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PubMed2005

Design, synthesis, linear, and nonlinear optical properties of conjugated (porphinato)zinc(II)-based donor-acceptor chromophores featuring nitrothiophenyl and nitrooligothiophenyl electron-accepting moieties.

An extensive series of conjugated (porphinato)zinc(II)-based chromophores featuring nitrothiophenyl and nitrooligothiophenyl electron-accepting moieties has been synthesized using metal-catalyzed cross-coupling reactions involving [5-bromo-15-triisopropylsilylethynyl-10,20-diarylporphinato]zinc(II) and an unusual electron-rich Suzuki-porphyrin synthon, [5-(4-dimethylaminophenylethynyl)-15-(4',4',5',5'-tetramethyl[1',3',2']dioxaborolan-2'-yl)-10,20-diarylporphinato]zinc(II), with appropriately functionalized aryl and thienyl precursors. These donor-acceptor chromophores feature thiophenyl, [2,2']bithiophenyl, and [2,2';5',2' ']terthiophenyl units terminated with a 5-nitro group; one series of structures features these acceptor moieties appended directly to the porphyrin macrocycle meso-carbon position, while a second set utilizes an intervening meso-ethynyl moiety to modify porphyrin-to-thiophene conjugation. The dynamic hyperpolarizability of these compounds was determined from hyper-Rayleigh light scattering (HRS) measurements carried out at fundamental incident irradiation wavelengths (lambda(inc)) of 800 and 1300 nm; interestingly, measured beta(1300) values ranged from 650 --> 4350 x 10(-30) esu. The combined linear and nonlinear optical properties of these compounds challenge the classical concept of the nonlinearity/transparency tradeoff in charge-transfer chromophores: the magnitude of the molecular hyperpolarizability is observed to vary substantially despite approximately uniform ground-state absorptive signatures for a given porphyrin-to-thiophene linkage topology. These data show that these neutral dipolar molecules can express substantial beta(1300) values; such conjugated, electronically asymmetric porphyrin-thiophene chromophores may thus find utility for electrooptic applications at telecom-relevant wavelengths.

Journal Article↗
PubMed2002

Regiocontrolled synthesis of enantiopure 3,3'-thiosubstituted biphenyls.

Sulfenylation of 6,6'-dimethoxy-2,2'-dihydroxybiphenyl, used as a racemic mixture and single enantiomers, by phthalimidesulfenyl chloride afforded the corresponding 3,3'-N,N'-dithiophthalimide with complete regioselectivity. Simple manipulations of the latter compound allowed access to the corresponding bis-thiol or o-thioquinone as useful intermediates for the synthesis of new sulfur-containing open-chain and macrocyclic C(2) enantiopure ligands. The application of this methodology to the preparation of a biphenyl bearing two cysteine units as potential HIV-1 protease inhibitor is also described.

Journal Article↗
PubMed1997

New macrolactone of the desertomycin family from Streptomyces spectabilis.

The non-polyenic macrocyclic antibiotic complex 1012 was isolated from the culture broth of a strain Streptomyces spectabilis 1. The complex was found to belong to the desertomycin complex. Three main compounds of complex 1012 were separated and purified by preparative chromatographic methods. The identification was performed by UV, IR, NMR and mass-spectrometric studies. It was proved that two of the compounds with MW. 1191, C61H109NO21 and MW. 1190, C61H106O22 were identical to desertomycin A and D. The other com-pound with MW.1028, C55H96O17 is new macrolactone, named deser-tomycin E. The structures were established by detailed spectroscopic analysis.

Anti-Bacterial Agents↗
PubMed2004

4,4,6,6-Tetrachloro-2,2-(propylenedioxydi-o-phenylenediimino)-2lambda5,4lambda5,6lambda5-cyclotriphosphazene.

