Bicyclic Conformationally Restricted Diamines

Recent advances in electrochemical 1,2-difunctionalization of alkenes: mechanisms and perspectives

In recent years, significant achievements have been made in the field of electroorganic chemistry regarding the difunctionalization of alkenes. Researchers have developed innovative strategies utilizing the unique reactivity of electrochemical processes to synthesize complex molecules with high regioselectivity and stereoselectivity. This technology is widely applied in the total synthesis of natural products and in the pharmaceutical industry. This article reviews the research progress in the electrochemical difunctionalization of alkenes through three different radical-mediated pathways over the past five years. It includes discussions on 1,2-stereoselective and non-diastereoselective difunctionalization reactions, rearrangements, intramolecular migrations, and cyclization processes. The summary emphasizes innovative electrode designs, reaction mechanisms, and the integration with other emerging technologies, highlighting the potential of this method in modern organic chemistry. Additionally, it aims to address current challenges and propose possible solutions, providing a promising direction for electrochemically mediated difunctionalization reactions of alkenes.

(S)-3-(3,4-Dihydroxybenzyl) piperazine-2,5-dione (cyclo-Gly-L-DOPA or CG-Nio-CGLD) peptide loaded in Chitosan Glutamate-Coated Niosomes as anti-Colorectal cancer activity

BACKGROUND

Colorectal cancer (CRC), now the second most prevalent malignant tumor worldwide, is more prevalent in young adults. In recent decades, there has been progress in creating anti-colorectal cancer medications, including cytotoxic compounds.

OBJECTIVES

Novel anticancer drugs are needed to surmount existing obstacles. A recent study investigated the effectiveness of novel formulations in preventing colorectal cancer.

METHODS

During this study, we assessed a new kind of niosome called cyclo-Gly-L-DOPA (CG-Nio-CGLD) made from chitosan glutamate. We evaluated the anti-colorectal cancer properties of CG-Nio-CGLD utilizing CCK-8, invasion assay, MTT assay, flow cytometry, and cell cycle analysis. The transcription of genes associated with apoptosis was analyzed using quantitative real-time PCR. At the same time, the cytotoxicity of nanomaterials on both cancer and normal cell lines was assessed using MTT assays. Novel anticancer drugs are needed to surmount existing obstacles. A recent study investigated the effectiveness of newly developed formulations in preventing colorectal cancer.

RESULTS

The Nio-CGLD and CG-Nio-CGLD were spherical mean diameters of 169.12 ± 1.87 and 179.26 ± 2.17 nm, respectively. Entrapment efficiency (EE%) measurements of the Nio-CGLD and CG-Nio-CGLD were 63.12 ± 0.51 and 76.43 ± 0.34%, respectively. In the CG-Nio-CGLD group, the percentages of early, late, necrotic, and viable CL40 cells were 341.93%, 23.27%, 9.32%, and 25.48%. The transcription of the genes PP53, cas3, and cas8 was noticeably higher in the treatment group compared to the control group (P > 0.001). Additionally, the treatment group had lower BCL2 and survivin gene expression levels than the control group (P < 0.01). Additionally, CG-Nio-CGLD formulations demonstrated a biocompatible nanoscale delivery mechanism and displayed little cytotoxicity toward the CCD 841 CoN reference cell line.

CONCLUSION

These findings indicate that chitosan-based noisome encapsulation may enhance the effectiveness of CG-Nio-CGLD formulations in fighting cancer.

Catalytic asymmetric synthesis of 1,2-diamines

The asymmetric catalytic synthesis of 1,2-diamines has received considerable interest, especially in the last ten years, due to their presence in biologically active compounds and their applications for the development of synthetic building blocks, chiral ligands and organocatalysts. Synthetic strategies based on C-N bond-forming reactions involve mainly (a) ring opening of aziridines and azabenzonorbornadienes, (b) hydroamination of allylic amines, (c) hydroamination of enamines and (d) diamination of olefins. In the case of C-C bond-forming reactions are included (a) the aza-Mannich reaction of imino esters, imino nitriles, azlactones, isocyano acetates, and isothiocyanates with imines, (b) the aza-Henry reaction of nitroalkanes with imines, (c) imine-imine coupling reactions, and (d) reductive coupling of enamines with imines, and (e) [3+2] cycloaddition with imines. C-H bond forming reactions include hydrogenation of CN bonds and C-H amination reactions. Other catalytic methods include desymmetrization reactions of meso-diamines.

