PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Macrocyclic Compounds”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31Linked to original sources
PubMed2006

Viral kinetics in patients with chronic hepatitis C treated with the serine protease inhibitor BILN 2061.

We analysed viral kinetics from a 2-day treatment with BILN 2061, a serine protease inhibitor of hepatitis C virus, in patients chronically infected with genotype 1 hepatitis C virus. The efficiency (E), describing inhibition of viral production, was above 99.45% in all patients with minor or moderate fibrosis receiving doses of 200mg and 500 mg twice daily and larger than in previous studies for interferon-based treatments. However, epsilon was slightly smaller in patients with cirrhosis given 200mg and markedly smaller in patients given 25 mg. Estimates of viral clearance and infected-cell loss support conclusions on these rates and on treatment mechanisms from previous studies on interferon-alpha-based treatments.

Adult↗
PubMedDate not supplied

Assessment of the macrocyclic effect for the complexation of crown-ethers with alkali cations using the Substructural Molecular Fragments method.

The Substructural Molecular Fragments method (Solov'ev, V. P.; Varnek, A. A.; Wipff, G. J. Chem. Inf. Comput. Sci. 2000, 40, 847-858) was applied to assess stability constants (logK) of the complexes of crown-ethers, polyethers, and glymes with Na+, K+, and Cs+ in methanol. One hundred forty-seven computational models including different fragment sets coupled with linear or nonlinear fitting equations were applied for the data sets containing 69 (Na+), 123 (K+), and 31 (Cs+) compounds. To account for the "macrocyclic effect" for crown-ethers, an additional "cyclicity"descriptor was used. "Predicted" stability constants both for macrocyclic compounds and for their open-chain analogues are in good agreement with the experimental data reported earlier and with those studied experimentally in this work. The macrocyclic effect as a function of cation and ligand is quantitatively estimated for all studied crown-ethers.

Journal Article↗
PubMed2002

Structure-activity relationships of methoctramine-related polyamines as muscular nicotinic receptor noncompetitive antagonists. 3. Effect of inserting the tetraamine backbone into a macrocyclic structure.

The present article expands on the study of another aspect of structure-activity relationships of the polymethylene tetraamines, namely, the effect of inserting the tetraamine backbone into a macrocyclic structure. To this end, compounds 8-12 were designed by linking the two terminal nitrogen atoms of prototype methoctramine 2 to an aryl moiety. Alternatively, 2 was first modified to achieve compounds 6 and 7, which in turn were cyclized by linking the two terminal primary amine functions to a polyphenyl spacer, affording 13-20. All the compounds were tested on muscle-type nAChRs and most of them as well on AChE. Furthermore, selected compounds were tested also on peripheral M(2) and M(3) mAChRs. All these cyclic derivatives, like prototypes, were potent noncompetitive antagonists at both frog and Torpedo nAChRs, suggesting that polyamines do not need to be linear or in extended conformation to optimally interact with the nicotinic channel; rather, they may bind in a U-shaped conformation. Relative to muscarinic activity, macrocyclic compounds 10, 13, 14, and 20, in contrast with the profile displayed by 2, were almost devoid of affinity. It is derived that an aryl spacer is detrimental to the interaction of polyamines with mAChRs. Finally, all the diamine diamides investigated in this study were much less potent in inhibiting AChE activity than prototype 3, suggesting that a macrocyclic structure may not be suitable for AChE inhibition.

Acetylcholinesterase↗
PubMed2001

Synthesis of aluminum hydrazides by hydroalumination of 2,3-diazabutadienes--formation of an Al4(N2)3 cage compound and an Al3(N2)3 macrocyclic ligand.

Treatment of 1,1,4,4-tetramethyl-2,3-diazabutadiene with the alane adduct [AlH3(NMe2Et)] yielded the hydrazine derivative (AlH2)2-(AlH)2(N2iPr2)3 (1) by the hydroalumination of both C N double bonds. Compound 1 has a complicated cage structure formed by three hydrazido groups and four aluminium atoms. As a particularly interesting structural motif it contains a N-N group side-on-coordinated to one aluminium atom through its lone pairs of electrons. Sublimation of 1 gave a heterocubane-type compound (HAlNiPr)4 (2) by the complete cleavage of all N-N bonds, one face of which is bridged by weakly coordinated diisopropyldiazene with a N-N double bond. Repeated sublimation gave the pure, unsupported heterocubane molecule 3. Heating of the rough product of the reaction of alane and diazabutadiene to 90 degrees C in a closed vessel yielded another product Al(AlH2)3(N2iPr2)3 (4), which contains a cyclic chelating ligand formed by three hydrazido groups and three aluminium atoms. This heterocycle coordinates a fourth aluminum atom in the molecular center by close contacts to all six nitrogen atoms. A strongly flattened, distorted octahedral coordination sphere results for the inner metal atom.

