Iminodiacetic Acid as a Novel Metal-Binding Pharmacophore for New Delhi Metallo-ß-lactamase Inhibitor Development.

The fungal natural product aspergillomarasmine A (AMA) has been identified as a noncompetitive inhibitor of New Delhi metallo-ß-lactamase-1 (NDM-1) that inhibits by removing ZnII from the active-site. The nonselective metal-chelating properties and difficult synthesis and derivatization of AMA have hindered the development of this scaffold into a potent and selective inhibitor of NDM-1. Iminodiacetic acid (IDA) has been identified as the metal-binding pharmacophore (MBP) core of AMA that can be leveraged for inhibitor development. Herein, we report the use of IDA for fragment-based drug discovery (FBDD) of NDM-1 inhibitors. IDA (IC50 =120 µM) was developed into inhibitor 23 f (IC50 =8.6 µM, Ki =2.6 µM), which formed a ternary complex with NDM-1, as evidenced by protein thermal-shift and native-state electrospray ionization mass spectrometry (ESI-MS) experiments. Combining mechanistic analysis with inhibitor derivatization, the use of IDA as an alternative AMA scaffold for NDM-1 inhibitor development is detailed.

Total synthesis of exigurin: the Ugi reaction in a hypothetical biosynthesis of natural products.

The first total synthesis of a marine natural product, exigurin, has been accomplished in 13 steps starting from (+)-menthone. The key intermediate (-)-10-epi-axisonitrile-3 was prepared by stereoselective intramolecular cyclopropanation followed by a cyclopropane ring opening reaction by the azide anion. The bioinspired Ugi reaction of (-)-10-epi-axisonitrile-3, formaldehyde, sarcosine and methanol successfully constructed the target exigurin in which its terpene and amino acid units were linked through an amide bond.

Synthesis and bioevaluation of technetium-99 m / rhenium labeled phenylquinoxaline derivatives as Tau imaging probes.

Based on our previous research on the fluorinated phenylquinoxaline scaffold, in this study, different positions of N,N-dimethyl amino group, and alkyl linkers with various lengths were introduced into this scaffold to regulate their lipophilicity and binding affinity to Tau. Four novel 99mTc/Re complexes with diethyl iminodiacetate chelator were synthesized and evaluated as Tau imaging tracers in the brain of Alzheimer's disease. Their specific binding to neurofibrillary tangles was verified by in vitro fluorescence staining and further confirmed by the results of immunofluorescence staining on the same brain sections from AD patient and Tg-tau mice. From in vitro binding assay using recombinant Tau aggregates, complex 4.2 with 6-N(CH3)2 and longer carbon chain (n = 4) displayed the highest affinity (Kd = 59.95 nM). [99mTc]4.2 was achieved by the ligand exchange reaction between dicarboxylic precursor and [99mTc(CO)3(H2O)3]+ intermediate with radiochemical yield over 45%. Ex vivo biodistribution studies on normal ICR mice revealed that [99mTc]4.2 exhibited moderate initial brain uptake (0.61% ID/g) and more structure optimizations are still required to improve the blood-brain barrier permeability.

Synthesis and Biocompatibility Studies of New Iminodiacetic Acid Derivatives.

BACKGROUND: Iminodiacetic acid (IDA) derivatives can be used as ligands to form complexes with technetium, with potential application as hepatobiliary diagnostic agents. The aim of this study was to synthesize five novel IDA derivatives and to compare their effects on plasma haemostasis with clinically approved ligands for technetium complexation. METHODS: The influence of synthesized IDA derivatives on plasma haemostasis was evaluated spectrophotometrically by clot formation and lysis test (CL-test), coagulation assay, Prothrombin Time and Activated Partial Tromboplastin Time. The effects of the tested compounds on erythrocytes were assessed using haemolysis assays, microscopy and flow cytometry studies. RESULTS: Despite their significant influence on the kinetic parameters of the process of clot formation and fibrinolysis, the tested ligands, at potential diagnostic concentrations, did not alter the overall potential of clot formation and lysis (CLAUC). At potential diagnostic concentrations (0.4 µmol/mL) all the tested compounds showed no adverse effects on the membranes of RBCs (Red Blood Cells). CONCLUSION: IDA derivatives with methoxy substituents in aromatic ring, exert multidirectional effects on plasma haemostasis and should be considered safe as their significant impacts were mostly observed at 4 µmol/mL, which is about 10-fold higher than the theoretical plasma concentrations of these compounds.

