Phosphonate Derivatives of Paracetamol and Valproic Acid.

Paracetamol and valproic acid are standalone drugs with leading position in the world drug market. The phosphonate analogues of these drugs were synthesized and were tested in vivo. N-(4-hydroxyphenylcarbamoyl)phosphonic acid was four times more potent than paracetamol in preventing acetic acid-induced writhing. Phosphonate derivative of valproic acid, (2-propylpentanoyl)phosphonic acid, had similar in vivo activity to valproic acid in the pentylenetetrazole-induced kindling mouse model.

Recent advances in the synthesis of 4'-truncated nucleoside phosphonic acid analogues.

The synthesis of five series of 4'-truncated nucleoside phosphonic acid analogues is discussed in this review: (1) 4'-truncated furanose nucleoside phosphonic acid analogues; (2) 4'-truncated pyrrolidine nucleoside phosphonic acid analogues; (3) 4'-truncated carbocyclic nucleoside phosphonic acid analogues; (4) 4'-truncated isoxazole nucleoside phosphonic acid analogues; (5) 4'-truncated miscellaneous nucleoside phosphonic acid analogues. Five different ways are used to make the phosphonate moiety: (i) Michaelis-Arbuzov reaction of RX (X = Br, I, OTf) with trialkyl phosphate; (ii) Lewis acid catalyzed Michaelis-Arbuzov reaction of glycoside with trialkyl phosphite; (iii) nucleophilic addition of a dialkyl phosphite to a carbonyl group; (iv) direct coupling reaction with amino alkyl phosphonate; (v) de novo synthesis of phosphonated-isoxazole and 1,3-dioxolane heterocycles from phosphonated starting materials. Their biological activity results are briefly discussed.

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.

Phosphonic Analogs of Alanine as Acylpeptide Hydrolase Inhibitors.

Acylpeptide hydrolase is a serine protease, which, together with prolyl oligopeptidase, dipeptidyl peptidase IV and oligopeptidase B, belongs to the prolyl oligopeptidase family. Its primary function is associated with the removal of N-acetylated amino acid residues from proteins and peptides. Although the N-acylation occurs in 50-90 % of eukaryotic proteins, the precise functions of this modification remains unclear. Recent findings have indicated that acylpeptide hydrolase participates in various events including oxidized proteins degradation, amyloid ß-peptide cleavage, and response to DNA damage. Considering the protein degradation cycle cross-talk between acylpeptide hydrolase and proteasome, inhibition of the first enzyme resulted in down-regulation of the ubiquitin-proteasome system and induction of cancer cell apoptosis. Acylpeptide hydrolase has been proposed as an interesting target for the development of new potential anticancer agents. Here, we present the synthesis of simple derivatives of (1-aminoethyl)phosphonic acid diaryl esters, phosphonic analogs of alanine diversified at the N-terminus and ester rings, as inhibitors of acylpeptide hydrolase and discuss the ability of the title compounds to induce apoptosis of U937 and MV-4-11 tumor cell lines.

Synthesis and Inhibitory Studies of Phosphonic Acid Analogues of Homophenylalanine and Phenylalanine towards Alanyl Aminopeptidases.

A library of novel phosphonic acid analogues of homophenylalanine and phenylalanine, containing fluorine and bromine atoms in the phenyl ring, have been synthesized. Their inhibitory properties against two important alanine aminopeptidases, of human (hAPN, CD13) and porcine (pAPN) origin, were evaluated. Enzymatic studies and comparison with literature data indicated the higher inhibitory potential of the homophenylalanine over phenylalanine derivatives towards both enzymes. Their inhibition constants were in the submicromolar range for hAPN and the micromolar range for pAPN, with 1-amino-3-(3-fluorophenyl) propylphosphonic acid (compound 15c) being one of the best low-molecular inhibitors of both enzymes. To the best of our knowledge, P1 homophenylalanine analogues are the most active inhibitors of the APN among phosphonic and phosphinic derivatives described in the literature. Therefore, they constitute interesting building blocks for the further design of chemically more complex inhibitors. Based on molecular modeling simulations and SAR (structure-activity relationship) analysis, the optimal architecture of enzyme-inhibitor complexes for hAPN and pAPN were determined.

