Asymmetric Transfer Hydrogenation as a Key Step in the Synthesis of the Phosphonic Acid Analogs of Aminocarboxylic Acids

α-Aminophosphonic acids have a remarkably broad bioactivity spectrum. They can function as highly efficient transition state mimics for a variety of hydrolytic and angiotensin-converting enzymes, which makes them interesting target structures for synthetic chemists. In particular, the phosphonic acid analogs to α-aminocarboxylic acids (Pa AAs) are potent enzyme inhibitors, but many of them are only available by chiral or enzymatic resolution; sometimes only one enantiomer is accessible, and several have never been prepared in enantiopure form at all. Today, a variety of methods to access enantiopure α-aminophosphonic acids is known but none of the reported approaches can be generally applied for the synthesis of Pa AAs. Here we show that the phosphonic acid analogs of many (proteinogenic) α-amino acids become accessible by the catalytic, stereoselective asymmetric transfer hydrogenation (ATH) of α-oxo-phosphonates. The highly enantioenriched (enantiomeric excess (ee) ≥ 98 %) α-hydroxyphosphonates obtained are important pharmaceutical building blocks in themselves and could be easily converted to α-aminophosphonic acids in most studied cases. Even stereoselectively deuterated analogs became easily accessible from the same α-oxo-phosphonates using deuterated formic acid (DCO2 H).

Chromone Containing Hybrid Analogs: Synthesis and Applications in Medicinal Chemistry

The use of privileged scaffolds has proven beneficial for generating novel bioactive scaffolds in drug discovery program. Chromone is one such privileged scaffold that has been exploited for designing pharmacologically active analogs. The molecular hybridization technique combines the pharmacophoric features of two or more bioactive compounds to avail a better pharmacological activity in the resultant hybrid analogs. The current review summarizes the rationale and techniques involved in developing hybrid analogs of chromone, which show potential in fields of obesity, diabetes, cancer, Alzheimer's disease and microbial infections. Here the molecular hybrids of chromone with various pharmacologically active analogs or fragments (donepezil, tacrine, pyrimidines, azoles, furanchalcones, hydrazones, quinolines, etc.) are discussed with their structure-activity relationship against above-mentioned diseases. Detailed methodologies for the synthesis of corresponding hybrid analogs have also been described, with suitable synthetic schemes. The current review will shed light on various strategies utilized for the design of hybrid analogs in the field of drug discovery. The importance of hybrid analogs in various disease conditions is also illustrated.

Synthesis of Tetrasubstituted Phosphorus Analogs of Aspartic Acid as Antiproliferative Agents

An efficient general method for the synthesis of a wide family of α-aminophosphonate analogs of aspartic acid bearing tetrasubstituted carbons is reported through an aza-Reformatsky reaction of α-iminophosphonates, generated from α-aminophosphonates, in an umpolung process. In addition, the α-aminophosphonate substrates showed in vitro cytotoxicity, inhibiting the growth of carcinoma human tumor cell lines A549 (carcinomic human alveolar basal epithelial cell) and SKOV3 (human ovarian carcinoma). In view of the possibilities in the diversity of the substituents that offer the synthetic methodology, an extensive profile structure-activity is presented, measuring IC₅₀ values up to 0.34 µM in the A549 and 9.8 µM in SKOV3 cell lines.

Antileishmanial Activities of ( Z )-2-(Nitroimidazolylmethylene)-3( 2H )-Benzofuranones: Synthesis, In Vitro Assessment, and Bioactivation by NTR 1 and 2

The antileishmanial activity of a series of ( Z )-2-(heteroarylmethylene)-3(2 H )-benzofuranone derivatives, possessing 5-nitroimidazole or 4-nitroimidazole moieties, was investigated against Leishmania major promastigotes and some analogues exhibited prominent activities. Compounds with IC 50 values lower than 20 μM were further examined against L. donovani axenic amastigotes.

Synthesis of Functionalized Azepines via Cu(I)-Catalyzed Tandem Amination/Cyclization Reaction of Fluorinated Allenynes

An efficient method for the selective preparation of trifluoromethyl-substituted azepin-2-carboxylates and their phosphorous analogues has been developed via Cu(I)-catalyzed tandem amination/cyclization reaction of functionalized allenynes with primary and secondary amines.