Stability of erythrocyte membrane and overall hemostasis potential - A biocompatibility study of mebrofenin and other iminodiacetic acid derivatives.

BACKGROUND: Intravenous injection seems to be the most convenient way of administering drugs and contrast agents, which makes components of the blood the first and usually unwanted target of their action. Binding of intravenously administered compounds to erythrocytes, blood platelets and vascular wall may have serious clinical implications. The aim of this study was to examine the influence of four iminodiacetic acid derivatives, potential ligands for gadolinium complexation, on the process of coagulation and fibrinolysis, activity of thrombin and hemolysis. METHODS: Kinetic parameters of coagulation and fibrinolysis process were determined during an optical CL-test based on measurement of transmittance alterations. Thrombin (0.5 IU/mL) and t-PA (240 ng/mL) were used to obtain a clotting and lysis curve. The activity of thrombin was determined with a chromogenic substrate S-2238. Hemolysis was examined spectrophotometrically and expressed as a percentage of released hemoglobin. RESULTS: Exposure to iminodiacetic acid derivatives resulted in a significant increase in the overall potential of clotting and lysis (CLAUC), as well as with the significant changes in the key parameters of these processes (thrombin time, initial plasma clotting velocity, clot stabilization time). Furthermore, iminodiacetic acid derivatives caused a significant decrease in the amidolytic activity of thrombin and enhanced hemolysis in a concentration-dependent manner. CONCLUSION: Despite their influence on the process of coagulation and fibrinolysis, amidolytic activity of thrombin and hemolysis, iminodiacetic acid derivatives should be generally considered safe as the significant effects were observed mostly at 4 µmol/mL, which is about 10-fold higher than the theoretical plasma concentration of these compounds.

Iminodiacetic acid functionalized porous hydroxyapatite nanoparticles for capturing histidine-tagged proteins.

A simple strategy has been developed to synthesize hydroxyapatite (HAP) nanoparticles (NPs) in a simulated body fluid (SBF). The HAP NPs have an average diameter of 50nm and present porous structure. By taking advantage of surface hydroxyl groups, the HAP NPs are further modified with iminodiacetic acid (IDA), followed by chelating Ni(2+) ions. The HAP/IDA-Ni(2+) NPs as novel adsorbent can capture directly histidine-tagged (His-tagged) proteins from the mixture of lysed cells without sample pretreatment. Results indicated that the HAP/IDA-Ni(2+) NPs present negligible nonspecific adsorption and high protein binding ability, and their specificity and affinity toward His-tagged proteins can remain after 5 times of recycling. The HAP/IDA-Ni(2+) NPs are especially suitable for purification of His-tagged proteins with low molecule weight.

Synthesis, spectroscopy, and binding constants of ketocatechol-containing iminodiacetic acid and its Fe(III), Cu(II), and Zn(II) complexes and reaction of Cu(II) complex with H2O2 in aqueous solution.

