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At least 127 records · Page 7Linked to original sources
PubMed2002

Synthesis of unsymmetrical aroyl acyl imides by aminocarbonylation of aryl bromides.

Aroyl imides were prepared by a palladium-catalyzed aminocarbonylation reaction of aryl bromides with carbon monoxide and primary amides in good yields (58-72%). The reactions were carried out under mild conditions (5 bar, 120 degrees C) using 1 mol % of a palladium phosphine complex. Several aryl bromides were reacted with formamide, acetamide, benzamide, and benzenesulfonamide, respectively. For activated aryl bromides, a phosphine-to-palladium ratio of 2:1 was sufficient, but less reactive aryl bromides required a ligand-to-palladium ratio of 6:1 in order to stabilize the catalyst and achieve full conversion. The imides were very sensitive to aqueous basic conditions and were easily converted to aroyl amides or benzoic acids.

Journal Article↗
PubMed2003

Merocyanine dyes containing imide functional groups: synthesis and studies on hydrogen bonding to melamine receptors.

The condensation of the CH acidic heterocycles 4-alkyl-2,6-dioxo-1,2,5,6-tetrahydropyridine-3-carbonitrile (5a and b) and barbituric acid (15) with electron-rich thiophene aldehydes and benzaldehyde derivatives affords the respective monomethine dyes 10-13 and 17-19. The formylation of 5a,b and 15 with N,N'-diphenylformamidine or dibutylformamide in acetic anhydride and further reaction with 4-picolinium salts 9a,b provide the dimethine dyes 14 and 20a,b. Triple hydrogen bonding of the imide groups of merocyanine dyes 10-14 has been investigated by NMR titration experiments with melamine 21. Despite rather pronounced variations of the charge-transfer properties within the given series of dyes, minor changes of their binding constants have been observed. These results could be rationalized by semiempirical calculations that reveal small changes in the charge density at the oxygen functionalities involved in hydrogen bonding upon variation of the electron-donating carbocyclic or heterocyclic groups at the terminal double bond. Although the binding constants for triple hydrogen bonding between imides and melamines are rather weak in chloroform, they proved to be strong enough to facilitate dissolution of some of these dyes in aliphatic solvents by coordination to amphiphilic melamines and dipolar aggregation. UV-vis spectral changes observed in methylcyclohexane vs chloroform suggest the formation of colloidal assemblies through noncovalent polymerization.

Hydrogen Bonding↗
PubMed1999

Titanium-Mediated Cyclization of omega-Vinyl Imides in Alkaloid Synthesis: Isoretronecanol, Trachelanthamidine, 5-Epitashiromine, and Tashiromine.

A new method for the stereocontrolled synthesis of pyrrolizidine and indolizidine alkaloids by means of titanium-mediated cyclization of omega-vinyl imides is described. The general procedure involves treatment of readily available omega-vinyl imides 9 and 10 with 2.5 equiv of cyclopentylmagnesium chloride in the presence of ClTi(O-i-Pr)(3) (1.1 equiv) and subsequent stereoselective reduction of the N-acylaminal group. The cis and trans ring junction stereoisomers can be stereoselectively prepared by catalytic hydrogenation (H(2), PtO(2), EtOAc) and NaCNBH(3) reduction (TFA, MeOH), respectively. Finally, treatment of the resulting lactams with LAH or diborane afforded the target alkaloids 1-8 in good yields.

Journal Article↗
PubMed2000

Fe(II)-catalyzed imidation of allyl sulfides and subsequent

Allyl aryl sulfides 1 and 5 were shown to undergo an imidation/[2,3]-sigmatropic rearrangement reaction upon treatment with N-tert-butyloxycarbonyl azide (BocN3) and catalytic amounts of FeCl2 in CH2Cl2. The N-Boc-protected N-allyl sulfenamides 3 and 21 were obtained in yields between 48 and 75% (12 examples). Whereas the reaction is well suited for the transformation of alpha-unbranched sulfides to alpha-branched sulfenamides, the enantiomerically pure alpha-branched sulfides 10 and 13 reacted sluggishly. The corresponding sulfenamides 22 and 23 were obtained in only moderate enantiomeric excess (36-39% ee). A reaction mechanism is proposed that postulates the intermediacy of an N-Boc-substituted Fe(IV)-nitrene complex 14 acting as the imidation reagent in the catalytic cycle. Possible side reactions are discussed. The benzenesulfenamides 3 were further converted into N-Boc-N-allylamines 4 by removal of the phenylsulfanyl group. Bu3SnH in benzene was found to be the reagent of choice for the deprotection of alpha-branched amines that bear a secondary allyl substituent (five examples, 71-93% yield). This method failed for the alpha-branched amines 3i-k with a tertiary allyl substituent. The phenylsulfanyl group was finally removed with P(OEt)3/NEt3 in CH2Cl2 (three examples, 43-62% yield).

