α‐Iminophosphonates: Useful Intermediates for Enantioselective Synthesis of α‐Aminophosphonates

Synthetic Methods for Azaheterocyclic Phosphonates and Their Biological Activity: An Update 2004-2024

The increasing importance of azaheterocyclic phosphonates in the agrochemical, synthetic, and medicinal field has provoked an intense search in the development of synthetic routes for obtaining novel members of this family of compounds. This updated review covers methodologies established since 2004, focusing on the synthesis of azaheterocyclic phosphonates, of which the phosphonate moiety is directly substituted onto to the azaheterocyclic structure. Emphasizing recent advances, this review classifies newly developed synthetic approaches according to the ring size and providing information on biological activities whenever available. Furthermore, this review summarizes information on various methods for the formation of C-P bonds, examining sustainable approaches such as the Michaelis-Arbuzov reaction, the Michaelis-Becker reaction, the Pudovik reaction, the Hirao coupling, and the Kabachnik-Fields reaction. After analyzing the biological activities and applications of azaheterocyclic phosphonates investigated in recent years, a predominant focus on the evaluation of these compounds as anticancer agents is evident. Furthermore, emerging applications underline the versatility and potential of these compounds, highlighting the need for continued research on synthetic methods to expand this interesting family.

Behavioral Effects and Analgesic Profile of Hemoglobin-Derived Valorphin and Its Synthetic Analog in Rodents

Valorphin (V1) is a naturally occurring peptide derived from hemoglobin that has been found to have an affinity for opioid receptors and exhibits antinociceptive and anticonvulsant activity. Some of its synthetic analogs containing an aminophosphonate moiety show structure-dependent potent antinociceptive effects. This study aimed to reveal a detailed picture of the antinociceptive mechanisms and behavioral effects of V1 and its recently synthesized phosphopeptide analog V2p in rodents using a range of methods. The studied peptides significantly reduced acute (mean V1-9.0, V2p-5.8 vs. controls-54.1 s) and inflammatory (mean V1-57.9 and V2p-53.3 vs. controls-107.6 s) nociceptive pain in the formalin test, as well as carrageenan-induced hyperalgesia (mean V1-184.7 and V2p-107.3 vs. controls-61.8 g) in the paw pressure test. These effects are mediated by activation of opioid receptors with a predominance of kappa in V1 antinociception and by delta, kappa, and mu receptors in V2p-induced antinociception. Both peptides did not change the levels of TNF-alpha and IL-1-beta in blood serum. V1 induces depression-like behavior, and V2p shows a tendency toward anxiolysis and short-term impairment of motor coordination without affecting exploratory behavior. The results characterize valorphin and its derivative as promising analgesics that exert their effects both centrally and peripherally, without causing severe behavioral changes in experimental animals. These encouraging data are a foundation for future studies focusing on the effects of hemorphins after long-term treatment.

The Last Decade of Optically Active α-Aminophosphonates

α-Aminophosphonates and related compounds are important due to their real and potential biological activity. α-Aminophosphonates may be prepared by the Kabachnik-Fields condensation of oxo compounds, amines and dialkyl phosphites, or by the aza-Pudovik addition of the same P-reagents to imines. In this review, the methods that allow for the synthesis of α-aminophosphonates with optical activity are surveyed. On the one hand, optically active catalysts or ligands may induce enantioselectivity during the Kabachnik-Fields reaction. On the other hand, asymmetric catalysis during the aza-Pudovik reaction, or hydrogenations of iminophosphonates, may prove to be a useful tool. Lastly yet importantly, it is possible to start from optically active reagents that may be associated with diastereoselectivity. The "green" aspects of the different syntheses are also considered.

Deamination of 1-Aminoalkylphosphonic Acids: Reaction Intermediates and Selectivity

Deamination of 1-aminoalkylphosphonic acids in the reaction with HNO₂ (generated "in situ" from NaNO₂) yields a mixture of substitution products (1-hydroxyalkylphosphonic acids), elimination products (vinylphosphonic acid derivatives), rearrangement and substitution products (2-hydroxylkylphosphonic acids) as well as H₃PO₄. The variety of formed reaction products suggests that 1-phosphonoalkylium ions may be intermediates in such deamination reactions.

Diethyl(benzamido(diisopropoxyphosphoryl)methyl) phosphonate

Bisphosphonates are widely used in medicine and related areas, mainly for the treatment of bone diseases, such as osteoporosis. However, their synthesis is usually performed under harsh reaction conditions. In order to overcome this limitation, the present work illustrates a new synthetic route to access the title α-aminobisphosphonate in milder reaction conditions using α-phosphorylated imines as key intermediates.