Journal Article↗
PubMed2005

Metabolites produced by nitrogen-fixing Nostoc species.

This paper provides a comprehensive overview of metabolites, including lipids and lipid-like compounds, boron-containing macrocycles, arsenolipids, oligopeptides and amino acid derivatives, produced by cyanobacteria of the genus Nostoc.

Amino Acids↗
PubMed2002

Intramolecular electronic energy transfer in bichromophoric macrocyclic complexes.

Efficient intramolecular electronic energy transfer (EET) has been demonstrated for three novel bichromophoric compounds utilizing a macrocyclic spacer as the bridge between the electronic energy donor and acceptor fragments. As their free base forms, emission from the electronically excited donor is absent and the acceptor emission is reductively quenched via photoinduced oxidation of proximate amine lone pairs. As their Zn(II) complexes, excitation of the donor results in sensitization of the electronic acceptor emission.

Journal Article↗
PubMed1984

Antileukemic compounds derived by chemical modification of macrocyclic trichothecenes. 2. Derivatives of roridins A and H and verrucarins A and J.

Various 8 beta-hydroxy, 16-hydroxy, and 9 beta,10 beta-epoxy derivatives of roridins A and H and verrucarins A and J have been prepared and tested in vivo against P388 mouse leukemia. The 9 beta,10 beta-epoxy derivatives and 16-hydroxy derivatives consistently exhibit very high activity. The 8 beta-hydroxy-9 beta,10 beta-epoxy and 16-hydroxy-9 beta,10 beta-epoxy derivatives of verrucarin A and roridin A exhibit extraordinary activity against P388. The 8 beta-hydroxy-9 beta,10 beta-epoxy and 16-hydroxy-9 beta,10 beta-epoxy derivatives of verrucarin A and roridin A exhibit extraordinary against P388.

Animals↗
PubMed2004

A macrocyclic nitrosyl ruthenium complex is a NO donor that induces rat aorta relaxation.

The vasorelaxation induced by a nitrosyl macrocyclic ruthenium complex, proposed as a new nitric oxide (NO) carrier, was studied in rat isolated aorta. The compound trans-[RuCl([15]aneN4)NO]2+ was characterized by elemental analysis, UV-visible spectrum, and infrared spectrum. Based on the electrochemical process, the reduction of the compound was followed by NO release, which was also observed using norepinephrine as a reducing agent and NO released was analyzed by a sensor. Vasorelaxation induced by this NO donor was studied and compared to those obtained with sodium nitroprusside (SNP). The relaxation induced by the compound was concentration-dependent in denuded rat aortas and occurred only in pre-contracted arteries with norepinephrine. The macrocyclic compound induced relaxation with a similar efficacy as SNP, although the potency of SNP was slightly greater. The time to reach maximum relaxation (595 s) was longer than that of SNP (195 s). Relaxation was completely abolished by oxyhemoglobin, a known NO scavenger.

Animals↗
PubMed2000

A donor-acceptor compound composed of a dinuclear zinc(II) complex of a robson macrocycle with 8-methylquinoline

A donor-acceptor compound, diaqua-1kappaO,2kappaO-[&mgr;-11, 23-dimethyl-3,7,15,19-tetraazatricyclo[19.3.1.1(9,13)]hexacosa-1(25), 2,7,9,11,13(26),14,19,21,23-decaene-25,26-diolato-1kappa(4)N(3),N(7), O(25),O(26):2kappa(4)N(15),N(19),O(25),O(26)]dizinc(II) diperchlorate bis(8-methylquinoline) ethanol disolvate, [Zn(2)(C(24)H(26)N(4)O(2))(H(2)O)(2)](ClO(4))(2).2C(10)H(9)N. 2C(2)H(6)O, obtained by the reaction of a dinuclear zinc(II) complex of a Robson macrocycle (acceptor) and 8-methylquinoline (donor), lies about an inversion centre and the coordination about the unique Zn atom is a distorted square pyramid. The fifth coordination site is occupied by the water molecule, Zn-O = 2.016 (2) A, and the average macrocyclic Zn-O and Zn-N distances are 2.059 (6) and 2.059 (3) A, respectively.

Journal Article↗
PubMed2004

Highly nonplanar, electron deficient, N-substituted tetra-oxocyclohexadienylidene porphyrinogens: structural, computational, and electrochemical investigations.

