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PubMed1999

Aziridination of Activated Imines with Monocarbonyl Iodonium Ylides Generated from (Z)-(2-Acetoxyvinyl)iodonium Salts via Ester Exchange: Stereoselective Synthesis of 2-Acylaziridines.

Monocarbonyl iodonium ylides, generated in situ from (Z)-(2-acetoxyvinyl)iodonium salts via an ester exchange reaction with EtOLi, undergo alkylidene transfer reactions to activated imines yielding 2-acylaziridines in good yields. The stereochemical outcome of this aziridination was shown to be dependent on both the activating groups of the imines and the reaction solvents: that is, the aziridination of N-(2,4,6-trimethylbenzenesulfonyl)imines in THF affords cis-aziridines as a major product while that of N-benzoylimines in THF-DMSO or THF gives the trans isomer stereoselectively.

Journal Article↗
PubMed2002

Stepwise radial complexation of imine groups in phenylazomethine dendrimers.

Dendrimers are highly branched organic macromolecules with successive layers or 'generations' of branch units surrounding a central core. Organic-inorganic hybrid versions have also been produced, by trapping metal ions or metal clusters within the voids of the dendrimers. The unusual, tree-like topology endows these nanometre-sized macromolecules with a gradient in branch density from the interior to the exterior, which can give rise to an energy gradient that directs the transfer of charge and energy from the dendrimer periphery to its core. Here we show that tin ions, Sn(2+), complex to the imine groups of a spherical polyphenylazomethine dendrimer in a stepwise fashion. This behaviour reflects a gradient in the electron density associated with the imine groups, with complexation in a more peripheral generation proceeding only after complexation in generations closer to the core has been completed. By attaching an electron-withdrawing group to the dendrimer core, we are able to change the complexation pattern, so that the core imines are complexed last. By further extending this strategy, it should be possible to control the number and location of metal ions incorporated into dendrimer structures, which might find uses as tailored catalysts or building blocks for advanced materials.

Journal Article↗
PubMed1984

Carbonyl oxygen exchange evidence of imine formation in the glutamate dehydrogenase reaction and identification of the "occult role" of NADPH.

Although an imine intermediate has long been postulated as participating in the reaction catalyzed by glutamate dehydrogenase (EC 1.4.1.4), direct evidence for a kinetically competent intermediate of this kind has not heretofore been found. We have sought such evidence by studying the exchange of the carbonyl oxygen atom of alpha-ketoglutarate in a variety of binary, ternary, and quaternary enzyme complexes. We have found that the time course of this exchange is biphasic when the enzyme, alpha-ketoglutarate, NADPH, and ammonia are all present initially and that the rapid initial phase ends when ammonia is depleted. We present evidence that this rapid exchange is due to an imine form of the enzyme-reduced-coenzyme-substrate-ammonia complex. Formed very rapidly but in very small amounts, this imine can undergo one of two competing fates: (i) hydrolytic reversal to form carbonyl-exchanged alpha-ketoglutarate with regeneration of ammonia, and (ii) an internal hydride transfer converting the iminoglutarate to glutamate, whereby ammonia is consumed. The agreement of the amplitudes of rapid 18O exchange with predictions based on direct transient-state spectroscopic kinetic studies supports the identity of an enzyme-NADPH-alpha-iminoglutarate complex as an obligatory intermediate on the enzyme-catalyzed reaction path. The corresponding enzyme-alpha-iminoglutarate binary complex (previously suggested as an intermediate) is formed at a rate that is less than 1/1000th of that of the NADPH-containing complex shown here, and it therefore lacks kinetic competence. This finding points up an important catalytic role for NADPH that does not involve its obvious function as a hydride donor and is distinctly separate from this role. In the case of the glutamate dehydrogenase-catalyzed reaction, this "occult role" clearly involves the induction of ketimine formation on the enzyme surface.

Ammonia↗
PubMed2004

ULTRAMINE: a high-capacity polyethylene-imine-based polymer and its application as a scavenger resin.

The synthesis of a novel high-loading polyethylene-imine resin (ULTRAMINE) is described, and its application as a scavenger resin in various acylation reactions is demonstrated. The inverse suspension polymerization technique was used for the synthesis of well-defined spherical polymer beads. Polymer beads with different cross-linking densities were synthesized according to the degree of acryloylation of the polyethylene-imine polymer. The resin was characterized by various spectroscopic techniques. The size, shape, and morphological features of the resin were demonstrated by microscopy. The resin showed excellent swelling properties in both polar and nonpolar solvents. The chemical stability of the resin in various reagents and solvents was investigated and monitored by IR spectroscopy. The mechanical stability of the beads was determined by a single-bead compressive experiment. The ULTRAMINE beads can be used as an excellent scavenger for excess acylating reagent, as demonstrated for a variety of reactions. ULTRAMINE-red resin was derived from ULTRAMINE through exhaustive reduction of the amide carbonyl groups to yield an all-amine resin.