The title compound, C(15)H(16)Cl(4)N(5)O(2)P(3), is a cyclophosphazenic lariat (PNP-pivot) ether with a spiro-cyclic 12-membered macrocyclic ligand containing two ether O and two N atoms; the phosphazene ring is nearly planar. In the macrocyclic ring, there is a four-center (trifurcate) N-H.O/N-H.N hydrogen bond. The relative inner-hole size of the macrocycle is estimated as approximately 0.95 A.

Journal Article↗
PubMed2001

Molecular mechanisms by which iron induces nitric oxide synthesis in cultured proximal tubule cells.

Nitric oxide (NO) levels are increased after exposure of cultured proximal tubule cells (PTC) to non-haem iron, potentially contributing to PTC injury in disease states associated with increased iron exposure, including proteinuric renal disease. The mechanisms underlying this observed increase were investigated. After 3 h exposure to 400 microM nitrilotriacetate (NTA)-Fe, inducible nitric oxide synthase (iNOS) mRNA expression was significantly increased, with a corresponding increase in iNOS protein after 12 h. The nuclear binding activity of NFkappaB with 400 microM NTA-Fe was increased, and pyrrolidine dithiocarbamate (PDTC), an antioxidant inhibitor of NFkappaB, prevented both activation of NFkappaB and NO production in response to NTA-Fe. Inhibition of protein tyrosine kinase reduced iNOS mRNA, iNOS protein levels and NO production in response to NTA-Fe. The effect of tyrosine kinase inhibition on NFkappaB activation was variable, with herbimycin but not genistein having an inhibitory effect. Activation of either protein kinase A or C increased iNOS mRNA and protein levels, and NO production in response to NTA-Fe, whereas only the protein kinase C activator phorbol dibutyrate (PDBu) had a stimulatory effect on NFkappaB activation. The protein kinase A activator forskolin did not alter iron-induced activation of NFkappaB. These data suggest that the observed increase in NO production by PTC in response to iron is due to increased transcription of iNOS. The transcriptional regulation of this response is complex and involves NFkappaB, protein tyrosine kinase and the protein kinases A and C.

Animals↗
PubMed2003

Crystal structure of (1,10-phenanthroline-N,N')(1,4,7,10-tetraazacyclododecane-N,N',N",N"')nickel(II) diperchlorate.

The crystal structure of the title compound, [Ni(C8H20N4)(C12H8N2)](ClO4)2, has been determined by X-ray diffraction. The Ni(II) ion is six coordinated with four nitrogen atoms of the tetradentate macrocyclic ligand and two nitrogen atoms of the bidentate ligand in a distorted octahedron geometry. The folded tetradentate macrocyclic ligand adopts a configuration having four five-membered chelate rings in distorted eclipsed conformations. The four hydrogen atoms of the amine groups of the macrocyclic ligand are on the same side towards the bidentate ligand.

Journal Article↗
PubMed2003

Self-assembly of dialkyltin(IV) moieties and aromatic dicarboxylates to complexes with a polymeric or a discrete trinuclear macrocyclic structure in the solid state and a mixture of fast interchanging cyclooligomeric structures in solution.