Silver Catalyzed One-Pot Three-Component Synthesis of α-Aminonitriles and Biologically Relevant α-Amino-phosphonates

A simple silver salt (AgSbF6) catalyzed aminophosphonylation and Strecker reaction have been developed and successfully applied to a wide range of substrates (>55 substrates). This solvent-, ligand-, and base-free one-pot three component protocol operates effectively at room temperature to provide diversified α-aminophosphonates and α-aminonitriles, which gave access to the respective α-amino amides. Importantly, the present catalyst system is also capable to produce the rarely reported and biologically relevant aminophosphonates (having anti-leishmanial activity). Further, the mechanistic studies reveal that the present phosphonylation protocol follows a radical pathway.

Recent Advances in Multicomponent Reactions Catalysed under Operationally Heterogeneous Conditions

Multicomponent reactions (MCRs) have been gaining significance and attention over the past decade because of their ability to furnish complex products by using readily available and simple starting materials while simultaneously eliminating the need to separate and purify any intermediates. More so, most of these products have been found to exhibit diverse biological activities. Another paradigm shift which has occurred contemporarily is the switch to heterogeneous catalysis, which results in additional benefits such as the reduction of waste and an increase in the safety of the process. More importantly, it allows the user to recover and reuse the catalyst for multiple runs. In summary, both methodologies adhere to the principles of green chemistry, a philosophy which needs to become overarchingly enshrined. The plethora of reactions and catalysts which have been developed gives hope that chemists are slowly changing their ideology. As a result, this review attempts to discuss multicomponent reactions catalysed by operationally heterogeneous catalysts in the past 10 years. In this review, a further distinction is made between the MCRs which lead to the formation of heterocycles and those which do not.

Relationship between Structure and Antibacterial Activity of α-Aminophosphonate Derivatives Obtained via Lipase-Catalyzed Kabachnik-Fields Reaction

We reported a new method dealing with the synthesis of novel pharmacologically relevant α-aminophosphonate derivatives via a lipase-catalyzed Kabachnik−Fields reaction with yields of up to 93%. The advantages of this protocol are excellent yields, mild reaction conditions, low costs, and sustainability. The developed protocol is applicable to a range of H-phosphites and organic amines, providing a wide substrate scope. A new class of α-aminophosphonate analogues possessing P-chiral centers was also synthesized. The synthesized compounds were characterized on the basis of their antimicrobial activities against E. coli. The impact of the various alkoxy groups on antimicrobial activity was demonstrated. The crucial role of the substituents, located at the aromatic rings in the phenylethyloxy and benzyloxy groups, on the inhibitory action against selected pathogenic E. coli strains was revealed. The observed results are especially important because of increasing resistance of bacteria to various drugs and antibiotics.

Synthesis of hybrid phosphorated indenoquinolines and biological evaluation as topoisomerase I inhibitors and antiproliferative agents

This work describes the first synthesis of diethyl 6,6a,7,11b-tetrahydro-5H-indeno[2,1-c]quinolinylphosphonates 5, diethyl 7H-indeno[2,1-c]quinolinylphosphonates 6 and diethyl 7-oxo-7H-indeno[2,1-c]quinolinylphosphonates 7, which were prepared in good to high overall yields. The synthetic route involves a multicomponent reaction of 2-phosphonateaniline, aldehydes and indene as olefin and allows the selective generation of three stereogenic centres in a short, efficient and reliable manner. The selective dehydrogenation of 1,2,3,4-tetrahydroindenoquinolines leads to the formation of corresponding indenoquinolines, and subsequent oxidation of methylene group of the indenoquinolines allows the access to indenoquinolinones.

Indium promoted C(sp3)–P bond formation by the Domino A3-coupling method – a combined experimental and computational study

An efficient catalytic process for the synthesis of α-aminophosphonates is developed by a one-pot three-component reaction in the presence of In complexes at room temperature. DFT based mechanistic studies of the catalytic reactions are reported.

Transition Metal-free Approach for the Synthesis of 2-substituted Quinazolin-4(3H)-one via Anhydrous Magnesium Perchlorate

Background:

A convenient and efficient methodology for the synthesis of quinazolin- 4(3H)-ones from simple and readily available 2-amino benzamides and aromatic aldehydes in ethanol using Magnesium perchlorate are being reported in the present study. Good to excellent isolated yields (68-95%) of the corresponding 2-substituted quinazolinones were obtained under mild reaction conditions with excellent functional group tolerance. The affordability of the catalyst, the wide availability of the starting materials, transition metal free synthesis and the simplicity of the procedure renders the present methodology useful in organic synthesis.