Journal Article↗
PubMed2003

Glycosylation of N-acetylglucosamine: imidate formation and unexpected conformation.

[structure: see text] Rhamnosylation in mild conditions of a disaccharide containing N-acetylglucosamine afforded the imidate 6 while at higher temperature and concentration of promoter trisaccharide 7 was isolated. The kinetic imidate 6 was independently rearranged in 50% yield to the thermodynamic trisaccharide 7. Comparative NMR studies of 7 in CDCl(3) and DMSO-d(6) suggest the formation of a nonchair conformation in CDCl(3). The structure of 7 was confirmed through the independent synthesis of the N-acetylacetamido trisaccharide 11.

Acetylglucosamine↗
PubMed2005

Synthesis of new organic super acids-N-(trifluoromethylsulfonyl)imino derivatives of trifluoromethanesulfonic acid and bis(trifluoromethylsulfonyl)imide.

Salts of N-trifluoromethylsulfonyl derivatives of trifluoromethyl- and phenylsulfonimidoyl imides have been synthesized by two different routes. Both methods are one-pot reactions, that run in mild conditions with good yields. Two novel organic super acids: bis[N-(trifluoromethylsulfonyl)trifluoromethanesulfonimidoyl]imide and N,N'-bis(trifluoromethyl-sulfonyl)diimino trifluoromethanesulfonic acid were prepared and the structure of their potassium salts was obtained by single-crystal X-ray diffraction.

Journal Article↗
PubMed2005

Cyclic and acyclic sulfonimides in reactions with Rh(II)-ketocarbenoids: a new access to chemoselective O-functionalization of the imidic carbonyl groups.

Catalytic decomposition of diazoacetylacetone, diazoacetoacetic, diazomalonic, and diazoacetic esters using dirhodium tetraacetate in the presence of isothiazol-3(2H)-one 1,1-dioxides and a number of N-(arenesulfonyl)carboxamides in solutions of methylene chloride or dichloroethane gives rise to O-alkylation of the imidic carbonyl groups by Rh(II)-carbenoids and the formation of O-alkylimidates as the final products. The reaction proceeds with high chemoselectivity via carbonyl ylides and offers a powerful method for the synthesis in good yields of the imidates with polyfunctional O-alkyl groups. On the basis of X-ray analysis and 1H- and 13C-NMR studies it was shown that the resulting acyclic O-alkylimidates have the E-configuration in the solid state and in solution. Unlike acyclic analogues, the cyclic carbonyl ylide derived from substituted diazosaccharin by intramolecular cyclization of the appropriate diketocarbenoid is capable of reacting with DMAD in a 1,3-cycloaddition process.

Journal Article↗
PubMed1976

Effects of dicyclohexylcarbodi-imide on proton translocation coupled to fumarate reduction in anaerobically grown cells of Escherichia coli K-12.

The addition of dicyclohexylcarbodi-imide to anaerobic cells of Escherichia coli K12 decreases both the observed extent of proton translocation coupled to fumarate reduction by endogenous substrates and the t 1/2 of proton re-entry after such translocation, but does not affect fumarate uptake. Dicyclohexylcarbodi-imide also inhibits fumarate reductase activity in cell extracts.

Anaerobiosis↗
PubMed1982

Proton translocation by the mitochondrial cytochrome b-c1 complex is inhibited by NN'-dicyclohexylcarbodi-imide.

NN'-Dicyclohexylcarbodi-imide at low concentrations decreases the H+/2e ratio for rat liver mitochondria over the span succinate to oxygen from 5.9 +/- 0.3 (mean +/- S.E.M.) to 4.0 +/- 0.1 and for the cytochrome b-c1 complex from 3.8 +/- 0.2 to 1.9 +/- 0.1, but has little effect on the H+/2e ratio of cytochrome oxidase. The decrease in stoicheiometry is due, not to uncoupling or inhibition of electron transport, but to inhibition of proton translocation. NN'-Dicyclohexylcarbodi-imide thus 'decouples' proton translocation in the cytochrome b-c1 complex.

Animals↗
PubMed1983

Inhibition of nicotinamide nucleotide transhydrogenase in rat liver submitochondrial particles by dicyclohexylcarbodi-imide and butanedione.

Nicotinamide nucleotide transhydrogenase in rat liver submitochondrial particles is inhibited by treatment with NN'-dicyclohexylcarbodi-imide or butane-2,3-dione. Both inhibitions are pseudo-first-order with respect to enzyme activity. The reaction order with respect to inhibitor is close to unity for butanedione, but is significantly lower than unity for dicyclohexylcarbodi-imide.

Animals↗
PubMed1987

Some electron-transfer reactions involving carbodi-imide-modified cytochrome c.