It is well-known that the structures of trialkyltin(IV) carboxylates can be either monomeric, polymeric, or cyclooligomeric in the solid state. In contrast, all dialkyltin(IV) dicarboxylates characterized so far in the solid state have monomeric or polymeric structures, however, for some cases it has been proposed that their solution-state structure is cyclooligomeric. In order to generate more information on this subject, dimethyl- and di-n-butyltin(IV) complexes with phthalic and isophthalic acid have been prepared and analyzed both in solution and in the solid state. The solid-state structures of the two dialkyltin(IV) phthalates examined herein contain polymeric molecular chains, however, with supramolecular Sn.O' interactions, which result in the generation of cyclooligomeric units. This provides evidence for the presence of discrete cyclooligomeric structures in solution, which are involved in fast dynamic exchange equilibria as evidenced by (1)H, (13)C, and (119)Sn NMR spectroscopy. In the case of the two dialkyltin(IV) isophthalate complexes studied herein (R = Me, n-Bu), only the di-n-butyltin derivative is soluble and NMR spectroscopy as well as FAB(+) spectrometry indicates the formation of cyclic dinuclear, trinuclear, and/or tetranuclear species in solution, which may be involved also in fast dynamic exchange equilibria. In the solid state, however, discrete cyclotrinuclear units can be identified, in which the 24-membered macrocyclic cavity is almost completely planar, having six oxygen atoms directed into its interior and six Sn-n-butyl groups approximately perpendicular to the molecular plane. The diameter of the cyclic cavity can be described by the transannular O.O distances that vary from 7.68 to 7.84 A, being large enough for the introduction of linear alkyl groups. This can be demonstrated by the supramolecular structure of this compound, which contains a new type of bis[2]pseudorotaxane formed between two molecules through mutual threading via two of the Sn-butyl groups. Such a supramolecular entity has been unknown so far, since the usual composition of bis[2]pseudorotaxanes is the trimolecular combination of a macrocyclic ring system with two threads.

Journal Article↗
PubMed1992

Effect of herbimycin A, an antagonist of tyrosine kinase, on bcr/abl oncoprotein-associated cell proliferations: abrogative effect on the transformation of murine hematopoietic cells by transfection of a retroviral vector expressing oncoprotein P210bcr/abl and preferential inhibition on Ph1-positive leukemia cell growth.

Herbimycin A, a benzoquinoid ansamycin antibiotic, was demonstrated to decrease intracellular phosphorylation by protein tyrosine kinase (PTK). In Philadelphia chromosome (Ph1)-positive leukemias such as chronic myelogenous leukemia (CML) and Ph1-positive acute lymphoblastic leukemia (ALL), both of which express bcr-abl fused gene products (P210bcr-abl or P190bcr-abl protein kinase) with augmented tyrosine kinase activities, herbimycin A markedly inhibited the in vitro growth of the Ph1-positive ALL cells and the leukemic cells derived from CML blast crisis. However, the same dose of herbimycin A did not inhibit in vitro growth of a broad spectrum of Ph1-negative human leukemia cells, and several other protein kinase antagonists also displayed no preferential inhibition. Furthermore, we demonstrated that herbimycin A has an antagonizing effect on the growth of transformed cells by a transfection of retroviral amphotrophic vector expressing P210bcr/abl into a murine interleukin (IL)-3-dependent myeloid FDC-P2 cell line. This inhibition was abrogated by the addition of sulfhydryl compounds, similar to the reaction previously described for Rous sarcoma virus transformation. The inhibitory effect of herbimycin A on the growth of Ph1-positive cells was associated with decreased bcr/abl tyrosine kinase activity, but no decrease of bcr-abl mRNA and protein, suggesting that the inactivation of bcr-abl tyrosine kinase activity by herbimycin A may be induced by its binding to the bcr-abl protein portion that is rich with sulfhydryl groups. The present study indicates that herbimycin A is a beneficial agent for the investigation of the role of the bcr-abl gene in Ph1-positive leukemias and further suggests that the development of agents inhibiting the bcr-abl gene product may offer a new therapeutic potential for Ph1-positive leukemias.

Benzoquinones↗
PubMed2000

Oligonucleotide conjugates of Eu(III) tetraazamacrocycles with pendent alcohol and amide groups promote sequence-specific RNA cleavage.