A quantum mechanistic investigation into the unusual reactions of nitrilimine and nitrile oxide with 2,3,4,5-tetraphenylcyclopentadienone

CONTEXT

The theoretical study investigates the [3 + 2] cycloaddition (32CA) reactions between C, N-diphenyl nitrilimine with 2,3,4,5-tetraphenylcyclopentadienone and benzonitrile oxide with 2,3,4,5-tetraphenylcyclopentadienone. Nitrilimines and nitrile oxides are dipoles used in the synthesis of several heterocyclic compounds, including spiropyrazoline oxindoles and isoxazolines. The derivatives of these compounds are found with different biological activities, such as ion channel blockers, anti-inflammatory and anticancer agents as well as antimalarial. Conceptual density functional theory (CDFT) analysis, along with the activation energies of the 32CA reaction between C, N-diphenyl nitrilimine with 2,3,4,5-tetraphenylcyclopentadienone, demonstrates concordance with the empirical findings. The 32CA reaction is found to proceed through a very polar single-step asynchronous mechanism. While deductions from the activation energies of the 32CA reaction between benzonitrile oxide and 2,3,4,5-tetraphenylcyclopentadienone are found to lead to the experimental product, the parr function analysis could not explain the observed chemo- and regioselectivity. This 32CA reaction is also found to proceed through a one-step asynchronous mechanism, though with a non-polar character. The modulation of substituents positioned at the reactive sites of the reactants is found to influence the kinetics, thermodynamics, and CDFT parameters of the two 32CA reactions, consequently impacting the observed selectivities.

METHODS

The 32CA reactions between C, N-diphenyl nitrilimine with 2,3,4,5-tetraphenylcyclopentadienone and benzonitrile oxide with 2,3,4,5-tetraphenylcyclopentadienone have been explored theoretically using the density functional theory method at the hybrid ωB97X-D coupled with the split valence triple-ξ (TZ) basis set as implemented in the Gaussian 09. Solvent effects were taken into account by full optimization of the gas phase geometries through the polarizable continuum model developed within the self-consistent reaction field.

A Conformationally Restricted Gold(III) Complex Elicits Antiproliferative Activity in Cancer Cells

Diamine ligands are effective structural scaffolds for tuning the reactivity of transition-metal complexes for catalytic, materials, and phosphorescent applications and have been leveraged for biological use. In this work, we report the synthesis and characterization of a novel class of cyclometalated [C^N] Au(III) complexes bearing secondary diamines including a norbornane backbone, (2R,3S)-N2,N3-dibenzylbicyclo[2.2.1]heptane-2,3-diamine, or a cyclohexane backbone, (1R,2R)-N1,N2-dibenzylcyclohexane-1,2-diamine. X-ray crystallography confirms the square-planar geometry and chirality at nitrogen. The electronic character of the conformationally restricted norbornane backbone influences the electrochemical behavior with redox potentials of -0.8 to -1.1 V, atypical for Au(III) complexes. These compounds demonstrate promising anticancer activity, particularly, complex 1, which bears a benzylpyridine organogold framework, and supported by the bicyclic conformationally restricted diaminonorbornane, shows good potency in A2780 cells. We further show that a cellular response to 1 evokes reactive oxygen species (ROS) production and does not induce mitochondrial dysfunction. This class of complexes provides significant stability and reactivity for different applications in protein modification, catalysis, and therapeutics.

Simmons-Smith Cyclopropanation: A Multifaceted Synthetic Protocol toward the Synthesis of Natural Products and Drugs: A Review

Simmons-Smith cyclopropanation is a widely used reaction in organic synthesis for stereospecific conversion of alkenes into cyclopropane. The utility of this reaction can be realized by the fact that the cyclopropane motif is a privileged synthetic intermediate and a core structural unit of many biologically active natural compounds such as terpenoids, alkaloids, nucleosides, amino acids, fatty acids, polyketides and drugs. The modified form of Simmons-Smith cyclopropanation involves the employment of Et2Zn and CH2I2 (Furukawa reagent) toward the total synthesis of a variety of structurally complex natural products that possess broad range of biological activities including anticancer, antimicrobial and antiviral activities. This review aims to provide an intriguing glimpse of the Furukawa-modified Simmons-Smith cyclopropanation, within the year range of 2005 to 2022.