The reaction kinetics of native and carbodi-imide-modified tuna and horse heart cytochromes c with both a strong (dithionite) and a relatively weak (ascorbate) reducing agent were studied over a wide range of conditions. In their reactions with dithionite both the native and modified cytochromes exhibit single exponential time courses. The effects of dithionite concentration and ionic strength on the rate of the reduction are complex and can best be explained in terms of the model proposed by Lambeth & Palmer [(1973) J. Biol. Chem. 248, 6095-6103]. According to this model, at low ionic strength the native proteins are reduced almost exclusively by S2O4(2-) whereas the modified proteins showed reactivity towards both S2O4(2-) and SO2.-. These findings are interpreted in terms of the different charge characteristics of the carbodi-imide-modified proteins relative to the native proteins. The findings that the modified proteins react with ascorbate in a biphasic manner are explained as arising from ascorbate binding to a reducible form of the protein, before electron transfer, with an equilibrium between the ascorbate-reducible form of the protein and a non-reducible form. Estimates were obtained for both the ascorbate equilibrium binding constant and the rate constant for the internal electron transfer for both the native and modified horse and tuna proteins. The effect of pH on the reactions indicates that the active reductant in all cases is ascorbate2-. The studies of ascorbate reactivity yield important information concerning the proposed correlation between ascorbate reducibility and the presence of a 695 nm-absorption band, and the study of dithionite reactivity illustrates the effect of protein charge and solution ionic strength on the relative contributions made by the species SO2.- and S2O4(2-) to the reduction of ferricytochrome c.

Animals↗
PubMed1991

Some reactions of carbon monoxide and oxygen with carbodi-imide-modified cytochrome c.

The reactivity of carbodi-imide-modified tuna and horse heart cytochromes c with the ferrous ion ligands CO and O2 has been studied. Both modified cytochromes bind one molecule of CO. Stopped-flow and flash-photolysis experiments indicate the presence of three kinetic processes in the reaction of the cytochromes with CO. The second-order rate constants associated with all three kinetic process are pH-independent being 2.8 x 10(5) M-1.s-1, 3.8 x 10(4) M-1.s-1 and 4 x 10(3) M-1.s-1 under all conditions studied. The concentration-dependence of the contributions made by each of the processes to the overall absorbance change indicates that the fast and slow kinetic phases are associated with two forms of the cytochromes which are in equilibrium, whereas the intermediate phase arises from a separate cytochrome species. The quantum yield for the photodissociation of CO from the ferrous cytochromes is unusually low. Both modified cytochromes are capable of binding and reducing O2. In the presence of excess reductant, the modified cytochromes can catalytically reduce large molar excesses of O2. In the absence of excess reducing agent, the oxy complex initially formed undergoes a pH-dependent intramolecular electron-transfer process with half-life approx. 10 min. EDC [1-ethyl-3-(3-dimethylaminopropyl)carbodi-imide]-promoted internal cross-linking is proposed to account for differences between the EDC-modified proteins and carboxymethylated cytochrome c.

Animals↗
PubMed2006

Photodegradation of polymer-dispersed perylene di-imide dyes.

Polymer-dispersed perylene di-imide dye photodegradation is investigated by monitoring the fluorescence intensity as a function of 532 nm laser pulses. Anaerobically irradiated polymer-dye films exhibited an accelerated decrease in fluorescence intensity, which was partially recovered upon exposure to oxygen. Decelerated photodegradation rates were observed for perylene di-imide ethanol solutions upon the addition of a singlet oxygen quenching antioxidant. These observations suggest reversible photoreduction and type II photo-oxidation as important photodegradation mechanisms. Type II photo-oxidation for perylene red 532 nm irradiation is supported by a singlet oxygen quantum yield of 0.09+/-0.03, determined via detection of time-resolved O2 (a1delta(g) --> X3sigma(g)-) infrared phosphorescence.

Journal Article↗
PubMed2004

Electroneutrality coupling of electron transfer at an electrode surface and ion transfer across the interface between thin-layer of 1-octyl-3-methylimidazolium bis(perfluoroalkylsulfonyl)imide covering the electrode surface and an outer electrolyte solution.

The electrode reaction of decamethylferrocene (DMFc) dissolved in a thin layer of a room-temperature molten salt (RTMS), 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C8mimC1C1N) or 1-octyl-3-methylimidazolium bis(pentafluoroethylsulfonyl)imide (C8mimC2C2N), on a self-assembled monolayer-modified gold electrode is coupled with the ion transfer across the interface between the RTMS and the outer aqueous solution (W) to give a voltammogram whose shape resembles a voltammogram of a simple one-electron transfer process. The electroneutrality of the RTMS layer during the oxidation of DMFc to decamethylferricenium ion is maintained by the concomitant dissolution of C8mim+ ion from the RTMS phase to the W phase, and the reduction of decamethylferricenium ion to DMFc is accompanied by the transfer of either C1C1N- or C2C2N- from RTMS to W. The midpoint potential of the voltammogram varies with the concentration of the salt in the aqueous phase, C8mimCl or LiCnCnN (n = 1 or 2), in a Nernstian manner, showing that the phase-boundary potential between the RTMS and the W is controlled by the partition of these ions. Although the phase-boundary potential across the RTMS / W interface is Nernstian with respect to the ions common to both phases at the equilibrium, the polarization at the RTMS / W interface under current flow distorts the shape of the voltammograms, resulting in a wider peak separation in the voltammogram.