Synthesis of α-Aminophosphonic Acid Derivatives Through the Addition of O- and S-Nucleophiles to 2H-Azirines and Their Antiproliferative Effect on A549 Human Lung Adenocarcinoma Cells.

This work reports a straightforward regioselective synthetic methodology to prepare α-aminophosphine oxides and phosphonates through the addition of oxygen and sulfur nucleophiles to the C-N double bond of 2H-azirine derivatives. Determined by the nature of the nucleophile, different α-aminophosphorus compounds may be obtained. For instance, aliphatic alcohols such as methanol or ethanol afford α-aminophosphine oxide and phosphonate acetals after N-C3 ring opening of the intermediate aziridine. However, addition of 2,2,2-trifluoroethanol, phenols, substituted benzenthiols or ethanethiol to 2H-azirine phosphine oxides or phosphonates yields allylic α-aminophosphine oxides and phosphonates in good to high general yields. In some cases, the intermediate aziridine attained by the nucleophilic addition of O- or S-nucleophiles to the starting 2H-azirine may be isolated and characterized before ring opening. Additionally, the cytotoxic effect on cell lines derived from human lung adenocarcinoma (A549) and non-malignant cells (MCR-5) was also screened. Some α-aminophosphorus derivatives exhibited very good activity against the A549 cell line in vitro. Furthermore, selectivity towards cancer cell (A549) over non-malignant cells (MCR-5) has been detected in almost all compounds tested.

Phosphonic Acid Analogs of Fluorophenylalanines as Inhibitors of Human and Porcine Aminopeptidases N: Validation of the Importance of the Substitution of the Aromatic Ring.

A library of phosphonic acid analogs of phenylalanine substituted with fluorine, chlorine and trifluoromethyl moieties on the aromatic ring was synthesized and evaluated for inhibitory activity against human (hAPN) and porcine (pAPN) aminopeptidases. Fluorogenic screening indicated that these analogs are micromolar or submicromolar inhibitors, both enzymes being more active against hAPN. In order to better understand the mode of the action of the most active compounds, molecular modeling was used. It confirmed that aminophosphonic portion of the enzyme is bound nearly identically in the case of all the studied compounds, whereas the difference in activity results from the placement of aromatic side chain of an inhibitor. Interestingly, both enantiomers of the individual compounds are usually bound quite similarly.

Radiation Safety Considerations in the Treatment of Canine Skeletal Conditions Using 153Sm, 90Y, and 117mSn.

The treatment of pets, service animals, and pre-clinical research subjects with radionuclides raises concern for the safety of the people who interact with the animals after their treatment. Three treatments of skeletal conditions in dogs are considered in this study: Sm-1,4,7,10-tetraazacylcododecanetetramethylenephosphonic acid, which is a bone-seeking radiopharmaceutical; unencapsulated Y permanent interstitial implants, which are sometimes called "liquid brachytherapy"; and Sn radiosynoviorthesis, which is also called radiosynovectomy. External exposure rate readings of the Sm and Sn treatments, and Monte Carlo simulations of Sn at a distance of 1 m and of all three in direct contact with tissue were analyzed for doses. Dogs that have received any of these treatments using typically administered activities may be released from radiation safety isolation immediately after treatment from the standpoint of external exposure. People should avoid prolonged close proximity, such as sleeping with a treated dog, for three weeks following an Y interstitial implant or for a month following Sn radiosynoviorthesis. No such avoidance is necessary after treatment with Sm-1,4,7,10-tetraazacylcododecanetetramethylenephosphonic acid.