A Comprehensive Overview of the Antibiotics Approved in the Last Two Decades: Retrospects and Prospects

Due to the overuse of antibiotics, bacterial resistance has markedly increased to become a global problem and a major threat to human health. Fortunately, in recent years, various new antibiotics have been developed through both improvements to traditional antibiotics and the discovery of antibiotics with novel mechanisms with the aim of addressing the decrease in the efficacy of traditional antibiotics. This manuscript reviews the antibiotics that have been approved for marketing in the last 20 years with an emphasis on the antibacterial properties, mechanisms, structure-activity relationships (SARs), and clinical safety of these antibiotics. Furthermore, the current deficiencies, opportunities for improvement, and prospects of antibiotics are thoroughly discussed to provide new insights for the design and development of safer and more potent antibiotics.

Cis-Selective Double Spirocyclization via Dearomatization and Isomerization under Thermodynamic Control

Spiro compounds have been considered key scaffolds for pharmaceutical applications. Although many synthetic methods exist for monospirocycles, fewer approaches are known for dispirocycles. Here, we report a highly cis-selective method for constructing a 5/6/5-dispirocyclic structure containing pyrrolidine and γ-lactam rings with various substituents from a series of N-arylpropiolamides. The high cis-selectivity would result from isomerization under thermodynamic control. Cis- and trans-diastereomers can be in equilibrium, favoring cis-adducts.

On drug discovery against infectious diseases and academic medicinal chemistry contributions

This perspective is an attempt to document the problems that medicinal chemists are facing in drug discovery. It is also trying to identify relevant/possible, research areas in which academics can have an impact and should thus be the subject of grant calls. Accordingly, it describes how hit discovery happens, how compounds to be screened are selected from available chemicals and the possible reasons for the recurrent paucity of useful/exploitable results reported. This is followed by the successful hit to lead stories leading to recent and original antibacterials which are, or about to be, used in human medicine. Then, illustrated considerations and suggestions are made on the possible inputs of academic medicinal chemists. This starts with the observation that discovering a "good" hit in the course of a screening campaign still rely on a lot of luck - which is within the reach of academics -, that the hit to lead process requires a lot of chemistry and that if public-private partnerships can be important throughout these stages, they are absolute requirements for clinical trials. Concerning suggestions to improve the current hit success rate, one academic input in organic chemistry would be to identify new and pertinent chemical space, design synthetic accesses to reach these and prepare the corresponding chemical libraries. Concerning hit to lead programs on a given target, if no new hits are available, previously reported leads along with new structural data can be pertinent starting points to design, prepare and assay original analogues. In conclusion, this text is an actual plea illustrating that, in many countries, academic research in medicinal chemistry should be more funded, especially in the therapeutic area neglected by the industry. At the least, such funds would provide the intensive to secure series of hopefully relevant chemical entities which appears to often lack when considering the results of academic as well as industrial screening campaigns.

Applications of Isosteres of Piperazine in the Design of Biologically Active Compounds: Part 1

Piperazine and homopiperazine are well-studied heterocycles in drug design that have found gainful application as scaffolds and terminal elements and for enhancing the aqueous solubility of a molecule. The optimization of drug candidates that incorporate these heterocycles in an effort to refine potency, selectivity, and developability properties has stimulated the design and evaluation of a wide range of bioisosteres that can offer advantage. In this review, we summarize the design and application of bioisosteres of piperazine and homopiperazine that have almost exclusively been in the drug design arena. While there are ∼100 approved drugs that incorporate a piperazine ring, only a single marketed agricultural product is built on this heterocycle. As part of the review, we discuss some of the potential reasons underlying the relatively low level of importance of this heterocycle to the design of agrochemicals and highlight the potential opportunities for their use in contemporary research programs.

