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PubMed2003

Macrocyclic amines as catalysts of the hydrolysis of the triphosphate bridge of the mRNA 5'-cap structure.

The reactions of a 5'-cap model compound P1-(7-methylguanosine) P3-guanosine 5',5'-triphosphate, m7GpppG, were studied in the presence of three different macrocyclic amines (2-4) under neutral conditions. The only products observed in the absence of the macrocycles resulted from the base-catalysed imidazole ring-opening and the acid-catalysed cleavage of the N7-methylguanosine base, whereas in the presence of these catalysts hydrolysis of the triphosphate bridge predominated. The latter reaction yielded guanosine 5'-monophosphate, guanosine 5'-diphosphate, 7-methylguanosine 5'-monophosphate and 7-methylguanosine 5'-diphosphate as the initial products, indicating that both of the phosphoric anhydride bonds were cleaved. The overall catalytic activity of all three macrocycles was comparable. The hydrolysis to guanosine 5'-diphosphate and 7-methylguanosine 5'-monophosphate was slightly more favoured than the cleavage to yield guanosine 5'-monophosphate and 7-methylguanosine diphosphate. All the macrocycles also enhanced the subsequent hydrolysis of the nucleoside diphosphates, 2 being more efficient than 3 and 4.

Amines↗
PubMed2003

Complexation of silver and co-recovered metals with novel aza-crown ether macrocycles by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) is used to evaluate the metal binding selectivities of an array of novel caged macrocycles for silver, gold, copper, nickel, zinc, iron, lead, manganese and alkali metal ions. It is found that five of the new compounds display silver selectivity, and their relative affinities for various metals depend on the type, number, and arrangement of heteroatoms (N, O), the cavity size, and the presence of aromatic substituents. Alkali metal cation binding studies are used to evaluate the size-selectivities of the cavities of the macrocycles. Electronic structure calculation by B3LYP density function theory methods were used to model the metal complexes. The presence of nitrogen atoms in the macrocyclic ring is essential for silver selectivity over other transition metals and alkali metal ions, and the presence of aromatic groups also enhances silver avidity. Macrocycle 3, a triaza-18-crown-6 analog modified with two phenyl groups and a cage group, is capable of selective extraction of Ag+ from aqueous solutions in the presence of other transition metal ions and the most common alkali and alkaline earth metal ions.

Crown Ethers↗
PubMed2005

Cadmium(II) and mercury(II) complexes of an NO2S2-donor macrocycle and its ditopic xylyl-bridged analogue.

The NO2S2-donor macrocycle (L1) was synthesised from the ring closure reaction between Boc-N-protected 2,2'-iminobis(ethanethiol) (3) and 2,2'-(ethylenedioxy)bis(benzyl chloride) (4) followed by deprotection of the Boc-group. alpha,alpha'-Dibromo-p-xylene was employed as a dialkylating agent to bridge two L1 to yield the corresponding N-linked product (L2). The X-ray structure of L2 (as its HBr salt) is described. A range of Cd(II) and Hg(II) complexes of L1 (6-9) and L2 (10-12) were prepared and characterised. Reaction of HgX2 (X = Br or I) with L1 afforded [Hg(L1)Br]2[Hg2Br6].2CH2Cl2 6 and [Hg(L1)I(2)] 7, respectively. For 6, the Hg(II) ion in the complex cation has a distorted tetrahedral coordination environment composed of S2N donor atoms from L1 and a bromo ligand. In 7 the coordination geometry is highly distorted tetrahedral, with the macrocycle coordinating in an exodentate manner via one S and one N atom. The remaining two coordination sites are occupied by iodide ions. [Hg(L1)(ClO4)]ClO4 8 was isolated from the reaction of Hg(ClO4)2 and L1. The X-ray structure reveals that all macrocyclic ring donors bind to the central mercury ion in this case, with the latter exhibiting a highly distorted octahedral coordination geometry. The O2S2-donors from the macrocyclic ring define the equatorial plane while the axial positions are occupied by the ring nitrogen as well as by an oxygen from a monodentate perchlorato ion. Reaction of Cd(NO3)(2).4H2O with L1 afforded [Cd(L1)(NO3)2](.)0.5CH2Cl2 9 in which L1 acts as a tridentate ligand, binding exo-fashion via its S2N donors. The remaining coordination positions are filled by two bidentate nitrate ions such that, overall, the cadmium is seven-coordinate. Reactions of HgX2(X = Br or I) with L2 yielded the isostructural 2 : 1 (metal : ligand) complexes, [Hg2(L2)Br4] 10 and [Hg2(L2)I(4)] 11. Each mercury ion has a distorted tetrahedral environment made up of S and N donors from an exodentate L2 and two coordinated halides. Contrasting with this, the reaction of L2 with Cd(NO3)(2).4H2O yielded a 1-D coordination network, {[Cd2(L2)(NO3)4].2CH2Cl2}n 12 in which each ring of L2 is exo-coordinated via two S atoms and one N atom to a cadmium ion which is also bound to one monodentate and one bidentate nitrate anion. The latter also has one of its oxygen atom attached to a neighboring cadmium via a nitroso (mu2-O) bridge such that the overall coordination geometry about each cadmium is seven-coordinate. The [Cd(L2)0.5(NO3)2] units are linked by an inversion to yield the polymeric arrangement.