Novel triorganotin complexes based on phosphonic acid ligands: Syntheses, structures and in vitro cytostatic activity.

Six novel organotin phosphonate complexes, [(Me3Sn)4(HL1)4]n1, [(Me3Sn)2(HL2)2]n2, [(Me3Sn)2L3(H2O)]n3, [(Ph3Sn)(HL1)]64, [(Ph3Sn)2L2]n5 and [(Ph3Sn)2L3]66, derived from phosphonic acid ligands [NaHL1 = 1-C10H7OPO2(OH)Na, H2L2 = 1-C10H7PO(OH)2, H2L3 = 2-C10H7PO(OH)2], have been synthesized and characterized by elemental analysis, FT-IR, NMR (1H, 13C, 31P and 119Sn) spectroscopy and X-ray crystallography. The structural analysis reveals that complexes 1 and 5 display 1D infinite zig-zag chain structures, and complex 2 shows 1D right-handed helical chain structure, while complex 3 displays 1D left-handed helical chain structure. Complexes 4 and 6 are 24-membered macrocyclic rings interconnected by P, O and Sn atoms. Additionally, the molecules of complexes 1 and 3 are further linked through intermolecular π···π and O-H···O interaction into supramolecular structures, respectively. Furthermore, we preliminarily estimated in vitro cytostatic activity of complexes 1-6 against the human cervix tumor cells (HeLa), human hepatocellular carcinoma cells (HepG-2) and human normal breast cells (HBL-100). Importantly, the anti-proliferative properties and possible pathway of complex 6 are investigated, and the results demonstrate that complex 6 could induce apoptotic cell death via an overload of intracellular reactive oxygen species (ROS) levels and the dysfunctional depolarization of mitochondrial membranes.

Rational design of some substituted phenyl azanediyl (bis) methylene phosphonic acid derivatives as potential anticancer agents and imaging probes: Computational inputs, chemical synthesis, radiolabeling, biodistribution and gamma scintigraphy.

Bisphosphonates are widely used for treatment of osteoporosis. Recently, they have been reported to be effective anticancer agents. In this work, we designed some substituted phenyl (azanediyl) bis (methylene phosphonic acid) to be tested for their anticancer effect. Both molecular docking and dynamics studies were used to select the top ranked highly scored compounds. The selected hits showed potential in vitro anticancer effect against some cell lines. Biodistribution pattern and gamma scintigraphy were conducted to the most effective derivative (BMBP) after radiolabeling with 99mTc. Results of biodistribution and scintigraphic imaging of 99mTc-BMBP in tumor bearing mice showed a notable tumor affinity, and confirmed the targeting affinity of BMBP to the tumor tissues. As a conclusion, BMBP could act as potential anticancer agent and imaging probe.

Synthesis, Characterization and Evaluation of Cytotoxic Activities of Novel Aziridinyl Phosphonic Acid Derivatives.

New aziridine 2-phosphonic acids were prepared by monohydrolysis of the aziridine 2-phosphonates that were obtained by the modified Gabriel-Cromwell reaction of vinyl phosphonate or α-tosylvinyl phosphonate with a primary amine or a chiral amine. The cellular cytotoxicity of these compounds was tested against the HCT-116 colorectal cancer cell lines and the CCD-18Co normal colon fibroblast lines using the MTT assay. Three of the synthesized phosphonic acid derivatives 2e (ethyl hydrogen {(2S)-1-[(1S)-1-(naphthalen-2-yl)ethyl]aziridin-2-yl}phosphonate), 2h (ethyl hydrogen (1-benzylaziridin-2-yl)phosphonate), and 2i (ethyl hydrogen (1-cyclohexylaziridin-2-yl)phosphonate) showed higher cytotoxicity than the reference cancer treatment agent etoposide. Cell death was through a robust induction of apoptosis even more effectively than etoposide, a well-known apoptosis inducing agent.