Cu-Electrocatalytic Diazidation of Alkenes at ppm Catalyst Loading

The 1,2-diamine motif is prevalent in natural products, small-molecule pharmaceuticals, and catalysts for asymmetric synthesis. Transition metal catalyzed alkene diazidation has evolved to be an attractive strategy to access vicinal primary diamines but remains challenging, especially for practical applications, due to the restriction to a certain type of olefins, the frequent use of chemical oxidants, and the requirement for high loadings of metal catalysts (1 mol % or above). Herein we report a scalable Cu-electrocatalytic alkene diazidation reaction with 0.02 mol % (200 ppm) of copper(II) acetylacetonate as the precatalyst without exogenous ligands. In addition to its use of low catalyst loading, the electrocatalytic method is scalable, compatible with a broad range of functional groups, and applicable to the diazidation of α,β-unsaturated carbonyl compounds and mono-, di-, tri-, and tetrasubstituted unactivated alkenes.

Modulating physicochemical properties of tetrahydropyridine-2-amine BACE1 inhibitors with electron-withdrawing groups: A systematic study

A common challenge for medicinal chemists is to reduce the pK_a of strongly basic groups' conjugate acids into a range that preserves the desired effects, usually potency and/or solubility, but avoids undesired effects like high volume of distribution (V_d), limited membrane permeation, and off-target binding to, notably, the hERG channel and monoamine receptors. We faced this challenge with a 3,4,5,6-tetrahydropyridine-2-amine scaffold harboring an amidine, a key structural component of potential inhibitors of BACE1, the rate-limiting enzyme in the production of Aβ species that make up amyloid plaques in Alzheimer's disease. In our endeavor to balance potency with desirable properties to achieve brain penetration, we introduced a diverse set of groups in beta position of the amidine that modulate logD, PSA and pK_a. Given the synthetic challenge to prepare these highly functionalized warheads, we first developed a design flow including predicted physicochemical parameters which allowed us to select only the most promising candidates for synthesis. For this we evaluated a set of commercial packages to predict physicochemical properties, which can guide medicinal chemists in their endeavors to modulate pK_a values of amidine and amine bases.

A Close-up Look at the Chemical Space of Commercially Available Building Blocks for Medicinal Chemistry

The ability to efficiently synthesize desired compounds can be a limiting factor for chemical space exploration in drug discovery. This ability is conditioned not only by the existence of well-studied synthetic protocols but also by the availability of corresponding reagents, so-called building blocks (BBs). In this work, we present a detailed analysis of the chemical space of 400 000 purchasable BBs. The chemical space was defined by corresponding synthons─fragments contributed to the final molecules upon reaction. They allow an analysis of BB physicochemical properties and diversity, unbiased by the leaving and protective groups in actual reagents. The main classes of BBs were analyzed in terms of their availability, rule-of-two-defined quality, and diversity. Available BBs were eventually compared to a reference set of biologically relevant synthons derived from ChEMBL fragmentation, in order to illustrate how well they cover the actual medicinal chemistry needs. This was performed on a newly constructed universal generative topographic map of synthon chemical space that enables visualization of both libraries and analysis of their overlapped and library-specific regions.

Diamine Synthesis via the Nitrogen-Directed Azidation of σ- and π-C-C Bonds

Diamines are essential building blocks for the synthesis of agrochemicals, drugs, and organic materials, yet their synthesis remains challenging, as both nitrogens need to be differentiated and diverse substitution patterns (1,2, 1,3, or 1,4) are required. We report herein a new strategy giving access to 1,2, 1,3, and 1,4 amido azides as orthogonally protected diamines based on the nitrogen-directed diazidation of alkenes, cyclopropanes, and cyclobutanes. Commercially available copper thiophene-2-carboxylate (CuTc, 2 mol %) as catalyst promoted the diazidation of both π and σ C-C bonds within 10 min in the presence of readily available oxidants and trimethylsilyl azide. Selective substitution of the formed α-amino azide by carbon nucleophiles (electron-rich aromatic, malonate, organosilicon, organoboron, organozinc, and organomagnesium compounds) was then achieved in a one-pot fashion, leading to the formation of 1,2-, 1,3-, and 1,4-diamines with the amino groups protected orthogonally as an amide/carbamate and an azide.