Journal Article↗
PubMed2006

Immunomodulatory drugs (IMiDs): a new treatment option for myelodysplastic syndromes.

The IMiDs represent a new proprietary class of thalidomide analogues that possess greater potency and less toxicity than the parent compound. As a group, these agents share the pharmacologic property of modulating cellular response to ligand activation, the precise biologic effect of which is cell lineage and stimulant-dependent. Lenalidomide (CC-5013; Revlimid), a second generation IMiD, has shown significant erythropoietic activity in patients with lower risk MDS that have failed or are not candidates for recombinant erythropoietin treatment. Unlike cytokine therapy, lenalidomide suppresses select MDS clones and enhances erythropoietin receptor signaling to restore erythropoiesis. Activity is greatest in patients with interstitial deletions involving chromosome 5q31.1. A multicenter phase II study reported a 76 % overall transfusion response rate in transfusion-dependent patients with deletion 5q, with 67 % achieving transfusion independence after a median interval of 4.6 weeks of treatment. Cytogenetic responses were observed in 73% of patients with complete cytogenetic remission in 45% patients. Both transfusion response and cytogenetic response frequency were independent of karyotype complexity, raising excitement that this new treatment strategy might favorably alter the natural history of disease in higher risk patients with deletion 5q. Lenalidomide was approved by the U.S. Food and Drug Administration on December 27, 2005, for the treatment of IPSS Low and intermediate-1 risk MDS patients with del(5q) abnormality. A phase III Intergroup trial (ECOG 2905) will test the capacity to potentiate erythropoietin response by comparing response to lenalidomide monotherapy to the combination of darbepoetin and lenalidomide in non-deletion 5q MDS patients.

Drug Delivery Systems↗
PubMed1994

Acute toxic and teratogenic effects of cyclic imides in rodents.

Four structurally different cyclic imides or related derivatives (o-(N-phthalimido)acetophenone (1), 2,3-dihydrophthalazine-1,4-dione (2), N-(4-methylphenyl)diphenamide (3), and 4,6-dihydro-5H-dibenz[c,e]azepine (4) were examined for acute toxicity in mice at multiple doses, for long term toxicity at a single dose in rats, and for deleterious effects on fertility and pup development in rodents. No deleterious effects were observed when mice were administered agents at 20, 50, and 100 mg/kg/day for seven days. All other measured characteristics and values were normal for the four compounds. The principle effect of the compounds was to reduce the percent pregnancies in treated mice compared to the controls. Compound 2 afforded the greatest reduction of pregnancy (54%) at 100 mg/kg/day. Compounds 3 and 4 caused a minor reduction in pregnancy (12-20%). The compounds did not appear to cause measureable teratogenic effects; pups of treated rodents thrived and survived as well as controls. There were no effects on murine male fertility when compounds were administered at 20, 50, and 100 mg/kg/day for six weeks.

Animals↗
PubMed2006

A practical ruthenium-catalyzed cleavage of the allyl protecting group in amides, lactams, imides, and congeners.

A convenient methodology for the deprotection of N-allylic amide-like moieties was developed. The first examples accounting for the ruthenium-catalyzed deallylation of amides, lactams, imides, pyrazolidones, hydantoins, and oxazolidinones have been achieved by the sequential use of Grubbs carbene (isomerization step) and RuCl(3) (oxidation step). A variety of substrates, including enantiopure multifunctional beta- and gamma-lactams, can be employed.

Allyl Compounds↗
PubMed1981

Effects of imide analogs on enzymes required for cholesterol and fatty acid synthesis.

Twelve imide analogs were examined for their ability to lower serum cholesterol and triglyceride levels in mice. Potent activity was observed for compounds containing a phthalimide or saccharin ring structure. The ability to lower serum cholesterol appears to be related to the ability to suppress acetyl-CoA synthetase activity. The availability of acetyl-CoA in the cytoplasm is a key regulatory component for cholesterol and fatty acid synthesis. The capacity to reduce serum triglycerides was related directly to the ability of the compound to inhibit acetyl-CoA carboxylase activity, the regulatory enzyme of fatty acid synthesis.

Acetate-CoA Ligase↗