in MCRs, as well as their combined roles with catalysis, are critically discussed. Stereocontrolled MCRs, rarely observed without the presence of a catalytic system, are also presented and discussed in this review. Perspectives on the use of catalytic systems for improved and greener MCRs are finally presented.

High-component reactions (HCRs): An overview of MCRs containing seven or more components as versatile tools in organic synthesis

Recently, multi-component reactions (MCRs) have gained special attention due to their versatility for the synthesis of polycyclic heterocycles. Moreover, their applicability can become more widespread as they can be combined together as a union of MCRs. In this overview, the authors have tried to collect the MCRs containing more than seven components that can lead to effectual heterocycles in organic and/or pharmaceutical chemistry. The review contains papers published up to the end of 2020. The subject is classified based on the number of substrates, such as seven-, eight-, nine-, ten-, and more components. The authors expect their report to be helpful for researchers to clarify their route to significant MCRs.

Enhancing the chemosensitivity of HepG2 cells towards cisplatin by organoselenium pseudopeptides

Despite all recent advances in the treatment of hepatocellular carcinoma (HCC), chemotherapy resistance still represents a major challenge in its successful clinical management. Chemo-sensitization offers an attractive strategy to counter drug resistance. Herein we report the identification of novel organoselenium-based pseudopeptides as promising highly effective chemo-sensitizers in treating HCC with cisplatin. A series of functionalized pseudopeptide- (5-9 and 17-19), peptidomimetic- (10-12 and 20-23), and tetrazole-based (13-16 and 24-27) organoselenium compounds were synthesized via isonitrile-based multicomponent reactions from two novel selenium-containing isocyanides. All compounds were evaluated for their cytotoxicity against HepG2 and the non-cytotoxic doses were used to restor the sensitivity of the cells to cisplatin. New organoselenium compounds (7, 9, 15, or 23) led to an effective chemo-sensitization of HepG2 cells towards cisplatin (up-to 27-fold). Cell cycle studies indicate that the most potent peptidomimetic diselenide 23 arrested cells at the S phase and induced apoptosis via ROS modulation.

How and Why to Investigate Multicomponent Reactions Mechanisms? A Critical Review

We review the most innovative efforts and greatest challenges faced when elucidating multicomponent reactions (MCRs) mechanisms. When compared to traditional reactions, the often two or more concurrent reactions pathways and the greater number of possible intermediates in MCRs turn their mechanistic investigation both a harder and trickier task. The common approaches used to investigate reaction mechanisms are often unable to clarify MCRs mechanisms; hence few but clever approaches are currently used to determine these mechanisms and to depict their key transformations. Their complexity has required most innovative approaches and the use of a number of unique techniques that have shed light over the favored pathway selected from the myriad of alternatives theoretically available for MCRs. This review focuses on the most successful efforts applied by a few leading groups to perform these puzzlingly investigations.

α-Amidoamids as New Replacements of Antibiotics-Research on the Chosen K12, R2-R4 E. coli Strains

A preliminary study of α-amidoamids as new potential antimicrobial drugs was performed. Special emphasis was placed on selection of structure of α-amidoamids with the highest biological activity against different types of Gram-stained bacteria by lipopolysaccharide (LPS). Herein, Escherichia coli model strains K12 (without LPS in its structure) and R1-R4 (with different length LPS in its structure) were used. The presented work showed that the antibacterial activity of α-amidoamids depends on their structure and affects the LPS of bacteria. Moreover, the influence of various newly synthesized α-amidoamids on bacteria possessing smooth and rought LPS and oxidative damage of plasmid DNA caused by all newly obtained compounds was indicated. The presented studies clearly explain that α-amidoamids can be used as substitutes for antibiotics. The chemical and biological activity of the analysed α-amidoamids was associated with short alkyl chain and different isocyanides molecules in their structure such as: tetr-butyl isocyanide or 2,5-dimethoxybenzyl isocyanide. The observed results are especially important in the case of the increasing resistance of bacteria to various drugs and antibiotics.

Phenothiazine and amide-ornamented dihydropyridinesviaa molecular hybridization approach: design, synthesis, biological evaluation and molecular docking studies

A series of novel phenothiazinyldihydropyridine dicarboxamides7a–7jwas synthesized by adopting a multi-step synthetic strategy and characterized through physical and spectral techniques.

Mechanistic knowledge and noncovalent interactions as the key features for enantioselective catalysed multicomponent reactions: a critical review

This critical short review focuses on some key features which determine successful enantioselective catalysed multicomponent reactions (MCRs) and are typically underappreciated in the literature.