Phosphonic and Phosphinic Acid Derivatives as Novel Tyrosinase Inhibitors: Kinetic Studies and Molecular Docking.

A dozen of phosphonic and phosphinic acid derivatives containing pyridine moiety were synthesized and its inhibitory activity toward mushroom tyrosinase was investigated. Moreover, molecular docking of these compounds to the active site of the enzyme was performed. All the compounds (1-10) demonstrated the inhibitory effect with the IC50 and inhibition constants ranging millimolar concentrations. The obtained results indicate that the compounds show different types of inhibition (competitive, noncompetitive, mixed), but all of them are reversible inhibitors. The obtained outcomes allowed to make the structure-activity relationship (SAR) analysis. Compound 4 ([(benzylamino)(pyridin-2-yl)methyl]phenylphosphinic acid) revealed the lowest IC50 value of 0.3 mm and inhibitory constant of Ki 0.076 mm, with noncompetitive type and reversible mechanism of inhibition. According to SAR analysis, introducing bulky phenyl moieties to phosphonic and amino groups plays an important role in the inhibitory potency on activity of mushroom tyrosinase and could be useful in design and development of a new class of potent organophosphorus inhibitors of tyrosinase. Combined results of molecular docking and SAR analysis can be helpful in designing novel tyrosinase inhibitors of desired properties. They may have broad application in food industry and cosmetology.

Structural exploration of cinnamate-based phosphonic acids as inhibitors of bacterial ureases.

The conjugated system of cinnamic acid, α-substituted with a phosphonoalkyl residue, was previously validated as a scaffold that provided one of the most potent organophosphorus inhibitors of bacterial urease. Following the idea of using Morita-Baylis-Hillman adducts to introduce the terminal phosphonic side chain functionality to the α,ß-unsaturated system, we currently report the synthesis and activity of an extended series of compounds. Cinnamates modified with 3-phosphonopropyl and 4-phosphonobutyl side chains were obtained in a convenient two-step procedure, which involved Pd-mediated transformations of the Morita-Baylis-Hillman bromides as the key substrates. The introduction of a terminal alkenyl fragment, which was achieved by Stille coupling with stannanes, was followed by a tandem C-P bond formation/oxidation process. A submicromolar ligand of Sporosarcina pasteurii urease (Ki = 0.509 µM) was identified among the active molecules. In addition, inhibitors of Proteus mirabilis urease affected bacterial growth at the micromolar level. Based on the structure-activity relationship and the mechanism of inhibition, we suggest a nontypical mixed mode of action for the slow binding compounds. We presume that the molecular distance between the phosphonic group and the backbone double bond allows a dual activity: complexation of the acidic group with nickel ions and Michael addition of a cysteine forming the active site lid.

Multiple-step, one-pot synthesis of 2-substituted-3-phosphono-1-thia-4-aza-2-cyclohexene-5-carboxylates and their corresponding ethyl esters.

The multiple-step, one-pot procedure for a series of 2-substituted-3-phosphono-1-thia-4-aza-2-cyclohexene-5-carboxylates, analogues of the natural, sulfur amino acid metabolite lanthionine ketimine (LK), its 5-ethyl ester (LKE) and 2-substituted LKEs is described. Initiating the synthesis with the Michaelis-Arbuzov preparation of α-ketophosphonates allows for a wide range of functional variation at the 2-position of the products. Nine new compounds were synthesized with overall yields range from 40 to 62%. In addition, the newly prepared 2-isopropyl-LK-P, 2-n-hexyl-LKE-P and 2-ethyl-LKE were shown to stimulate autophagy in cultured cells better than that of the parent compound, LKE.

Suppressive effects of tenofovir disoproxil fumarate, an antiretroviral prodrug, on mineralization and type II and type III sodium-dependent phosphate transporters expression in primary human osteoblasts.