The structures and electrochemistry of N-benzylated meso-tetrakis (3,5-di-tert-butyl-4-oxo-cyclohexa-2,5-dienylidene) porphyrinogens have been investigated. Structural determinations reveal the isomeric identity of the products obtained from the N-alkylation of the parent meso-tetra (oxo-cyclohexadienylidene) porphyrinogen. The compounds are subject to increased macrocyclic deformations upon increasing N-substitution culminating in the tetra-N-benzyl derivative, which has a buckling superimposed on the already highly puckered macrocycle. The electrochemical analyses emphasize the electron deficiency of the N-benzylated meso-tetra(oxo-cyclohexadienylidene) porphyrinogens and indicate that they can be considered as quinones conjugated via the unsaturated tetrapyrrolic macrocycle. The N-benzylated compounds studied form stable and well-defined pi-cation radical and pi-anion radical species because of their highly conjugated nature. Ab initio molecular orbital calculations at the B3LYP/3-21G() level confirmed the high degree of conjugation between tetrapyrrole and meso substituents and also gave good agreement between calculated and experimentally determined HOMO-LUMO band gap energies.

Journal Article↗
PubMed2005

Reaction pathways leading to arylene ethynylene macrocycles via alkyne metathesis.

Mechanistic studies on the direct formation of arylene ethynylene macrocycles via alkyne metathesis catalyzed by a molybdenum complex are reported. Gel permeation chromatography (GPC) and matrix-assisted laser desorption ionization (MALDI) mass spectrometry on the products from metathesis of monomer 1 show the initial formation of linear oligomers and large macrocycles (n > 6), followed by their transformation into the thermodynamically most stable product distribution-mainly the cyclic hexamer. Variable temperature and scrambling experiments reveal the reversibility of macrocycle formation. Nearly identical product distributions are observed from the cross metathesis of hexacycle 2 with diphenylacetylene and from the metathesis of bis(phenylethynyl) substituted monomer 4, demonstrating that macrocycle formation is thermodynamically rather than kinetically controlled. The metathesis byproduct, 3-hexyne, is shown to inhibit the catalyst. It is suggested that the relative metathesis rates of dialkylalkynes versus diarylalkynes trap the catalyst in a nonproductive manifold, rendering it unavailable for the productive metathesis of aryl alkylalkyne substrates. This finding indicates that dialkyl-substituted alkyne byproducts should be avoided (or efficiently removed) if the metatheses of aryl substrates, especially those with electron-withdrawing groups, are to proceed to high conversion.

Alkynes↗
PubMed2001

(6,17-Dimethyl-8,15-diphenyldibenzo[b,i][1,4,8,11]-tetra-aza[14]annulenato)nickel(II) in solids: two guest-free polymorphs and inclusion compounds with methylene chloride and fullerene (C(60))-carbon disulfide.

Two guest-free polymorphs and two inclusion compounds of the macrocyclic title complex [NiL] have been isolated and characterized with single-crystal and/or powder XRD, solid-state (13)C NMR, and other methods. The inclusion compound with methylene chloride, [NiL](CH(2)Cl(2)), is stable in air and thermally stable up to approximately 128 degrees C. Its crystal structure is consistent with van der Waals packing of the host [NiL] and guest CH(2)Cl(2) molecules. The host complex has square-planar coordination of the nickel(II) center with four nitrogen atoms of the macrocycle with an average Ni-N distance of 1.86 A. The molecule has a saddle-shaped conformation with the guest molecule located between one phenylene and two phenyl rings of the host molecule. Isostructural compounds with chloroform and 2-chloropropane form only as mixtures along with a guest-free host polymorph. The inclusion compound with C(60) has a composition 3[NiL]*(C(60))*2(CS(2)) and here also the crystal structure is consistent with a van der Waals type of packing. Three crystallographically inequivalent [NiL] molecules have geometries similar to that in the inclusion compound with methylene chloride. The concave surfaces of the complex molecules form a spherical cavity for the C(60) molecule. At -100 degrees C the C(60) molecule is disordered over two orientations centered at the same site. (13)C NMR studies at room temperature show that the C(60) molecule is undergoing rapid pseudo-isotropic rotation. The stability and other properties of the title and related complexes are discussed.

Journal Article↗
PubMed2006

Chemical and spectroscopic evidence for an FeV-oxo complex.

Iron(V)-oxo species have been proposed as key reactive intermediates in the catalysis of oxygen-activating enzymes and synthetic catalysts. Here, we report the synthesis of [Fe(TAML)(O)]- in nearly quantitative yield, where TAML is a macrocyclic tetraamide ligand. Mass spectrometry, Mössbauer, electron paramagnetic resonance, and x-ray absorption spectroscopies, as well as reactivity studies and density functional theory calculations show that this long-lived (hours at -60 degrees C) intermediate is a spin S = 1/2 iron(V)-oxo complex. Iron-TAML systems have proven to be efficient catalysts in the decomposition of numerous pollutants by hydrogen peroxide, and the species we characterized is a likely reactive intermediate in these reactions.

Catalysis↗
PubMed1980

Antileukemic compounds derived from the chemical modification of macrocyclic trichothecenes. 1. Derivatives of verrucarin A.