Eu(III) complexes of two neutral bifunctional tetraaaza macrocyclic ligands ¿1-[1-carboxamido-3-(4-nitrophenyl)propyl]-4,7,10-tris(2-hydroxyethyl)-1 ,4,7,10-tetraazacyclododecane and 2-(4-nitrobenzyl)-1,4,7,10-tetrakis(2-hydroxyethyl)-1,4,7,10-tetraaza cyclododecane¿ are prepared. Eu(III) complexes of the isothiocyanate derivatives of these macrocycles are treated with oligonucleotides containing 2'-O-propyl-amine linkers to form conjugates. Hydrolytic cleavage of an oligoribonucleotide is promoted by Eu(III) macrocyclic oligonucleotide conjugates containing complementary (antisense) sequences. Cleavage is not observed in the presence of Eu(III) conjugates containing scrambled sequences nor by free complex. Despite the fact that one of the free macrocyclic complexes is more reactive than the other, the extent of cleavage observed is similar for conjugates containing either Eu(III) macrocyclic complex.

Alcohols↗
PubMedDate not supplied

Comparison of yttrium and indium complexes of DOTA-BA and DOTA-MBA: models for (90)Y- and (111)In-labeled DOTA-biomolecule conjugates.

Yttrium and indium complexes of 1,4,7,10-tetraaza-4,7,10-tris(carboxymethyl)-1-cyclododecylacetylbenzylamine (DOTA-BA) and 1,4,7,10-tetraaza-4,7,10-tris(carboxymethyl)-1-cyclododecylacetyl-R-(+)-alpha-methylbenzylamine (DOTA-MBA) were prepared in order to study solution structures of (90)Y- and (111)In-labeled DOTA-biomolecule conjugates. (90)Y and (111)In complexes M(L) (M = (90)Y and (111)In; L = DOTA-BA and DOTA-MBA) were prepared from the reaction of MCl(3) with DOTA-BA and DOTA-MBA, respectively, in ammonium acetate buffer. A reverse phase HPLC method revealed that both (90)Y and (111)In complexes show only one radiometric peak in their radio-HPLC chromatograms. It was also found that (111)In(DOTA-BA) and (111)In(DOTA-MBA) are more hydrophilic than their corresponding (90)Y analogues, suggesting different coordination spheres in (111)In and (90)Y complexes of the same DOTA conjugate. Complexes M(L) (M = Y and In; L = DOTA-BA and DOTA-MBA) were prepared and characterized by HPLC, LC-MS, and NMR ((1)H and (13)C) methods. The HPLC concordance experiments for (90)Y(DOTA-MBA)/Y(DOTA-MBA) and (111)In(DOTA-MBA)/In(DOTA-MBA) show that the same complex is prepared at both tracer and macroscopic levels. The NMR data ((1)H and (13)C) clearly demonstrates that Y(DOTA-BA) and Y(DOTA-MBA) exist in solution as one predominant isomer. VT NMR data ((1)H and (13)C) show that In(DOTA-BA) and In(DOTA-MBA) are fluxional at room temperature while Y(DOTA-BA) and Y(DOTA-MBA) become fluxional only at elevated temperatures. The fluxionality of these complexes is due to rapid rotation of acetate/acetamide chelating arms and inversion of ethylenic groups of the macrocyclic ring.

Chelating Agents↗
PubMed2003

Synthetic studies toward sarain A. Formation of the western macrocyclic ring.

Starting with the tricyclic core 2b, annulation to form the 13-membered western ring of sarain A has been achieved to afford the macrocycle 30a by initial construction of the sterically congested quaternary center at C-3, followed by elaboration of the C-3 side-chain and ring-closing olefin metathesis. Also included is a parallel conversion of tricycle 2c to macrocycle 30b containing a functionalized side-chain at N-1 suitable for attachment of the eastern macrocyclic ring.