Journal Article↗
PubMed2006

Shape-persistent macrocyclic aromatic tetrasulfonamides: Molecules with nanosized cavities and their nanotubular assemblies in solid state.

Alkoxy side-chain-flanked diarylsulfonamide serves as a reliable structural motif for constructing macrocyclic aromatic tetrasulfonamides. This 90 degrees structural motif is persistent both in solution and in the solid state, which allows the one-step formation of tetrasulfonamide macrocycles. These macrocycles adopt a cone-shaped conformation in solution and in the solid state. For each molecule, an interior cavity surrounded by the aromatic residues is formed. The cavity sizes of the macrocycles can be tuned by incorporating aromatic residues of proper sizes. Guest (solvent) molecules are found in the cavities and bound by side chains. In solution, 1H NMR shows that the cone conformations undergo rapid interconversion at room temperature. The alkoxy side chains are found to be indispensable for maintaining the cone conformation. In addition, these porous molecules self-assemble into hollow tubular structures in the solid state. A variety of host molecules and building blocks for constructing nanoporous solid-state structures can be expected from these molecules.

Journal Article↗
PubMed2003

Modulation of lipopolysaccharide-induced proinflammatory cytokine production by satratoxins and other macrocyclic trichothecenes in the murine macrophage.

The satratoxins and other macrocyclic trichothecene mycotoxins are produced by Stachybotrys, a mold that is often found in water-damaged dwellings and office buildings. To test the potential immunomodulatory effects of these mycotoxins, RAW 264.7 murine macrophage cells were treated with various concentrations of satratoxin G (SG), isosatratoxin F (iSF), satratoxin H (SH), roridin A (RA), and verrucarin A (VA) for 48 h in the presence or absence of suboptimal concentra-tion of lipopolysaccharide (LPS, 50 ng/ml), and tumor necrosis factor-alpha (TNF-alpha ) and interleukin-6 (IL-6) production were assayed by enzyme-linked immunosorbent assay (ELISA). In LPS-stimulated cultures, TNF-alpha supernatant concentrations were significantly increased in the presence of 2.5, 2.5, and 1 ng/ml of SG, SH, and RA, respectively, whereas IL-6 concentrations were not affected by the same concentrations these macrocyclic trichothecenes. When cells that were treated with LPS and SG (2.5 ng/ml) were evaluated by real-time polymerase chain reaction (PCR),TNF-alpha mRNA was found to increase at 24, 36, and 48 h compared to control cells. At higher concentrations, cytokine production and cell viability were markedly impaired in LPS-stimulated cells. Without LPS stimulation, neither TNF-alpha, nor IL-6 was induced. These results indicate that low concentrations of macrocyclic trichothecenes superinduce expression of TNF-alpha, whereas higher concentrations of these toxins are cytotoxic and concurrently reduce cytokine production. The capacity of satratoxins and other macrocyclic trichothecenes to alter cytokine production may play an etiologic role in outbreaks of Stachybotrys-associated human illnesses.

Analysis of Variance↗
PubMed2004

Amphids: the neuronal ultrastructure of macrocyclic-lactone-resistant Haemonchus contortus.