6-Hydroxymethyl Indolizidin-2-one Amino Acid Synthesis, Conformational Analysis, and Biomedical Application as Dipeptide Surrogates in Prostaglandin-F2α Modulators

6-Hydroxymethyl indolizidin-2-one amino acids were synthesized in 10 steps from l-serine by intramolecular ring opening of a symmetrical epoxide and lactam formation. X-ray analyses indicated the bicycles replicated ideal peptide type II' β-turn central dihedral angle geometry. Inside a prostaglandin-F_2α receptor modulator, the 6-hydroxymethyl analogue retained inhibitory activity on myometrial contractility.

Photoredox-Catalyzed Decarboxylative Cross-Coupling of α-Amino Acids with Nitrones

A decarboxylative cross-coupling reaction of α-amino acids with nitrones via visible-light-induced photoredox catalysis has been established for easy access to β-amino hydroxylamines and vicinal diamines with structural diversity, which is featured with simple operation, mild conditions, readily available α-amino acids, and a broad scope of nitrone substrates. The application of this protocol can furnish efficient synthetic strategies for some valuable vicinal diamine-containing molecules.

Highly diastereoselective synthesis of vicinal diamines via a Rh-catalyzed three-component reaction of diazo compounds with diarylmethanimines and ketimines

A Rh-catalyzed selective three-component reaction of diazo compounds with diarylmethanimines and ketimines is reported that offers an efficient and convenient access to vicinal diamine derivatives with two tertiary stereocenters in high yields.

Iridium(I)-Catalyzed α-C(sp3)-H Alkylation of Saturated Azacycles

Saturated azacycles are commonly encountered in bioactive compounds and approved therapeutic agents. The development of methods for functionalization of the α-methylene C-H bonds of these highly privileged building blocks is of great importance, especially in drug discovery. While much effort has been dedicated toward this goal by using a directed C-H activation approach, the development of directing groups that are both general as well as practical remains a significant challenge. Herein, the design and development of novel amidoxime directing groups is described for Ir(I)-catalyzed α-C(sp³)-H alkylation of saturated azacycles using readily available olefins as coupling partners. This protocol extends the scope of saturated azacycles to piperidines, azepane, and tetrahydroisoquinoline that are incompatible with our previously reported directing group. A variety of olefin coupling partners, including previously unreactive disubstituted terminal olefins and internal olefins, are compatible with this transformation. The selectivity for a branched α-C(sp³)-alkylation product is also observed for the first time when acrylate is used as the reaction partner. The development of practical, one-step installation and removal protocols further adds to the utility of amidoxime directing groups.

A Molecular Electron Density Theory Study of the Synthesis of Spirobipyrazolines through the Domino Reaction of Nitrilimines with Allenoates

The reaction of diphenyl nitrilimine (NI) with methyl 1-methyl-allenoate yielding a spirobipyrazoline has been studied within molecular electron density theory (MEDT) at the MPWB1K/6-311G(d) computational level in dichloromethane. This reaction is a domino process that comprises two consecutive 32CA reactions with the formation of a pyrazoline intermediate. Analysis of the relative Gibbs free energies indicates that both 32CA reactions are highly regioselective, the first one being also completely chemoselective, in agreement with the experimental outcomes. The geometries of the TSs indicate that they are associated to asynchronous bond formation processes in which the shorter distance involves the C1 carbon of diphenyl NI. Despite the zwitterionic structure of diphenyl NI, the appearance of a pseudoradical structure at the beginning of the reaction path, with a very low energy cost, suggests that the 32CA reaction between diphenyl NI, a strong nucleophile, and the allenoate, a moderate electrophile, should be mechanistically considered on the borderline between pmr-type and cb-type 32CA reactions, somewhat closer to the latter.