On the direct use of CO2 in multicomponent reactions: introducing the Passerini four component reaction

We introduce a novel isocyanide-based multicomponent reaction, the Passerini four component reaction (P-4CR), by replacing the carboxylic acid component of a conventional Passerini three component reaction (P-3CR) with an alcohol and CO₂. Key to this approach is the use of a switchable solvent system, allowing the synthesis of a variety of α-carbonate-amides. The reaction was first investigated and optimized using butanol, isobutyraldehyde, tert-butyl isocyanide and CO₂. Parameters investigated included the effect of reactant equivalents, reactant concentration, solvent, catalyst, catalyst concentration and CO₂ pressure. Of the other parameters, the purity of the aldehyde and its tendency to oxidize was one of the most critical parameters for a successful P-4CR. After optimization, a total of twelve (12) P-4CR compounds were synthesized with conversions ranging between 16 and 82% and isolated yields between 18 and 43%. Their structures were confirmed via¹H and ¹³C NMR, FT-IR and high resolution mass spectrometry (ESI-MS). In addition, three (3) hydrolysis products of P-4CR (α-hydroxyl-amides) were successfully isolated with yields between 23 and 63% and fully characterized (¹H, ¹³C NMR, FT-IR and ESI-MS) as well.

We introduce a novel isocyanide-based multicomponent reaction, the Passerini four component reaction (P-4CR), by replacing the carboxylic acid component of a conventional Passerini three component reaction (P-3CR) with an alcohol and CO₂.

Concise Synthesis of Macrocycles by Multicomponent Reactions

A short reaction pathway was devised to synthesize a library of artificial 18-27-membered macrocycles. The five-step reaction sequence involves ring opening of a cyclic anhydride with a diamine, esterification, coupling with an amino acid isocyanide, saponification, and, finally, macro-ring closure using an Ugi or, alternatively, a Passerini multicomponent reaction. Three out of the five steps allow for the versatile introduction of linker elements, side chains, and substituents with aromatic, heteroaromatic, and aliphatic character. The versatile pathway is described for 15 different target macrocycles on a mmol scale. Artificial macrocycles have recently become of great interest due to their potential to bind to difficult post-genomic targets.

Ring Rearrangement Metathesis in 7-Oxabicyclo[2.2.1]heptene (7-Oxanorbornene) Derivatives. Some Applications in Natural Product Chemistry

Metathesis reactions is firmly established as a valuable synthetic tool in organic chemistry, clearly comparable with the venerable Diels-Alder and Wittig reactions and, more recently, with the metal-catalyzed cross-coupling reactions. Metathesis reactions can be considered as a fascinating synthetic methodology, allowing different variants regarding substrate (alkene and alkyne metathesis) and type of metathetical reactions. On the other hand, tandem metathesis reactions such Ring Rearrangement Metathesis (RRM) and the coupling of metathesis reaction with other reactions of alkenes such as Diels-Alder or Heck reactions, makes metathesis one of the most powerful and reliable synthetic procedure.

In particular, Ring-Rearrangement Metathesis (RRM) refers to the combination of several metathesis transformations into a domino process such as ring-opening metathesis (ROM)/ring-closing metathesis (RCM) and ROM-cross metathesis (CM) in a one-pot operation. RRM delivers complex frameworks that are difficult to assemble by conventional methods constitutingan atom economic process. RRM is applicable to mono- and polycyclic systems of varying ring sizes such as cyclopropene, cyclobutene, cyclopentene, cyclohexene, pyran systems, bicyclo[2.2.1]heptene derivatives, bicyclo[2.2.2]octene derivatives, bicyclo[3.2.1]octene derivatives and bicyclo[3.2.1]octene derivatives.

In this review our attention has focused on the RRM reactions in 7-oxabicyclo[2.2.1]heptene derivatives and on their application in the synthesis of natural products or significant subunits of them.

An expedient sequential one-pot four component synthesis of novel steroidal spiro-pyrrolidine heterocycles in ionic liquid

A facile one-pot synthesis of novel steroidal dispiro-indenoquinoxaline pyrrolidines via multicomponent-[3+2]-cycloaddition of azomethine ylides in ionic liquid is described. The structure of cycloadduct is confirmed by IR, (1)H NMR, (13)C NMR, high resolution mass spectroscopy and elemental analysis.