A new neuromelanin-like ketocatechol-containing iminodiacetic acid ligand, (N-(3,4-dihydroxyl)phenacylimino)diacetic acid (H4L), which is also quite similar to compounds found in insect cuticle, has been synthesized and characterized. The X-ray crystal structure of H4L has been successfully determined. Proton binding and coordination with Fe(III), Cu(II), and Zn(II) have been studied by potentiometric titrations and UV-vis spectrophotometry in aqueous solution. UV spectra of H4L in the absence and presence of different metal ions indicate complexes formed with the catechol moiety of H4L in aqueous solution. Visible spectra and NMR reveal that H4L with Fe(III), Cu(II), and Zn(II) can all give stable mono-(ML) and dinuclear complexes [M(ML)]. Fe(III) can also form {Fe(FeL)2} and {Fe(FeL)3} species with sufficient base. The process is accompanied by a drastic color change from light blue to deep-blue to wine-red. The Fe(III)-Cu(II) heteronuclear complex also exists in aqueous solution whose spectra are similar to the homonuclear Fe(III) complex. However, the spectra of {Fe(CuL)} shifted to a longer wavelength and {Fe(CuL)2} and {Fe(CuL)3} shifted to a shorter wavelength. Keto-enol tautomerism was observed in weak basic aqueous solution as indicated by (1)H NMR spectra. The reaction products of Cu(II) complex with H2O2 depend on the H2O2 concentration and pH value. Low concentrations of H2O2 oxidize H4L to a series of semiquinone and quinone compounds with absorption maxima at 314-400 nm, while a high concentration of H2O2 oxidizes H4L to colorless muconic acid derivatives. NaIO4 gives different oxidase products, but no 2,4,5-trihydroxyphenylalanine quinone (TPQ)-like hydroxyquinone can be found.

Regioselective tandem N-alkylation/C-acylation of ß,γ-alkynyl α-imino esters.

A new synthesis of α-quaternary alkynyl amino esters and allenoates was developed utilizing umpolung N-addition to ß,γ-alkynyl α-imino esters followed by regioselective acylation. The reaction exhibits broad substrate generality and unique regioselectivity. Moreover, synthesis of α-quaternary alkynyl amino esters was also carried out via oxidation of the intermediary enolate followed by alkylation.

Bone selective protective effect of a novel bone-seeking estrogen on trabecular bone in ovariectomized rats.

The drawbacks of estrogen restrict the clinical use of hormone replacement therapy, and it would be most helpful to explore new estrogenic substances that could prevent bone loss and be free from any adverse effects. We synthesized a new compound named bone-seeking estrogen (SE2) by combining 17ß-estradiol (E2) with iminodiacetic acid through the Mannich reaction. E2 and SE2 were labeled with isotope (3)H, and the tissue distribution tests of E2-(3)H and SE2-(3)H were analyzed by the radioactivity. The specific nuclear binding of E2 and SE2 in osteoblasts was measured. SE2 exhibited significantly greater affinity for bone but lower affinity for ovary and uterus than did E2, and SE2 maintained a high affinity for the estrogen receptor alpha similar to that of E2. SE2 administration did not induce uterine hypertrophy. Body weight increase was significantly suppressed by treatment with E2 but not by SE2 after ovariectomy (OVX). SE2 decreased bone turnover as E2 after OVX detected by serum biochemical markers. Bone histology and micro-CT analysis revealed that SE2 administration, similar to E2, could improve bone mass and trabecular architecture after OVX. Biomechanical analyses showed that SE2 treatment effectively increased mechanical properties after OVX. The results suggested that SE2 was effective in preventing OVX-induced bone loss and exhibited few side effects on body weight and uterine hypertrophy, which was beneficial in reducing the adverse effects caused by E2. SE2 may be a better choice than E2 for the prevention of postmenopausal osteoporosis.

In vitro characterization of magnetic electrospun IDA-grafted chitosan nanofiber composite for hyperthermic tumor cell treatment.

Magnetic nanoparticles were the thermoseeds under an alternating magnetic field and can be used to produce highly localized hyperthermia effect on deep-seated tumor. Nevertheless, effective and precisive delivery of nanoparticles to the treatment-intended site remains a challenge. In this study, Fe3O4 nanoparticles were incorporated onto the crosslinked electrospun chitosan nanofibers using chemical co-precipitation from the Fe ions adsorbed. Such magnetic nanoparticle-nanofiber composites could be delivered to the treatment site precisely by surgical or endoscopic method. Iminodiacetic acid (IDA) functionality was grafted onto the chitosan with an aim to increase the amount of magnetic nanoparticles formed in the electrospun magnetic nanofiber composite. The morphology, crystalline phase as well as the magnetism characteristic of the magnetic electrospun nanofiber matrixes, was analyzed. Results have indicated that, with the incorporation of IDA functionality, more magnetic nanoparticles were formed in the electrospun chitosan nanofiber matrix. In addition, the magnetic IDA-grafted chitosan nanofiber composite can effectively reduced the tumor cell proliferation under the application of magnetic field. This finding suggested the magnetic electrospun chitosan nanofiber composite can be of potential for hyperthermia treatment.