In(OTf)3-catalyzed N-α phosphonylation of N,O-acetals with triethyl phosphite

A practical approach to α-aminophosphonates has been developed through an In(OTf)₃-catalyzed N-α phosphonylation of N,O-acetals with triethyl phosphite 7. Indoline and isoindoline N,O-acetals 6a-6j and 9a-9j and chain N,O-acetals 11a-11p were subjected to a Lewis acid catalyzed N-α phosphonylation process. As a result, the desired α-aminophosphonates 8a-8j, 10a-10j and 12a-12p were obtained in moderate to good yields.

Hydroxy- and Amino-Phosphonates and -Bisphosphonates: Synthetic Methods and Their Biological Applications

Phosphonates and bisphosphonates are stable analogs of phosphates and pyrophosphates that are characterized by one and two carbon–phosphorus bonds, respectively. Among the various phosphonates and bisphosphonates, hydroxy and amino substitutes are of interest as effective in medicinal and industrial chemistry. For example, hydroxy bisphosphonates have proven to be effective for the prevention of bone loss, especially in osteoporotic disease. On the other hand, different substitutions on the carbon atom connected to phosphorus have led to the synthesis of many different hydroxy- and amino-phosphonates and -bisphosphonates, each with its distinct physical, chemical, biological, therapeutic, and toxicological characteristics. Dialkyl or aryl esters of phosphonate and bisphosphonate compounds undergo the hydrolysis process readily and gave valuable materials with wide applications in pharmaceutical and agriculture. This review aims to demonstrate the ongoing preparation of various classes of hydroxy- and amino-phosphonates and -bisphosphonates. Furthermore, the current review summarizes and comprehensively describes articles on the biological applications of hydroxyl- and amino-phosphonates and -bisphosphonates from 2015 until today.

Rh-catalyzed asymmetric hydrogenation of α- and β-enamido phosphonates: highly enantioselective access to amino phosphonic acids

Broad substrate scope; high isloated yield and enantioselectivity; novel hybrid bisphosphine ligands; gram-scale reaction with lower catalyst usage.

Copper(I)-catalysed intramolecular hydroarylation-redox cross-dehydrogenative coupling of N-propargylanilines with phosphites

Intramolecular hydroarylation-redox cross-dehydrogenative coupling of N-propargylanilines with phosphite diesters proceeded in the presence of Cu(I)-catalysts (20 mol%) to selectively give 2-phosphono-1,2,3,4-tetrahydroquinolines in good yields with 100% atomic utilization. P-H and two C-H bonds are activated at once and these hydrogen atoms are trapped by a propargylic triple bond in the molecule.

Enantioselective hydrophosphonylation of N-Boc imines using chiral guanidine-thiourea catalysts

The enantioselective hydrophosphonylation of N-Boc imines was investigated using a new family of pseudo-symmetric guanidine-thiourea catalysts, providing α-amino phosphonates in moderate to high yields with good enantioselectivity. The catalyst was heterogenized by polymerization with styrene and the resulting catalyst was applied to reactions under continuous-flow conditions.

Synthesis and potential antimicrobial activity of novel α-aminophosphonates derivatives bearing substituted quinoline or quinolone and thiazole moieties

To develop novel antimicrobial agents, and based on the biologically active heterocyclic quinoline and thiazole substituted, a series of novel α-aminophosphonates (9a–h) and (10i–l) derivatives that incorporated quinoline or quinolone, and coumarylthiazole or 5-phenylthiazol-2-amine moieties were designed and synthesized via Kabachnik–Fields reaction in the presence of ionic liquid under ultrasound irradiation. All the new compounds were obtained in good yield with a simple workup and were confirmed using various spectroscopic methods. The in vitro antimicrobial activity of all synthesized compounds were screened in terms of MIC values against the selected strains of Gram-negative and Gram-positive bacteria and two fungal strains using the broth micro-dilution method. The results showed that most of the tested compounds showed moderate inhibitory activities against both Gram‐positive and ‐negative bacteria compared with reference drugs. The following compounds 9e, 9g, 9h, 9i and 9f, 9g, 9h, 10k, 10l are the most active against Gram-positive and Gram-negative bacteria strains, respectively, with MIC values ranging between 0.25 and 128 μg/mL. The synthesized compounds 9b, 9c, 9f, 9g, 9h, 10k, and 10l exhibited excellent antifungal inhibition with MIC values ranging between 0.25 and 32 μg/mL. Structure–activity relationship revealed that the presence of coumarylthiazole moiety and hydroxyl in the quinoline group increased the inhibitory activity against microbial strains pathogens. These results confirm that the synthesized compounds can be potential antimicrobial drugs candidate.