The development of anthelmintic resistance by nematode parasites is a growing problem for veterinarians and producers. The intensive use of the macrocyclic lactones for the treatment of a variety of parasitic diseases has hastened the development of resistance to this family of parasiticides among sheep, goats and cattle. As a result, resistance to ivermectin, moxidectin and doramectin by Haemonchus contortus has been documented throughout the world. While the exact sites of action of the macrocyclic lactones remain incompletely known, a critical point of entry for these drugs may be the terminally exposed sensory major neurons located in the cephalic end of the worms. These neurons, called amphidial neurons, are located in a pair of channels, the amphids, on either side of the pharynx and are exposed to the external environment via pores at the anterior tip of the worm. Through these neurons, important chemical and thermal cues are gathered by the parasite. Examination of serial electron micrographs of ivermectin-susceptible and ivermectin-resistant H. contortus allows for comparison of neuronal structure, arrangement of neurons within the amphidial channel, and distance of the tip of the dendritic processes to the amphidial pore. The latter of these characteristics provides a useful means by which to compare the association between the neurons and the external environment of the worm. Comparison of parental laboratory strains of ivermectin-susceptible H. contortus with related selected, ivermectin-resistant strains and with a wild-type ivermectin-susceptible field strain of H. contortus from Louisiana reveals that the ivermectin-resistant worms examined have markedly shorter sensory cilia than their ivermectin-susceptible parental counterparts. Additionally, the amphidial neurons of ivermectin-resistant worms are characterized by generalized degeneration and loss of detail, whereas other neurons outside of the channels, such as the labial and cephalic neurons, are normal in structure. Similar degeneration was also observed in field strains of doramectin-resistant H. contortus collected from a New Jersey alpaca heard. These findings raise a number of questions regarding the relationship between amphidial structure and macrocyclic lactone resistance as well as the role of amphids as a means of entry for these molecules. While shortened amphidial sensilla are associated with ivermectin resistance, it remains unclear if such a structural modification facilitates survival of nematodes exposed to the macrocyclic lactones.

Animal Structures↗
PubMed2004

New macrocyclic musk compounds.

The syntheses and olfactory evaluations of eight new macrocyclic musks with a 1,6-dioxa structure (1a-d and 1'a-d) as well as of twelve optically active 3-methyl macrolides (5a-c and 5'a-c) are reported. These macrocycles were synthesized via intramolecular metathesis mediated by the Grubbs catalyst. Despite the absence of a C=O function, the 1,6-dioxa compounds, both unsaturated (1) and saturated (1'), possess musky odors similar to those of macrocyclic ketones and lactones. Especially 16-membered rings were found to display an intense and pleasant musk character. However, in the case of optically active 3-methyl macrolides (5, 5'), only the (R)-configured 15- and 16-membered rings had intense and pleasant musk notes.

Fatty Acids, Monounsaturated↗
PubMed2006

Theoretical investigations on the geometric and electronic structures of phenylene-acetylene macrocycles.

The geometric and electronic structures of a series of conjugated macrocycles (phenylene-acetylene macrocycles, PAMs) have been studied theoretically with ab initio and semiempirical molecular orbital methods. The ab initio calculations at the HF/6-31G* level demonstrate that the model molecules may have a planar conformation. Bigger macrocycles, for example, 7PAM, 8PAM, and 9PAM, result in several energy minima. The boatlike conformation is the most energetically favored form. Based on the conformational analysis, a novel method for analyzing the ring-strain energy was proposed and used. In view of their potential applications as electronic materials, the electronic structures of a series of PAMs are also investigated. The LUMO-HOMO gaps of the planar PAMs show an odd-even difference behavior. In addition, the HOMOs of the planar species 3PAM, 5PAM, 7PAM, and 9PAM are doubly degenerated.

Acetylene↗
PubMed2006

HPLC separation of amino acid enantiomers and small peptides on macrocyclic antibiotic-based chiral stationary phases: a review.