Objective:

A maneuver methodology developed for the synthesis of quinazolin-4(3H)-ones via using Magnesium perchlorate from 2-amino benzamides and aromatic aldehydes in ethanol.

Methods:

10% mol anhydrous Magnesium perchlorate in presence of ethanol give to simply rapid formation of Quinazolin-4(3H)-ones from 1 mole of 2-amino benzamides and 1 mole of aromatic aldehydes.

Results:

Screening results of Anti-leishmanial showed that out of the synthesized series of 12 compounds, compounds 3c, 3d, 3g, 3h and 3i showed significant antileishmanial activities (L. donavani) with IC50 values 8.39, 9.37, 9.43, 7.1 and 8.7 μM.

Conclusion:

In summary, we have developed convenient synthesis of quinazolin-4(3H)-one, from simple and easily available precursor employing anhydrous Mg(ClO4)2 under green conditions.

Synthesis of new curcumin-based aminocarbonitrile derivatives incorporating 4H-pyran and 1,4-dihydropyridine heterocycles

A multicomponent reaction containing curcumin, aldehydes, malononitrile and amine was developed for the one-pot synthesis of a novel library of 4H-pyran and 1,4-dihyropyridin heterocycles incorporating curcumin moiety. The products were obtained in the presence of p-toluenesulfonic acid as catalyst in ethanol as solvent in good to excellent yields.

Design, synthesis and evaluation of new chromone-derived aminophosphonates as potential acetylcholinesterase inhibitor

A series of novel N-substituted α-aminophosphonates-bearing chromone moiety were synthesized and evaluated for acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) activities and antioxidant properties. Porcine pancreatic lipase was employed as a catalyst. Inhibitory activity against AChE ranged between 0.103 and 5.781 µM, whereas for BuChE, activities ranged between 8.619 and 18.789 µM. The results show that among the various synthesized compounds, strongest AChE inhibition was found for the compound containing aliphatic amine analogs, while in case of BuChE, aromatic amines showed better activity as compared to aliphatic amines. Compound 4j was found to be the most potent inhibitor of AChE with an IC₅₀ value of 0.103 ± 0.24 μM and inhibited AChE through mixed-type inhibition. Compound 4j was twofolds more potent than tacrine, 35-folds potent than galantamine and 50-folds potent than rivastigmine. Also, docking study revealed that compound 4j binds to both the peripheral anionic site and catalytic anionic site of AChE and BuChE. The antioxidant activities of synthesized compounds were performed against 2,2-diphenyl-1-picrylhydrazyl and hydrogen peroxide scavenging. DNA nicking activity of selected compounds also suggested that the compounds do not harm plasmid DNA pBR322. Compound 4j also showed significant DNA damage protection activity. Novel N-substituted α-aminophosphonates bearing chromone moiety were synthesized and evaluated for anti-acetylcholinesterase, anti-butyrylcholinesterase, antioxidant and DNA damage activities.

Synthesis of Biologically Active Molecules through Multicomponent Reactions

Focusing on the literature progress since 2002, the present review explores the highly significant role that multicomponent reactions (MCRs) have played as a very important tool for expedite synthesis of a vast number of organic molecules, but also, highlights the fact that many of such molecules are biologically active or at least have been submitted to any biological screen. The selected papers covered in this review must meet two mandatory requirements: (1) the reported products should be obtained via a multicomponent reaction; (2) the reported products should be biologically actives or at least tested for any biological property. Given the diversity of synthetic approaches utilized in MCRs, the highly diverse nature of the biological activities evaluated for the synthesized compounds, and considering their huge structural variability, much of the reported data are organized into concise schemes and tables to facilitate comparison, and to underscore the key points of this review.

Synthesis of α-CF3-substituted E-dehydroornithine derivatives via copper(i)-catalyzed hydroamination of allenes

Novel α-CF₃-substituted E-dehydroornithine derivatives have been synthesized via the Cu(i)-catalyzed hydroamination of α-CF₃-α-allenyl-α-aminocarboxylates/phosphonates with different amines.

Chemoinformatics Strategies for Leishmaniasis Drug Discovery

Leishmaniasis is a fatal neglected tropical disease (NTD) that is caused by more than 20 species of Leishmania parasites. The disease kills approximately 20,000 people each year and more than 1 billion are susceptible to infection. Although counting on a few compounds, the therapeutic arsenal faces some drawbacks such as drug resistance, toxicity issues, high treatment costs, and accessibility problems, which highlight the need for novel treatment options. Worldwide efforts have been made to that aim and, as well as in other therapeutic areas, chemoinformatics have contributed significantly to leishmaniasis drug discovery. Breakthrough advances in the comprehension of the parasites’ molecular biology have enabled the design of high-affinity ligands for a number of macromolecular targets. In addition, the use of chemoinformatics has allowed highly accurate predictions of biological activity and physicochemical and pharmacokinetics properties of novel antileishmanial compounds. This review puts into perspective the current context of leishmaniasis drug discovery and focuses on the use of chemoinformatics to develop better therapies for this life-threatening condition.