Tenofovir disoproxil fumarate (TDF) is an antiretroviral drug commonly used for the management of Human Immunodeficiency Virus (HIV) in highly active antiretroviral therapy (HAART) and of chronic Hepatitis B Virus (HBV) infections. Long-term TDF-treated subjects present decrease of bone mineral density and rarely severe osteomalacia. Although these adverse effects have been attributed to the impaired proximal tubule function, a possible direct involvement of TDF on osteoblasts should be taken into account. The aim of this study was to evaluate whether sodium phosphate transporters NPT2A (sodium-dependent phosphate transport protein 2A), NPT2C (sodium-dependent phosphate transport protein 2C), PIT1 (sodium-dependent phosphate transporter 1), and PIT2 (sodium-dependent phosphate transporter 2) were expressed in primary human osteoblasts (HOBs), whether their expression was related to HOBs differentiation and whether TDF could affect mineralization and gene expression. PIT1 and PIT2 were expressed under proliferating conditions and increased after induction of mineralization, while NPT2A and NPT2C were almost undetectable. In HOBs TDF exposure induced a significant dose-dependent decrease in mineralization. Moreover, TDF caused a reduction of COL1A1 and of ATF4 expression in differentiated HOBs. In summary, HOBs do not express NPT2A and NPT2C and do express PIT1 and PIT2, suggesting a role of these two latter in human osteoblast mineralization. TDF impairs osteoblast mineralization, confirming a direct negative effect on bone. Therefore, in clinical practice, bone damage must be suspected and evaluated also in patients receiving TDF without kidney function alterations.

Study of influence of 1,3-oxazole-4-yl-phosphonic acid derivative on nitric oxide system indicators in rats with arterial hypertension.

Arterial hypertension is a leader among the most common chronic cardiovascular diseases which covers 30-45% of world population with a dynamics of further growth. 1,3-oxazole-4-yl-phosphonic acid derivative (abbreviated as oxazole derivative) is a novel original compound with vasodilating activity. The purpose of this work was to study the NO-mediated mechanism of vasodilating effect of this derivative according to the activity of eNOS, iNOS and NO2- through their content in rats on a resistant arterial hypertension model. The oxazole derivative intraperitoneally administered at a dose of 25 mg/kg prevented development of arterial hypertension by promotion of recovery of eNOS, iNOS and NO2- activity in the studied aorta, heart, and blood serum to the normal level recorded in intact animals. It can be concluded that the mechanism of antihypertensive action of the oxazole derivative is mediated by the NO system. Key words: arterial hypertension nitric oxide 1,3-oxazole-4-yl-phosphonic acid derivative.

Dual targeting of cancer-related human matrix metalloproteinases and carbonic anhydrases by chiral N-(biarylsulfonyl)-phosphonic acids.

A series of nanomolar phosphonate matrix metalloproteinase (MPP) inhibitors was tested for inhibitory activity against a panel of selected human carbonic anhydrase (CA, EC 4.2.1.1) isozymes, covering the cancer-associated CA IX and XII. None of the reported sulfonyl and sulfonylamino-derivatives sensitively affected the catalytic activity of the cytosolic isoforms CA I and II, which are considered off-target isoforms in view of their physiological role. The most active inhibitors were in the series of chiral N-(sulfonyl)phosphovaline derivatives, which showed good to excellent inhibitory activity over target CAs, with compound 15 presenting the best isoform-selectivity toward CA IX. We suggest here that the phosphonates have the potential as dual inhibitors of MMPs and CAs, both involved in tumor formation, invasion and metastasis.

Combinatorial and sequential delivery of gemcitabine and oseltamivir phosphate from implantable poly(d,l-lactic-co-glycolic acid) cylinders disables human pancreatic cancer cell survival.