Mn-citrate and Mn-HIDA: intermediate-affinity chelates for manganese-enhanced MRI.

In this study we investigated two manganese chelates in order to improve the image enhancement of manganese-enhanced MRI and decrease the toxicity of free manganese ions. Since both MnCl2 and a low-affinity chelate were associated with a slow continuous decrease of cardiac functions, we investigated intermediate-affinity chelates: manganese N-(2-hydroxyethyl)iminodiacetic acid (Mn-HIDA) and Mn-citrate. The T1 relaxivity values for Mn-citrate (4.4 m m⁻¹ s⁻¹) and Mn-HIDA (3.3 m m⁻¹ s⁻¹) in artificial cerebrospinal fluid (CSF) were almost constant in a concentration range from 0.5 to 5 m m at 37 °C and 4.7 T. In human plasma, the relaxivity values increased when the concentrations of these Mn chelates were decreased, suggesting the presence of free Mn²âº bound with serum albumin. Mn-HIDA and Mn-citrate demonstrated a tendency for better contractility when employed with an isolated perfused frog heart, compared with MnCl2. Only minimal changes were demonstrated after a venous infusion of 100 m m Mn-citrate or Mn-HIDA (8.3 µmol kg⁻¹ min⁻¹) in rats and a constant heart rate, arterial pressure and sympathetic nerve activity were maintained, even after breaking the blood-brain barrier (BBB). Mn-citrate and Mn-HIDA could not cross the intact BBB and appeared in the CSF, and then diffused into the brain parenchyma through the ependymal layer. The responses in the supraoptic nucleus induced by the hypertonic stimulation were detectable. Therefore, Mn-citrate and Mn-HIDA appear to be better choices for maintaining the vital conditions of experimental animals, and they may improve the reproducibility of manganese-enhanced MRI of the small nuclei in the hypothalamus and thalamus.

Mechanistic studies into amine-mediated electrophilic arene borylation and its application in MIDA boronate synthesis.

Direct electrophilic borylation using Y(2)BCl (Y(2) = Cl(2) or o-catecholato) with equimolar AlCl(3) and a tertiary amine has been applied to a wide range of arenes and heteroarenes. In situ functionalization of the ArBCl(2) products is possible with TMS(2)MIDA, to afford bench-stable and easily isolable MIDA-boronates in moderate to good yields. According to a combined experimental and computational study, the borylation of activated arenes at 20 °C proceeds through an S(E)Ar mechanism with borenium cations, [Y(2)B(amine)](+), the key electrophiles. For catecholato-borocations, two amine dependent reaction pathways were identified: (i) With [CatB(NEt(3))](+), an additional base is necessary to accomplish rapid borylation by deprotonation of the borylated arenium cation (σ complex), which otherwise would rather decompose to the starting materials than liberate the free amine to effect deprotonation. Apart from amines, the additional base may also be the arene itself when it is sufficiently basic (e.g., N-Me-indole). (ii) When the amine component of the borocation is less nucleophilic (e.g., 2,6-lutidine), no additional base is required due to more facile amine dissociation from the boron center in the borylated arenium cation intermediate. Borenium cations do not borylate poorly activated arenes (e.g., toluene) even at high temperatures; instead, the key electrophile in this case involves the product from interaction of AlCl(3) with Y(2)BCl. When an extremely bulky amine is used, borylation again does not proceed via a borenium cation; instead, a number of mechanisms are feasible including via a boron electrophile generated by coordination of AlCl(3) to Y(2)BCl, or by initial (heteroarene)AlCl(3) adduct formation followed by deprotonation and transmetalation.

Preparation of 99mTc(CO)3-Carboxymethylthioethyl iminodiacetic acid and evaluation as a potential renal imaging agent.