The search for new and effective chiral selectors capable of separating a wide variety of enantiomeric compounds is an ongoing process. In the past decade, macrocyclic antibiotics have proved to be an exceptionally useful class of chiral selectors for the separation of enantiomers of biological and pharmacological importance by means of HPLC, TLC and electrophoresis. More chiral analytes have been resolved through the use of glycopeptides than with all the other macrocyclic antibiotics combined (ansamycins, thiostrepton, aminoglycosides, etc.). The glycopeptides avoparcin, teicoplanin, ristocetin A and vancomycin have been extensively used as chiral selectors in the form of chiral bonded phases in HPLC, and HPLC stationary phases based on these glycopeptides have been commercialized. Teicoplanin, vancomycin, their analogs and ristocetin A seem to be the most useful glycopeptide HPLC bonded phases for the enantioseparation of proteins and unusal native and derivatized amino acids. In fact, the macrocyclic glycopeptides are to some extent complementary to one another: where partial enantioresolution is obtained with one glycopeptide, there is a high probability that baseline or better separation can be obtained with another. This review sets out to characterize the physicochemical properties of these antibiotics and their application in the enantioseparations of amino acids. The mechanism of separation, the sequence of elution of the stereoisomers and the relation to the absolute configuration are also discussed.

Amino Acids↗
PubMed2005

Evaluation of macrocyclic Grb2 SH2 domain-binding peptide mimetics prepared by ring-closing metathesis of C-terminal allylglycines with an N-terminal beta-vinyl-substituted phosphotyrosyl mimetic.

Preferential binding of ligands to Grb2 SH2 domains in beta-bend conformations has made peptide cyclization a logical means of effecting affinity enhancement. This is based on the concept that constraint of open-chain sequences to bend geometries may reduce entropy penalties of binding. The current study extends this approach by undertaking ring-closing metathesis (RCM) macrocyclization between i and i+3 residues through a process involving allylglycines and beta-vinyl-functionalized residues. Ring closure in this fashion results in minimal macrocyclic tetrapeptide mimetics. The predominant effects of such macrocyclization on Grb2 SH2 domain binding affinity were increases in rates of association (from 7- to 16-fold) relative to an open-chain congener, while decreases in dissociation rates were less pronounced (approximately 2-fold). The significant increases in association rates were consistent with pre-ordering of solution conformations to near those required for binding. Data from NMR experiments and molecular modeling simulations were used to interpret the binding results. An understanding of the conformational consequences of such i to i+3 ring closure may facilitate its application to other systems where bend geometries are desired.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Macrocyclic inhibitors of the malarial aspartic proteases plasmepsin I, II, and IV.

The first macrocyclic inhibitor of the Plasmodium falciparum aspartic proteases plasmepsin I, II, and IV with considerable selectivity over the human aspartic protease cathepsin D has been identified. A series of macrocyclic compounds were designed and synthesized. Cyclizations were accomplished using ring-closing metathesis with the second generation Grubbs catalyst. These compounds contain either a 13-membered or a 16-membered macrocycle and incorporate a 1,2-dihydroxyethylene as transition state mimicking unit. The binding mode of this new class of compounds was predicted with automated docking and molecular dynamics simulations, with an estimation of the binding affinities through the linear interaction energy (LIE) method.

Animals↗
PubMed2004

Enhanced macrocyclizing activity of the thioesterase from tyrocidine synthetase in presence of nonionic detergent.

Macrocyclization carried out by thioesterase domains of multimodular nonribosomal peptide synthetases (NRPSs) is a key step in the biosynthesis of many biologically active peptides. The thioesterase excised from tyrocidine synthetase is a versatile macrocyclization catalyst and a useful tool for chemoenzymatic synthesis of diverse cyclic peptides. However, its utility is limited by its short lifetime of catalytic activity as well as significant flux of the acyl-enzyme intermediate to hydrolysis. The addition of Brij 58, a nonionic detergent, above the critical micelle concentration, has dramatic effects on enzyme activity: catalytic activity is extended to >60 min and the rate of cyclization (but not hydrolysis) increases 6-fold, resulting in a net 150- to 300-fold increase in cyclic product yields. This enhanced activity allowed enzymatic macrocyclization of a solid phase library of tyrocidine decapeptides to identify acceptable substitutions at the Orn9 position which had previously been inaccessible for diversification.

Amino Acid Substitution↗
PubMed2006

Spectral studies with coordination behaviour of (NO3) and (NCS) anions and EPR parameters of chromium(III) complexes which have different chromospheres macrocyclic ligands: synthesis and electronic spectroscopy.