Alkaloids↗
PubMed2000

A photochemically driven molecular-level abacus

A molecular-level abacus-like system driven by light inputs has been designed in the form of a [2]rotaxane, comprising the pi-electron-donating macrocyclic polyether bis-p-phenylene-34-crown-10 (BPP34C10) and a dumbbell-shaped component that contains 1) a Ru(II) polypyridine complex as one of its stoppers in the form of a photoactive unit, 2) a p-terphenyl-type ring system as a rigid spacer, 3) a 4,4'-bipyridinium unit and a 3,3'-dimethyl-4,4'-bipyridinium unit as pi-electron-accepting stations, and 4) a tetraarylmethane group as the second stopper. The synthesis of the [2]rotaxane was accomplished in four successive stages. First of all, the dumbbell-shaped component of the [2]rotaxane was constructed by using conventional synthetic methodology to make 1) the so-called "west-side" comprised of the Ru(II) polypyridine complex linked by a bismethylene spacer to the p-terphenyl-type ring system terminated by a benzylic bromomethyl function and 2) the so-called "east-side" comprised of the tetraarylmethane group, attached by a polyether linkage to the bipyridinium unit, itself joined in turn by a trismethylene spacer to an incipient 3,3'-dimethyl-4,4'-bipyridinium unit. Next, 3) the "west-side" and "east-side" were fused together by means of an alkylation to give the dumbbell-shaped compound, which was 4) finally subjected to a thermodynamically driven slippage reaction, with BPP34C10 as the ring, to afford the [2]rotaxane. The structure of this interlocked molecular compound was characterized by mass spectrometry and NMR spectroscopy, which also established, along with cyclic voltammetry, the co-conformational behavior of the molecular shuttle. The stable translational isomer is the one in which the BPP34C10 component encircles the 4,4'-bipyridinium unit, in keeping with the fact that this station is a better pi-electron acceptor than the other station. This observation raises the question- can the BPP34C10 macrocycle be made to shuttle between the two stations by a sequence of photoinduced electron transfer processes? In order to find an answer to this question, the electrochemical, photophysical, and photochemical (under continuous and pulsed excitation) properties of the [2]rotaxane, its dumbbell-shaped component, and some model compounds containing electro- and photoactive units have been investigated. In an attempt to obtain the photoinduced abacus-like movement of the BPP34C10 macrocycle between the two stations, two strategies have been employed-one was based fully on processes that involved only the rotaxane components (intramolecular mechanism), while the other one required the help of external reactants (sacrificial mechanism). Both mechanisms imply a sequence of four steps (destabilization of the stable translational isomer, macrocyclic ring displacement, electronic reset, and nuclear reset) that have to compete with energy-wasteful steps. The results have demonstrated that photochemically driven switching can be performed successfully by the sacrificial mechanism, whereas, in the case of the intramolecular mechanism, it would appear that the electronic reset of the system is faster than the ring displacement.

Journal Article↗
PubMed2001

Synthesis of nickel(II) triazolenaphthalocyanine and related macrocycles.

The synthesis of novel monbenzotriazolephthalocyanines (3-6), low-symmetry phthalocyanine analogues, is described for the first time using a novel and simple stepwise strategy which involves the use of substituted naphthalodinitriles 8-11 and appropriately substituted three-unit compounds such as 7. Belonging to the same family, compound 1, which we have called triazolenaphthalocyanine, has been prepared by a statistical method from compound 2 and 3,5-diamino-1,2,4-triazole. Compound 1 shows a bathochromic shift of the Q-band in UV-vis spectrum due to the fusing of benzene rings to the triazolephthalocyanine core.

Journal Article↗
PubMedDate not supplied

New macrocyclic trichothecenes from Baccharis megapotamica.

The isolation and structural elucidation of biologically active baccharinoids B1 [11a], B2 [12a], B3 [5a], and B7 [6a] are reported with crystal structure determinations of baccharinoid B7 and of the triacetate of baccharinoid B2. All four compounds are isomeric with 11a/12a and 5a/6a being epimeric at C13'.

Brazil↗
PubMed2004

Determination of enantiomeric compositions of pharmaceutical products by near-infrared spectrometry.