UNLABELLED: The ligand, carboxymethylthioethyl iminodiacetic acid (CMT-IDA) has a suitable array of donor atoms for coordination with [99mTc(CO)3]+ core, wherein the resultant complex is expected to possess free carboxylic residues contributing towards hydrophilicity of the complex. The aim of the studies was to study the renal clearance of 99mTc(CO)3- labeled CMT-IDA and determine the potential of the complex towards its use as a renal tubular imaging agent. METHODS: CMT-IDA was radiolabeled with the [99mTc(CO)3(H2O)3]+ precursor and was characterized by reverse phase HPLC gradient elution system. Stability, hydrophilicity and plasma protein binding studies were carried out for the complex. Biodistribution studies were carried out in normal male Swiss mice at 10 min.p.i. and 2 h.p.i. The clearance was estimated from the activity observed in the urinary bladder by tying the urethra prior to injection of the complexes under study. Imaging studies were performed with male Swiss mice administered with [99mTc(CO)3(CMT-IDA)]-2 at 30 min. p.i. and blocking studies were carried out by intraperitoneal injection of probenecid 10 min. prior to the injection of the radiotracer. RESULTS: [99mTc(CO)3(CMT-IDA)]-2 could be obtained in > 98% radiochemical purity. The complex showed renal clearance of 71.0� 5.9% ID at 10 min.p.i. which increased to 84.1� 10.6% ID at 2 h.p.i., with no major activity in blood, liver, heart, lungs, stomach and spleen. However, the intestinal uptake was high (10.3� 2.0% ID) at 2 h.p.i. Scintigraphic image of the animal injected with probenecid showed an increase in the activity in kidneys indicating excretion of the [99mTc(CO)3(CMT-IDA)]-2 complex via tubular pathway. CONCLUSION: The complex, [99mTc(CO)3(CMT-IDA)]-2 has shown excellent renal clearance and thereby can be explored further for potential use as an agent towards assessing effective renal plasma flow.

One-step coating of silica capillaries for selective protein retention by Cu(II)-IDA IMAC.

A simple protocol to obtain Cu(II)-IDA (iminodiacetic acid)-modified capillaries was developed for immobilized metal ion affinity chromatography (IMAC). It consisted in the synthesis of IDA-silane used for a one-step coating of fused silica capillaries. The approach prevented the hydrolysis of silica potentially induced by two step coatings (γ-GPTMS, then IDA) employed in the conventional method of bonding iminodiacetic acid. The IDA content was quantified using a model relating the electroosmotic flow generated in IDA-modified capillaries to the charges induced by IDA species. The retention behavior of holotransferrin and bovine serum albumin on these IMAC columns was then investigated. Holotransferrin revealed a high affinity for Cu(II)-supports through a specific interaction with Cu(II) ions whereas albumin did not show any retention. The use of such columns for sample pretreatment before an HPLC analysis was proved to be successful.

Pinene-derived iminodiacetic acid (PIDA): a powerful ligand for stereoselective synthesis and iterative cross-coupling of C(sp3) boronate building blocks.

Efficient access to chiral C(sp(3)) boronates in stereochemically pure form is critical for realizing the substantial potential of such building blocks in complex-molecule synthesis. We herein report that a pinene-derived iminodiacetic acid (PIDA) ligand enables the highly diastereoselective synthesis of a wide range of oxiranyl C(sp(3)) boronates from the corresponding olefins. These oxiranyl PIDA boronates, in turn, can be readily transformed into unprecedented stable α-boryl aldehydes via a novel 1,2-migration of the boronate group that proceeds with complete maintenance of stereochemical purity. B-Protected haloboronic acids containing dual sp(3)-hybridized C centers are readily accessible via this platform, and the herein demonstrated capacity for stereocontrolled iterative C(sp(3)) cross-coupling with this novel type of bifunctional reagent to access a medicinally important chiral small-molecule target in highly enantioenriched form represents a substantial advance for the building-block-based approach to synthesis.

A novel synthesis of iminodiacetic acid: biocatalysis by whole Alcaligenes faecalis ZJB-09133 cells from iminodiacetonitrile.