Combination therapies against multiple targets are currently being developed to prevent resistance to a single chemotherapeutic agent and to extirpate pre-existing resistance in heterogeneous cancer cells in tumors due to selective pressure from the single agent. Gemcitabine (GEM), a chemotherapeutic agent, is the current standard of care for patients with pancreatic cancer. Patients with pancreatic cancer receiving GEM have a low progression-free survival. Given the poor response rate to GEM, cancer cells are known to develop rapid resistance to this drug. Metronomic chemotherapy using combinatorial and sequential delivery systems are novel developmental approaches to disrupt tumor neovascularization, reduce systemic drug toxicity, and increase the sensitivity of chemotherapeutics in cancer. Here, implantable double-layered poly(d,l-lactic-co-glycolic acid) (PLGA) cylinders were engineered to sequentially release GEM in combination with oseltamivir phosphate (OP) over an extended time. Double-layered PLGA cylindrical implants loaded with these active hydrophilic drugs were fabricated with minimal loss of drugs during the formulation, enabling extensive control of drug loading and establishing uniform drug distribution throughout the polymer matrix. OP is used in the formulation because of its anticancer drug properties targeting mammalian neuraminidase 1 (Neu1) involved in multistage tumorigenesis. OP and GEM encapsulated in inner/outer GEMin/OPout or OPin/GEMout implantable double-layered PLGA cylinders displayed sustained near linear release over 30 days. OP and GEM released from the double-layered PLGA cylinders effectively reduced cell viability in pancreatic cancer cell line PANC1 and its GEM-resistant variant for up to 15 days.

1-Aminobenzocyclobutene-1-phosphonic Acid and Related Compounds as Inhibitors of Phenylalanine Ammonia-Lyase.

Five new geminal aminocycloalkanephosphonic acids (4 - 8) containing both an aromatic ring and a cycloalkane ring were synthesized and evaluated as potential inhibitors of buckwheat phenylalanine ammonia-lyase (PAL). Within the set of compounds which are related to 2-aminoindane-2-phosphonic acid (AIP, 3), a known powerful inhibitor of PAL, racemic 1-aminobenzocyclobutene-1-phosphonic acid (4), was six times weaker than AIP as an in vitro inhibitor of buckwheat PAL, but six times stronger than AIP as an in vivo inhibitor of phenylalanine-derived anthocyanin synthesis in buckwheat.

Anticancer activity of new molecular hybrids combining 1,4-naphthalenedione motif with phosphonic acid moiety in hepatocellular carcinoma HepG2 cells.

Structural motifs found in naturally occurring compounds are frequently used by researchers to develop novel synthetic drug candidates. Some of these new agents are hybrid molecules which are designed through a concept of combining more than one functional element. In this report, anticancer activity of new synthetic molecular hybrids, substituted 3-diethoxyphosphorylnaphtho[2,3-b]furan-4,9-diones and 3-diethoxyphosphorylbenzo[f]indole-4,9-diones, which integrate natural 1,4-naphtalenedione scaffold, present in several anticancer agents, with pharmacophoric phosphonate moiety, were tested against hepatocellular cell line HepG2. Cytotoxicity was examined using MTT assay. Two most potent compounds, furandione 8a and benzoindoldione 12a, which reduced the number of viable HepG2 cells with the IC50 values of 4.13 µM and 5.9 µM, respectively, were selected for further research. These compounds decreased the mRNA expression levels of several genes: Bcl-2, angiogenic vascular endothelial growth factor (VEGF), c-Fos, caspase-8 and increased the expression of Bax, caspase-3 and -9, c-Jun, p21, p53, as determined by quantitative real-time PCR. The ability of these compounds to induce apoptosis and DNA damage was studied by flow cytometry. The obtained data showed that the new compounds inhibited cell viability by increasing apoptosis and decreasing angiogenesis. Compound 8a was a much stronger apoptosis inducer as compared with 12a and strongly activated the intrinsic pathway of apoptosis, associated with the loss of mitochondrial membrane potential and changes in Bax/Bcl-2 ratio. These findings show that the synthetic hybrids combining 1,4-naphthalenedione system and phosphonic acid moiety display potential to be further explored in the development of new anticancer agents.