Verrucarin A (2) was epoxidized to give the beta-9,10-epoxide 7 (major product) and alpha-9,10-epoxide 9 (minor product). The beta-epoxide 7 and its acetate 8 exhibit high in vivo antileukemic activity against P-388 mouse leukemia, whereas 2 and 9 are inactive. Epoxidation of verrucarin B (3) and roridin A (1) to their respective beta-9,10-epoxides (11 and 12, respectively) also yields compounds with substantially increased activity. Allylic alcohols derived from 2, alpha-C8 (20), beta-C8 (14), and C16 (15), were synthesized and tested; only 15 exhibited substantial in vivo activity.

Animals↗
PubMed2004

Synthesis, characterization, and X-ray crystal structures of cyclam derivatives. 5. Copper(II) binding studies of a pyridine-strapped 5,12-dioxocyclam-based macrobicycle.

The copper(II) binding properties of the macrobicyclic diamide 1,9,12,18,22-pentaazatricyclo[7.6.6.1(3,7)]docosa-3,5,7(22)-triene-13,19-dione (L1) have been fully investigated by spectroscopic (IR, UV-vis, EPR, MALDI-TOF MS), X-ray diffraction, potentiometric, electrochemical, and spectroelectrochemical methods. This constrained receptor possesses a hemispherical cavity created by cross-bridging the 1 and 8 positions of trans-dioxocyclam (1,4,8,11-tetraazacyclotetradecane-5,12-dione, L2) with a 2,6-pyridyl strap. Treatment of L1 with a copper salt in methanol produces a red complex of [Cu(L1H(-1))]+ formula in which the copper atom is embedded in a 13-membered ring and coordinated by both amines as well as the pyridine and one deprotonated amide nitrogen atoms. Infrared spectroscopy provides evidence for protonation of the carbonyl oxygen atom belonging to the copper-bound amide of [Cu(L1H(-1))]+ under strongly acidic conditions. The resulting conversion of the amidate into an iminol group highlights the inert character of the corresponding complexes, which do not dissociate at low pH values. In contrast, both secondary amides of L1 deprotonate in the presence of a weak base, thus affording a blue pentacoordinated [Cu(L1H(-2))] compound where the copper atom sits in the center of the 14-membered dioxocyclam fragment. In aqueous solution, both complexes undergo a pH-driven (pK(a) = 8.73(2)) molecular reorganization, which is reminiscent of a glider motion. The copper(II) cation switches rapidly and reversibly from a four-coordinate flattened tetrahedral arrangement of the donor atoms in the red species to a five-coordinate environment in the blue species, which is intermediate between a square pyramid and a trigonal bipyramid. Conversion of the red to the blue form was also demonstrated to occur upon reduction of [Cu(L1H(-1))]+ by cyclic voltammetry (E(pc) = -0.64 V/SCE in CH(3)CN).

Copper↗
PubMed2004

Temperature and enantioseparation by macrocyclic glycopeptide chiral stationary phases.

Seventy-one chiral compounds were separated on four macrocyclic glycopeptide chiral selectors: teicoplanin, its aglycone, ristocetin A and vancomycin, using three possible separation modes: reversed phase with methanol/buffer mobile phases, normal phase with hexane/ethanol mobile phases and polar ionic mode (PIM) with 100% methanol mobile phase with trace amounts of acid and/or base. These 148 separations were studied in a 5-45 degrees C temperature range. Peak efficiencies always increased with temperature, but in only 17% of the separations studied a small increase of the enantioresolution factor was observed. In the majority (83%) of the cases, the enantioresolution decreased or even vanished when temperature increased. All 148 Van't Hoff plots were linear showing that the selector did not change in the temperature range studied. The calculated enthalpy and entropy variations showed that the interaction of the solute with the stationary phase was always enthalpy driven with normal and reversed mobile phases. It could be enthalpy as well as entropy driven with PIM mobile phases strongly dependent on the solute. The plots of delta(deltaH) versus delta(deltaS) were linear in most cases (enthalpy entropy compensation). This observation cannot be used to give clear information on chiral recognition mechanisms, but it allowed identifying specific stationary phase-solute interactions because the points corresponding to the respective thermodynamic parameters were clearly delineated from the general compensation lines.

Glycopeptides↗
PubMed1998

Combinatorial chemistry in insects: a library of defensive macrocyclic polyamines.

The pupal defensive secretion of the coccinellid beetle Epilachna borealis is composed principally of a combinatorial library of macrocyclic polyamines. These compounds constitute a previously unrecognized family of natural products, characterized by extremely large-ring lactonic structures derived from a small set of (2-hydroxyethylamino)alkanoic acids. The combinatorial assembly of these simple building blocks generates a high degree of structural diversity, which is further increased by slow, spontaneous intramolecular rearrangement of the macrocycles.

Amino Acids↗