The Symbiotic Relationship Between Drug Discovery and Organic Chemistry

All pharmaceutical products contain organic molecules; the source may be a natural product or a fully synthetic molecule, or a combination of both. Thus, it follows that organic chemistry underpins both existing and upcoming pharmaceutical products. The reverse relationship has also affected organic synthesis, changing its landscape towards increasingly complex targets. This Review article sets out to give a concise appraisal of this symbiotic relationship between organic chemistry and drug discovery, along with a discussion of the design concepts and highlighting key milestones along the journey. In particular, criteria for a high-quality compound library design enabling efficient virtual navigation of chemical space, as well as rise and fall of concepts for its synthetic exploration (such as combinatorial chemistry; diversity-, biology-, lead-, or fragment-oriented syntheses; and DNA-encoded libraries) are critically surveyed.

Stereoselective Construction of Methylenecyclobutane-Fused Indolines through Photosensitized [2+2] Cycloaddition of Allene-Tethered Indole Derivatives

Irradiation of 1-(hexa-4,5-dienoyl)indole derivatives in the presence of an aromatic ketone by a high-pressure mercury lamp through Pyrex glass gave the corresponding cyclized products stereoselectively in high yields. The major part of the products was an all- cis-fused methylenecyclobutane-type compound produced through [2+2] cycloaddition, accompanied by small amounts of alkynes via 1,5-hydrogen transfer of a biradical intermediate. Among a range of aromatic ketones, 3',4'-dimethoxyacetophenone was found to sensitize the substrate quite effectively.

Visible-light activated metal catalyst-free vicinal diazidation of olefins with sulfonium iodate(i) species

An unprecedented visible-light inspired selective radical azidation of unactivated and diverse substituted vinylarenes with sulfonium iodate reagent has been realized. The intrinsic radical process triggered by light tolerated several synthetically useful functionalities enabling two new carbon-hetero bonds which display distinctive late-stage applications to biologically relevant scaffolds.

Scalable synthesis and properties of 7-methyl- 4-azaindole

An approach to the synthesis of 7-methyl-4-azaindole, which is a valuable building block for drug discovery programs, is described. The method relies on using a bromine atom as a ‘place holding group’ for one of the carbon atoms of the pyridine ring throughout the reaction sequence, and it is removed only upon the final reductive cyclization leading to the azaindole ring. Exhaustive hydrogenation of the target product proceeds in a diastereoselective manner and leads to a bicyclic conformationally restricted diamine derivative.

Enantioselective Synthesis of 1,2-Diamines Containing Tertiary and Quaternary Centers through Rhodium-Catalyzed DYKAT of Racemic Allylic Trichloroacetimidates

The amination of racemic secondary and tertiary allylic trichloroacetimidates possessing β-nitrogen substituents and proximal nitrogen-containing heterocycles, via chiral diene-ligated rhodium-catalyzed dynamic kinetic asymmetric transformations (DYKAT), provides branched allylic 1,2-diamines with high enantioselectivity. The catalytic system can be applied to the synthesis of 1,2-diamines possessing two contiguous stereocenters with excellent diastereoselectivity. Furthermore, the nitrogen-containing heterocycles suppress competing vinyl azirdine formation, allowing for the high enantioselective syntheses of 1,2-diamines possessing tertiary and quaternary centers.

Synthesis of Spirobidihydropyrazole through Double 1,3-Dipolar Cycloaddition of Nitrilimines with Allenoates

The double 1,3-dipolar cycloaddition of allenoates with nitrilimines has been achieved under mild reaction conditions, affording a variety of spirobidihydropyrazoles in moderate to excellent yields with excellent diastereoselectivities. The reaction diastereoselectively constructs double dihydropyrazole moieties and two chiral centers including a spiro carbon center.

Regio- and Stereocontrolled Synthesis of 3-Substituted 1,2-Diazetidines by Asymmetric Allylic Amination of Vinyl Epoxide

Pd-catalyzed asymmetric allylic amination of rac-vinyl epoxide with unsymmetrical 1,2-hydrazines proceeds with excellent regio- and stereocontrol, which after further ring closure provides differentially protected 3-vinyl-1,2-diazetidines in good yields. The chirality at C-3 exerts stereocontrol over the nitrogen centers in the 1,2-diazetidine with all substituents orientating themselves trans to their neighbors. Efficient functionalization without rupture of the strained ring is demonstrated (e.g., by cross-metathesis), establishing the first general route to C-3-substituted 1,2-diazetidines in enantioenriched form.