Imines↗
PubMed1985

Attempts to use cyanide ion to trap imine intermediates in the microsomal N-dealkylation of propranolol: formation of alpha-aminonitriles as artifacts when using ether for extraction.

Cyanide anion was used to attempt to trap possible imine intermediates in the oxidative N-dealkylation of propranolol (1). Reaction of 3-(1-naphthoxy)-1-amino-2-propanol (desisopropylpropranolol, 2) with acetone provided this expected intermediate in an approximately 7:1 ratio of oxazolidine 6 to imine 5, as determined by 1H NMR. The mixture when treated with sodium cyanide gave the expected alpha-aminonitrile 7. Microsomal oxidation of propranolol in the presence of sodium cyanide gave two cyanide-containing adducts as shown by GC-MS (12a and 12b). Using specifically deuterated propranolols (8, 9, 10, and 11) as substrates showed both of these cyanide-containing adducts to have lost the N-isopropyl group. Compounds 12a and 12b were shown to be diastereomeric alpha-aminonitriles arising from the reaction of 2 with propionaldehyde, a contaminant from the ether used for extraction, and cyanide anion. Authentic 7, stable to derivatization and GC-MS conditions, rapidly decomposed under the conditions of the metabolic experiments.

Animals↗
PubMedDate not supplied

Primary aliphatic amine metabolism: the formation of a stable imine metabolite.

The possible role of hydroxylamine and imine intermediates in the metabolism of amphetamine and related primary amines is discussed. The inherent instability of imines, has hitherto precluded the recognition of these compounds as metabolites of primary amines. During studies on the metabolism of o-methylbenzhydrylamine using washed hepatic microsomes from a number of mammalian species, the formation of o-methylbenzophenoneimine as a metabolite was observed. This metabolite was identified by preparative thin layer chromatography followed by gas-chromatography combined with mass spectrometry.

Amphetamines↗
PubMedDate not supplied

In vitro microsomal metabolism of nuclear chloro substituted secondary amines and imines.

The metabolism of N-(4-chlorobenzyl)-4-chloroaniline (CBCA), N-(4-chlorobenzyl)-4-chlorobenzylamine (CBCBA), and N-(4-chlorobenzylidene)-4-chlorobenzylamine (CBDCBA) were studied in vitro using rat liver microsomal preparations. The secondary amines produced the corresponding N-oxidation products (hydroxylamines and nitrones) and dealkylation products (4-chlorobenzaldehyde and primary amines). Both secondary amines failed to produce the corresponding amides, whilst the parent imine was detected as a metabonate. CBDCBA, the intermediate imine of CBCBA metabolism, was also incubated under similar conditions. However, no oxaziridine was detected.

Amines↗
PubMed2006

Novel imine from Hemsleya macrocarpa var. clavata.

The new substance hemsleyin imine A (1) was isolated along with (2S,3S,4R,2'R)-2-(2'-hydroxytetracosanoyl-amino)-octadecan-1,3,4-triol (2), (2S,3 R,4E,8E)-1-O-beta-D-glucopyranosyl -3-hydroxy-2-(2'R-hydroxypalmitoylamino)-4,8-octadecadiene (3) from the rhizomes of Hemsleya macrocarpa var. clavata. Their chemical structures were established mainly by spectral analysis and chemical evidence. Compound 1 possesses the skeleton of an imine moiety, which is novel in natural products.

Cucurbitaceae↗
PubMed1990

Oxidant-induced changes in the cellular energy homeostasis. A study with 3,5-dimethyl N-acetyl-p-benzoquinone imine and isolated hepatocytes.

Exposure of isolated hepatocytes to 400 microM 3,5-dimethyl N-acetyl-p-benzoquinone imine (3,5-diMe NAPQI), rapidly induced the formation of plasma membrane blebs. More than 50% of the viable cells were affected after 1 min incubation with 3,5-diMe NAPQI. Rapid loss of mitochondrial ATP, and sequential increases in ADP and AMP accompanied hepatocyte blebbing. 3,5-diMe NAPQI also induced a pronounced elevation of mitochondrial NADP level, whereas the NAD concentration was unaffected. Similar alterations in the adenine and pyridine nucleotide pools were found to occur in the cytosol, although at slower rates. During the initial phase of ATP loss and NADP production, there was also a concomitant decrease in the oxygen uptake of the hepatocytes. The decreases in energy substrates occurred in parallel to an increased uptake of trypan blue into the cells. Treatment of the hepatocytes with dithiothreitol, following 4 min exposure of the cells to 3,5-diMe NAPQI, reversed the quinone imine-induced changes in nucleotide levels and reduced the cytotoxicity. It is concluded that alteration of mitochondrial function, which results in changes in the cellular energy homeostasis, is an important event in the development of cytotoxicity caused by 3,5-diMe NAPQI.