Iminodiacetic acid (IDA) has been widely used as an important intermediate in the fine chemical industry. In this study, a novel synthesis route of IDA from iminodiacetonitrile by whole microorganisms was investigated. A strain with the capability of producing nitrilase, ZJB-09133, was isolated and identified, and later named Alcaligenes faecalis ZJB-09133. In addition, the detailed biocatalysis of iminodiacetonitrile to produce IDA using ZJB-09133 was investigated. The results showed that the conversion reached 65.3% in Na(2)HPO(4)-NaH(2)PO(4) buffer of pH 8.0 under the following conditions: cells in the amount of 0.075-g DCW/L, 1.5% substrate, conversion time of 8 h, and a reaction temperature of 35°C. To the best of our knowledge, this is the first time that the production of IDA using a biocatalysis method has been reported.

Preparation of iminodiacetic acid functionalized multi-walled carbon nanotubes and its application as sorbent for separation and preconcentration of heavy metal ions.

In this paper, a novel material was prepared with functionalizing multi-walled carbon nanotubes (MWCNTs) using iminodiacetic acid (IDA) and characterized by FT-IR. Isotherm and kinetics of adsorption were studied and the experimental data fitted the Langmuir model and pseudo-second-order equation very well. An on-line method for simultaneous determination of trace V (V), Cr (VI), Pb (II), Cd (II), Co (II), Cu (II) and As (III) in biological samples was developed using this material as sorbent coupled with inductively coupled plasma mass spectrometry (ICP-MS). A series of experimental parameters, including sample pH, sample flow rate and loading time, eluting solution and the effect of interfering ions have been investigated systematically. Under the optimum experimental conditions, the enrichment factors for above metal ions were ranged from 66 to 101. Detection limit (3 s) was achieved at 1.3, 1.2, 0.70, 0.40, 2.5, 3.4, 0.79 ng L(-1), respectively. At the 1.0 µg L(-1) level, the precision (RSD, %) for 11 replicate measurements was from 1.0 to 4.0. In spiked biological samples, good recoveries (n=3) were obtained in the range of 90-110%. These results had proved that the proposed method was with good accuracy and could be applied to the analysis of trace metal ions in biological samples.

General method for synthesis of 2-heterocyclic N-methyliminodiacetic acid boronates.

A wide range of 2-pyridyl and other difficult-to-access heterocyclic N-methyliminodiacetic acid boronates can be readily prepared from the corresponding bromides via a new method involving direct transligation of 2-heterocyclic trialkoxyborate salts with N-methyliminodiacetic acid (MIDA) at elevated temperatures.

Design of potential reverse transcriptase inhibitor containing Isatin nucleus using molecular modeling studies.

Two Dimensional (2D) and Three Dimensional (3D) Quantitative Structure-Activity Relationship (QSAR) studies were performed for correlating the chemical composition of Isatin analogues and their anti-HIV activity using Multiple Linear Regression (MLR) Analysis and k Nearest Neighbor Molecular Field Analysis (kNN MFA), respectively. New Chemical Entities (NCEs) were designed using results of QSAR studies. Binding affinities of designed NCEs were studied on Reverse Transcriptase enzyme using docking studies and their ADME properties were also predicted. Finally most promising compounds were selected from molecular modeling studies. Five compounds containing Isatin nucleus were synthesized and tested for their anti-HIV activity by performing Reverse Transcriptase Assay. Three compounds showed significant Reverse Transcriptase inhibiting activity compared to standard Navirapine. Structure-Activity Relationships were also discussed bases on obtained molecular modeling and experimental data.

Asymmetric transfer hydrogenation of beta,gamma-alkynyl alpha-imino esters by a Brønsted acid.

Asymmetric synthesis of trans-alkenyl alpha-amino esters was realized by chiral phosphoric acid catalyzed transfer hydrogenation of beta,gamma-alkynyl alpha-imino esters. Utilizing Hantzsch esters as the hydrogen donor, both the alkyne and imine moieties of beta,gamma-alkynyl alpha-imino esters were reduced to afford trans-alkenyl alpha-amino esters with up to 96% ee.