A new method for the determination of enantiomeric compositions of a variety of drugs including propranolol, atenolol, and ibuprofen has been developed. The method is based on the use of the near-infrared technique to measure diastereomeric interactions between an added carbohydrate compound and both enantiomeric forms of a drug followed by evaluation of the data by partial least square analysis. The fact that the method works well with all three macrocyclic carbohydrates with different cavity sizes (i.e., alpha-, beta-, and gamma-cyclodextrin) and with sucrose, which is a linear carbohydrate, clearly demonstrates that it is not necessary to have inclusion complex formation to produce effective diastereomeric interactions. Rather a simple adsorption of the drug onto a carbohydrate is sufficient. Since inclusion complex formation is not a requisite, this method is not limited to the three drugs evaluated in this study but is rather universal as it can, in principle, be used for the sensitive and accurate determination of enantiomeric compositions of many different types of drugs with only about 1.5mg/mL concentration and enantiomeric excess as low as 0.80%, in water or in a mixture of water with organic solvent. Furthermore, it does not rely on the use of rather expensive carbohydrates such as cyclodextrins but is equally as effective even with a simple and inexpensive carbohydrate such as sucrose.

Atenolol↗
PubMedDate not supplied

Facile macrocyclizations to beta-turn mimics with diverse structural, physical, and conformational properties.

On-resin S(N)Ar reactions were performed to prepare the macrocyclic beta-turn mimics 1a-n (Scheme 1 and Table 1). These reactions occurred more efficiently than completely analogous macrocyclization reactions that do not involve an iodinated aromatic electrophile. The synthesis was also modified to allow introduction of an alkyne via a solid-phase Sonogashira reaction (giving compound 2, Scheme 2) and an aryne via a solid-phase Suzuki reaction (giving compound 3, Scheme 2). Conformational analyses of three illustrative compounds, i.e., 1i, 2, and 3, were performed using a combination of NMR, circular dichroism, and computer-aided molecular simulation methods. Overall, the preferred conformations of all three molecules tended to be type-I-like beta-turns, but for compound 3 interaction of the electron cloud of the aryl substituent with the oxygen lone pairs seems to cause differences in the preferred orientation of the turn frameworks. This study illustrates how iodinated electrophiles can be used in solid-phase S(N)Ar reactions to increase the molecular and conformational diversity in a library.

Alkynes↗
PubMed2005

Electrochemistry, spectroelectrochemistry, chloride binding, and O2 catalytic reactions of free-base porphyrin-cobalt corrole dyads.

Three face-to-face linked porphyrin-corrole dyads were investigated as to their electrochemistry, spectroelectrochemistry, and chloride-binding properties in dichloromethane or benzonitrile. The same three compounds were also investigated as to their ability to catalyze the electroreduction of dioxygen in aqueous 1 M HClO4 or HCl when adsorbed on a graphite electrode. The characterized compounds are represented as (PCY)H2Co, where P = a porphyrin dianion; C = a corrole trianion; and Y = a biphenylenyl, 9,9-dimethylxanthenyl, or anthracenyl spacer, which links the two macrocycles in a face-to-face arrangement. An axial binding of one or two Cl- ligands to the cobalt center of the corrole is observed for singly and doubly oxidized (PCY)H2Co, with the exact stoichiometry of the reaction depending upon the spacer size and the concentration of Cl- added to solution. No Cl- binding occurs for the neutral or reduced forms of the dyad, which contrasts with what is seen for the monocorrole, (Me4Ph5Cor)Co, where a single Cl- ligand is added to the Co(III) corrole in PhCN. The Co(III) form of the corrole in (PCY)H2Co also appears to be the catalytically active species in the electroreduction of dioxygen, which occurs at potentials associated with the Co(IV)/Co(III) reaction, that is, 0.35 V in 1 M HClO4 as compared to 0.31-0.42 V for the same three dyads in PhCN and 0.1 M TBAP. The potential for the catalytic electroreduction of O2 in HCl shifts negatively by 60 to 70 mV as compared to E(1/2) values in 1 M HClO4, consistent with the binding of Cl- to the Co(IV) form of the corrole and its rapid dissociation after electroreduction to Co(III) at the electrode surface.

Journal Article↗