Dynamic ¹H NMR studies of hindered internal rotations in the synthesized particular phosphorus ylide: experimental and theoretical approaches

Dynamic (1)H NMR measurements were performed within the synthesized particular phosphorus ylide involving 4-formylphenyl phenylcarbamate. Four rotational process and thereby parameters were targeted for rotation around the CC, C-C, HCNC and OCNC bonds. The Gibbs free activation energy in CDCl3, ΔG(≠)exp, was found to be 64 ± 2, 50 ± 2, 41 ± 2 and 63 ± 2, respectively. These findings were compared with related ab initio and DFT results on simulated situation. Theoretical methods tested, were comparable to the present D (1)H NMR data.

MCR synthesis of a tetracyclic tetrazole scaffold

Scaffold diversity is key in the ongoing exercise of discovery of novel bioactive compounds using high throughput screening (HTS). Based on the Ugi tetrazole synthesis we have designed novel bi- and tri-cyclic scaffolds featuring interesting pharmacophore properties. The compounds of the scaffold (B) are synthesizable in large diversity and numbers in two steps using (hetero)phenylethylamines, HN3, oxo components and iscyanoacetaldehyde(dimethylacetale). The chemistry is amenable to parallel synthesis and is used to enhance and fill the screening decks of the European Lead factory (ELF). Here, we are reporting full experimental details, scope and limitations of the reaction, cheminformatic analysis and the 3D structures of selected compounds.

Toward lead-oriented synthesis: one-pot version of Castagnoli condensation with nonactivated alicyclic anhydrides

One-pot variation of Castagnoli condensation, that is, reaction of cyclic anhydrides, amines, and aldehydes, has been developed as a combinatorial approach to 1,2-disubstituted 5-oxopyrrolidine- and 6-oxopiperidine-3-carboxylic acids, as well as their benzo-analogues. Utility of the method to multigram preparation of building blocks and synthetic intermediates was also demonstrated. The final products are obtained in high yields and diastereoselectivity. The method fits well in the concept of lead-oriented synthesis; in particular, it can be used for the design of lead-like compound libraries, even if the strictest cut-offs are applied to the physicochemical properties of their members.

Using remote substituents to control solution structure and anion binding in lanthanide complexes

A study of the anion-binding properties of three structurally related lanthanide complexes, which all contain chemically identical anion-binding motifs, has revealed dramatic differences in their anion affinity. These arise as a consequence of changes in the substitution pattern on the periphery of the molecule, at a substantial distance from the binding pocket. Herein, we explore these remote substituent effects and explain the observed behaviour through discussion of the way in which remote substituents can influence and control the global structure of a molecule through their demands upon conformational space. Peripheral modifications to a binuclear lanthanide motif derived from α,α'-bis(DO3 Ayl)-m-xylene are shown to result in dramatic changes to the binding constant for isophthalate. In this system, the parent compound displays considerable conformational flexibility, yet can be assumed to bind to isophthalate through a well-defined conformer. Addition of steric bulk remote from the binding site restricts conformational mobility, giving rise to an increase in binding constant on entropic grounds as long as the ideal binding conformation is not excluded from the available range of conformers.

Expanding the substrate scope of Ugi five-center, four-component reaction U-5C-4CR): ketones as coupling partners for secondary amino acids

Various symmetrical and unsymmetrical ketones were successfully coupled with secondary amino acids in the course of Ugi five-center, four-component reaction (U-5C-4CR), thus expanding the molecular diversity possible to be achieved by the reaction. The chemical yields depended on the degree of hindrance of the components employed and were satisfactory in view of possible steric interactions in the U-5C-4CR zwitterionic intermediate. The sense of diastereoinduction for reactions employing unsymmetrical ketones was examined by converting the resulting Ugi adducts into the corresponding rigid 2,6-diketopiperazine derivatives.

Copper ferrite nanoparticles: an efficient and reusable nanocatalyst for a green one-pot, three-component synthesis of spirooxindoles in water

A green reaction of isatins, active cyanomethanes, and cyclic 1,3-dicarbonyl derivatives for the efficient and simple one-pot three-component synthesis of spirooxindole fused heterocycles in refluxing water by use of magnetically recoverable and reusable catalyst is reported. The features of this procedure are, the use of magnetically recoverable and reusable catalyst, mild reaction conditions, high to excellent product yields, operational simplicity, and easy workup procedures. Most importantly of all, easy magnetic separation of the catalyst eliminates the requirement of catalyst filtration after completion of the reaction. Furthermore, the catalyst remained highly active even after 5 repeated uses.