Carbene-Catalyzed [4 + 2] Cycloadditions of Vinyl Enolate and (in Situ Generated) Imines for Enantioselective Synthesis of Quaternary α-Amino Phosphonates

A carbene-catalyzed enantioselective addition of enals to five-membered cyclic imines is developed. The reaction gives chiral quaternary α-amino phosphonates bearing tetrasubstituted carbon centers with excellent enantioselectivities. The imine substrates can be generated in situ from the corresponding amines under an oxidative condition that is compatible with the carbene catalysis. Thus, a one-pot cross-dehydrogenative-coupling (CDC) reaction between enals and amines is also realized with high enantioselectivity remaining. The method provides quick enantioselective access to amino phosphonates with potential applications in medicines and pesticides.

Antitrypanosomal and antileishmanial activity of prenyl-1,2,3-triazoles

A series of prenyl 1,2,3-triazoles were prepared from isoprenyl azides and different alkynes. The dipolar cycloaddition reaction provided exclusively primary azide products as regioisomeric mixtures that were separated by column chromatography and fully characterized. Most of the compounds displayed antiparasitic activity against Trypanosoma cruzi and Leishmania donovani. The most active compounds were assayed as potential TcCYP51 inhibitors.

New antiprotozoal agents: Synthesis and biological evaluation of different 4-(7-chloroquinolin-4-yl) piperazin-1-yl)pyrrolidin-2-yl)methanone derivatives

In an endeavor to develop efficacious antiprotozoal agents 4-(7-chloroquinolin-4-yl) piperazin-1-yl)pyrrolidin-2-yl)methanone derivatives (5-14) were synthesized, characterized and biologically evaluated for antiprotozoal activity. The compounds were screened in vitro against the HM1: IMSS strain of Entamoeba histolytica and NF54 chloroquine-sensitive strain of Plasmodium falciparum. Among the synthesized compounds six exhibited promising antiamoebic activity with IC₅₀ values (0.14-1.26μM) lower than the standard drug metronidazole (IC₅₀ 1.80μM). All nine compounds exhibited antimalarial activity (IC₅₀ range: 1.42-19.62μM), while maintaining a favorable safety profile to host red blood cells. All the compounds were less effective as an antimalarial and more toxic (IC₅₀ range: 14.67-81.24μM) than quinine (IC₅₀: 275.6±16.46μM) against the human kidney epithelial cells. None of the compounds exhibited any inhibitory effect on the viability of Anopheles arabiensis mosquito larvae.

Synthesis of new α-aminophosphonate derivatives incorporating benzimidazole, theophylline and adenine nucleobases using l-cysteine functionalized magnetic nanoparticles (LCMNP) as magnetic reusable catalyst: evaluation of their anticancer properties

A new class of α-aminophosphonate derivatives incorporating benzimidazole, theophylline and adenine nucleobases were synthesized in a three-step process and the anticancer activities of selected ligands were evaluated.

Highly efficient solvent free synthesis of α-aminophosphonates catalyzed by recyclable nano-magnetic sulfated zirconia (Fe3O4@ZrO2/SO42−)

In this project, nano-magnetic sulfated zirconia Fe₃O₄@ZrO₂/SO₄²⁻ was prepared and characterized using various instrumental methods and used in the synthesis of α-aminophosphonate derivatives in the Kabachnik–Fields reaction.

Efficient solvent free synthesis of tertiary α-aminophosphonates using H2Ti3O7 nanotubes as a reusable solid-acid catalyst

The Kabachnik–Fields reaction was applied for the synthesis of α-aminophosphonates from aldehydes, secondary amines and dialkyl phosphites in the presence of H₂Ti₃O₇ nanotubes as reusable solid-acid catalysts.

N-Arylalkylbenzo[d]thiazole-2-carboxamides as anti-mycobacterial agents: design, new methods of synthesis and biological evaluation

Benzothiazole-2-carboxyarylalkylamides are reported as a new class of potent anti-mycobacterial agents.