New macrocyclic ligands were prepared and chromium(III) stability in the marcrocyclic cavities are reported. Two of them have four-coordinate [N2O2]:[N4], third one has five-coordinate [N2O2S] and the last one has six-coordinate [N4O2] donor macrocyclic cavities. These macrocyclic ligands have been synthesized with their chromium(III) complexes which have mononuclear nature and their structural features have been discussed on the basis of: elemental analysis, magnetic moment, electronic, IR, 1H NMR, and EPR spectral studies. All the chromium(III) complexes show magnetic moments in the range of 3.74-3.80 B.M. corresponding to high-spin configuration. However, the interaction of oxygen to the chromium ion in complexes is much weaker than that of other donor atoms. The spin-orbit coupling parameter, z, gives no significance because the splitting of doublet transition lines are too large to be explained by spin-orbit coupling. The beta values (0.75-0.79) indicate the covalent character, which is due to the presence of sigma bond between the metal/ligand. lambda values indicate that the complexes under study have substantial covalent character and their g-values have also been calculated by using spin-orbital coupling constant (lambda).

Anions↗
PubMed2006

Spectroscopic techniques and cyclic voltammetry with synthesis: manganese(II) coordination stability and its ligand field parameters effect on macrocyclic ligands.

Manganese(II) macrocyclic complexes are prepared with different macrocyclic ligands, containing cyclic skeleton bearing organic components which have different chromospheres like N, O and S donor atoms and stereochemistry. Thus, six macrocyclic ligands, were prepared and their capacity to retain the manganese(II) ion in solid as well as in aqueous solution was determined and characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, mass, (1)H NMR, IR, electronic spectral and cyclic voltammetric studies. The electronic spectrum of this system showed a dependence that may be consistent with the formation of stable complexes and coordination behaviour of the ions. ESR spectra of all the complexes are recorded in solid as well as solution, which show the oxidation state of the manganese(II). Spin Hamiltonian manganese(II), which can be defined as the magnetic field vector (H): H = gBeta(e)HS + D[S(2)(z) - 35/12] + E[S(2)(z) - S(2)(y)] + ASI + (1/6)a [S(4)(x) + S(4)(y) + S(4)(z) - 707/16] + (1/180)F[(35S(2)(z) - 475)/(2S(2)(z) + 3255/10)] Significant distortion of the manganese(II) ion in observed geometry is evident from the angle subtended by the different membered chelate rings and the angles spanned by trans donor atoms octahedral geometry. Cyclic voltammetric studies indicate that complexes with all ligands undergoes one electron oxidation from manganese(II) to manganese(III) followed by a further oxidation to manganese(IV) at a significantly more positive potential.

Anions↗
PubMed2026

Selective Macrocyclic WEE1 Kinase Inhibitors with Strong Efficacy against Patient-Derived Colorectal Cancer Organoids.

Macrocyclization can enhance the selectivity of acyclic compounds toward structurally similar biological targets such as kinases. WEE1 regulates cellular homeostasis and is a promising target in oncology. The clinical candidate AZD1775 (1) failed to progress past Phase II trials because of patient tolerability issues, likely due to off-target inhibition of polo-like kinase 1 (PLK1). Herein, a computer-aided drug design approach was conducted to develop a macrocycle based on the 1-WEE1 X-ray cocrystal structure. Significantly enhanced WEE1 inhibitory selectivity over PLK1 was determined for leading macrocycle 2, which also demonstrated broader kinome-wide selectivity. Patient-derived organoids from colorectal cancer (CRC) peritoneal and liver metastases, treated with 2, demonstrated comparably strong or enhanced anticancer efficacy compared to that of 1. Against patient-matched normal colon vs primary CRC organoids, 2 potently and selectively treated CRC, as well as enhanced DNA damage compared to 1. Finally, the X-ray cocrystal structure of 2 bound to WEE1 validated its computationally predicted bioactive binding mode.

Humans↗
PubMed2004

Zn(II) coordination to polyamine macrocycles containing dipyridine units. New insights into the activity of dinuclear Zn(II) complexes in phosphate ester hydrolysis.