Synthesis and potent antimicrobial activity of novel coumarylthiazole α-aminophosphonates derivatives

Herein, we reported a novel series of α-aminophosphonates derivatives (IV)a-m bearing an important pharmacophore coumarylthiazole moiety. All the new compounds have been synthesized via Kabachnik-Fields reaction under ultrasonic irradiation. The products were obtained in good yield with a simple workup and were confirmed using various spectroscopic methods. All these compounds (IV)a-m were screened for their in vitro for antimicrobial activity against thirteen Gram-negative bacteria and five Gram-positive bacteria and Candida albicans strains. The results showed that all the synthesized compounds exhibited moderate antibacterial activities against both references and multidrug-resistant and antifungal strains. The compound (IV)e showed the highest activities against all pathogens of the tested microbial strains with MIC of 0.125 μg/mL. The compounds (IV)h, (IV)f, (IV)b, and (IV)d exhibited moderate and promising activities with MIC of 0.125 μg/mL. Structure-activity relationship revealed that inhibitory activity of the synthesized compounds is related to the type of the substituted group on phenyl rings, and these results showed that the electron-donating groups at ortho and para positions have a high relationship increasing antimicrobial activities than the electron-withdrawing groups. These results confirm that coumarylthiazole α-aminophosphonates compounds can be potential antimicrobial drugs candidate.

Asymmetric Synthesis of Tetrasubstituted α-Aminophosphonic Acid Derivatives

Due to their structural similarity with natural α-amino acids, α-aminophosphonic acid derivatives are known biologically active molecules. In view of the relevance of tetrasubstituted carbons in nature and medicine and the strong dependence of the biological activity of chiral molecules into their absolute configuration, the synthesis of α-aminophosphonates bearing tetrasubstituted carbons in an asymmetric fashion has grown in interest in the past few decades. In the following lines, the existing literatures for the synthesis of optically active tetrasubstituted α-aminophosphonates are summarized, comprising diastereoselective and enantioselective approaches.

Asymmetric synthesis of organophosphorus compounds using H-P reagents derived from chiral alcohols

Chiral organophosphorus compounds, especially those containing C-stereogenic carbons in the proximity of the phosphorus atom, are known for their unique properties and have found wide applications that span from medicinal chemistry to enantioselective catalysis. However, the synthesis of such chiral molecules, especially with the precise control of stereochemistry at chiral carbon atoms, still remains a very challenging task. This review summarizes recent advances in the highly stereoselective formation of C- and, in some cases, also P-stereogenic organophosphorus compounds. The presented synthesis strategy is based on the use of H-P reagents bearing TADDOL, BINOL or a menthol moiety attached to the phosphorus atom and serving as a chiral auxiliary. Reactions of such chiral H-P species with different partners, e.g., alkenes, alkynes, imines, and carbonyl compounds, leading to structurally diverse chiral organophosphorus compounds with up to five chiral centers are comprehensively discussed. In each case, the stereochemical outcome of the reaction is influenced by the presence of the chiral alcohol used; therefore, the content of this review is compiled into sections with respect to the type of chiral alcohol attached to the phosphorus atom in the H-P species applied.

Diethyl [(4-{(9H-carbazol-9-yl)methyl}-1H-1,2,3-triazol-1-yl)(benzamido)methyl]phosphonate

The title compound, diethyl [(4-{(9H-carbazol-9-yl)methyl}-1H-1,2,3-triazol-1-yl)(benzamido)methyl]phosphonate, was synthesized with excellent yield and high regioselectivity through 1,3-dipolar cycloaddition reaction between the α-azido diethyl amino methylphosphonate and the heterocyclic alkyne, 9-(prop-2-yn-1-yl)-9H-carbazole. The cyclization reaction by “click chemistry” was carried out in a water/ethanol solvent mixture (50/50), in the presence of copper sulfate pentahydrate and catalytic sodium ascorbate. The characterization of the structure of the resulting 1,4-regioisomer was performed by 1D and 2D-NMR experiments, infrared spectroscopy, and elemental analysis.