Zn(II) binding by the dipyridine-containing macrocycles L1-L3 has been analyzed by means of potentiometric measurements in aqueous solutions. These ligands contain one (L1, L2) or two (L3) 2,2'-dipyridine units as an integral part of a polyamine macrocyclic framework having different dimensions and numbers of nitrogen donors. Depending on the number of donors, L1-L3 can form stable mono- and/or dinuclear Zn(II) complexes in a wide pH range. Facile deprotonation of Zn(II)-coordinated water molecules gives mono- and dihydroxo-complexes from neutral to alkaline pH values. The ability of these complexes as nucleophilic agents in hydrolytic processes has been tested by using bis(p-nitrophenyl) phosphate (BNPP) as a substrate. In the dinuclear complexes the two metals play a cooperative role in BNPP cleavage. In the case of the L2 dinuclear complex [Zn(2)L2(OH)(2)](2+), the two metals act cooperatively through a hydrolytic process involving a bridging interaction of the substrate with the two Zn(II) ions and a simultaneous nucleophilic attack of a Zn-OH function at phosphorus; in the case of the dizinc complex with the largest macrocycle L3, only the monohydroxo complex [Zn(2)L3(OH)](3+) promotes BNPP hydrolysis. BNPP interacts with a single metal, while the hydroxide anion may operate a nucleophilic attack. Both complexes display high rate enhancements in BNPP cleavage with respect to previously reported dizinc complexes, due to hydrophobic and pi-stacking interactions between the nitrophenyl groups of BNPP and the dipyridine units of the complexes.

2,2'-Dipyridyl↗
PubMed2006

Tubular organization with coiled ribbon from amphiphilic rigid-flexible macrocycle.

We have synthesized an amphiphilic rigid-flexible macrocycle (fcoil = 0.68) consisting of hexa-p-phenylene and aliphatic polyether chain. The macrocyclic molecule in bulk state self-organizes into a 2-D body-centered rectangular structure (a = 4.3 nm and b = 6.3 nm). In aqueous solution, the macrocycle self-assembles into well-defined ribbonlike aggregates with a rod tilt relative to the ribbon normal at the initial stage. These elementary fibrils are further coiled to form a tubular structure consisting of coiled ribbons with a uniform diameter of about 20 nm and a regular pitch of 4.7 nm, as confirmed by TEM experiments. The internal diameter and the wall thickness of the nanotube are measured to be 14 and 3 nm, respectively.

Biomimetic Materials↗
PubMed2006

Giant macrocycles composed of thiophene, acetylene, and ethylene building blocks.

Fully conjugated giant macrocyclic oligothiophenes with 60pi, 90pi,120pi, 150pi, and 180pi frames (1, 2, 3, 4 and 5) have been designed, and their butyl-substituted derivatives (1a, 2a, 3a, 4a, and 5a) have been synthesized using modified Sonogashira and McMurry coupling reactions as key steps. The 60-180pi systems 1-5 are circular with 1.8-6 nm inner cavities and 3.3-7.5 nm outside molecular diameters. Compound 1a containing ten 3,4-dibutyl-2,5-thienylene, eight ethynylene, and two vinylene units has been converted into macrocyclic oligo(3,4-dibutyl-2,5-thienylene-ethynylene) 6a using bromination/dehydrobromination procedure. Giant macrocycles 1a-6a exhibit a red shift of their absorption spectra and a fairly strong fluorescence with a large Stokes shift as compared to a linear conjugated counterpart having five thiophene rings. Compounds 1a-6a exhibit multistep reversible redox behaviors with fairly low first oxidation potentials, reflecting their cyclic conjugation. Furthermore, chemical oxidation of 1a-6a with FeCl3 shows drastic changes of spectroscopic properties due to intramolecular and intermolecular pi-pi interactions. Doping of 1a-3a with iodine forms semiconductor due to its pi-donor properties and pi-pi stacking ability. X-ray analysis of 1a confirmed a round, planar structure with nanoscale inner cavity, and revealed host ability for alkanes and unique packing structure. Interestingly, 2a and 3a self-aggregate in the solid state to form "molecular wires," which are about 200 nm thick and more than 1 mm long. The internal structures of fibrous aggregates have been investigated by optical microscope, scanning electron microscopy, atomic force microscopy, and X-ray diffraction analyses.

Acetylene↗