Adenosine Triphosphate↗
PubMed1990

N-acetyl-p-benzoquinone imine-induced changes in the energy metabolism in hepatocytes.

The effect of N-acetyl-p-benzoquinone imine (NAPQI), a reactive metabolite of acetaminophen, on the energy metabolism in isolated hepatocytes was investigated. Incubation of cells with NAPQI (400 microM) resulted in an immediate uptake into the mitochondria, followed by both reduction and glutathione conjugation of the quinone imine. These reactions were extremely rapid and were associated with depletion of the mitochondrial ATP content (greater than 80% depletion after 1 min exposure). The loss of ATP was accompanied by increases in ADP and AMP, as well as NADP. No effect on mitochondrial NAD was observed during this initial phase. Similar alterations were produced by NAPQI in the cytosolic compartment. Furthermore, incubation of hepatocytes with NAPQI inhibited oxygen consumption by nearly 90% within 10 s. In parallel to these biochemical changes, there was marked bleb formation on the surface of the hepatocytes, which was found to precede cell death (trypan blue uptake). In conclusion, our results demonstrate that during exposure of hepatocytes to NAPQI, dramatic changes in cellular energy metabolism occur. These biochemical alterations may be caused by a rapid decrease in mitochondrial function, and they may play an important role in the initiation of NAPQI-induced cytotoxicity.

Adenosine Diphosphate↗
PubMed1984

Formation of imine derivatives between biologically occurring amines and oxo-steroids.

Various biologically occurring amines have been shown to react with 3-oxo-17-oxo and 20-oxo-steroids during solvent evaporation at room temperature to form a complex pattern of products in each case. Using aliphatic monoamines it was shown that imine derivatives are first formed which rapidly rearrange into yet unidentified compounds. The extent of the overall transformation of the oxo-steroid varied with the amine investigated. Thus histamine gave rise to a 95% conversion of 17 beta-hydroxy-4-androsten-3-one (testosterone), whereas epinephrine caused 5% transformation under the same conditions. Imine formation as an experimental error in studies on the biochemistry of steroids is suggested.

Amines↗
PubMed1994

Mutagenicity of K-region oxides and imines of chrysene, benzo[c]phenanthrene and benzo[g]chrysene in Salmonella typhimurium.

The K-region oxides and imines of chrysene, benzo[c]phenanthrene and benzo[g]chrysene were investigated for mutagenicity in Salmonella typhimurium TA98 and TA100, using two different exposure media. All six compounds were mutagenic under all four experimental conditions. The imines were 17-3800 times more potent than the corresponding oxides. Omission of KCl (125 mM) from the exposure medium resulted in enhanced mutagenic effects. The enhancement was stronger in strain TA98 (3.1-5.2-fold) than in strain TA100 (1.3-2.5-fold), suggesting an influence on the bacteria rather than on the chemicals.

Aziridines↗
PubMed2004

Design, synthesis, and evaluation of mixed imine-amine pyrrolobenzodiazepine dimers with efficient DNA binding affinity and potent cytotoxicity.

Synthesis of mixed imine-amine pyrrolobenzodiazepine (PBD) dimers that are comprised of DC-81 and secondary amine (N10) of DC-81 subunits tethered to their C8 positions through alkanedioxy linkers (comprised of three and five carbons) is described. These noncross-linking unsymmetrical molecules exhibit significant DNA minor groove binding ability and one of them 5b linked through the pentanedioxy chain exhibits efficient DNA binding ability (DeltaTm=11.0 degrees C) when compared to naturally occurring DC-81, 1 (DeltaTm=0.7 degrees C). The imine-amine PBD dimers exhibit promising in vitro antitumor activity in a number of human cancer cell lines.

Amines↗
PubMed2005

Microwave-assisted synthesis of imidazoles: reaction of p-toluenesulfonylmethyl isocyanide and polymer-bound imines.

A convenient method for the synthesis of 1,5-disubstituted imidazoles has been developed on a polymeric support using base-promoted 1,3-dipolar cycloaddition reaction of p-toluenesulfonylmethyl isocyanide (TOSMIC) with immobilized imines under microwave irradiation. The immobilized imines were synthesized by the reaction of various primary benzyl amines with 4-formyl-3-methoxyphenoxymethyl polystyrene in the presence of trimethyl orthoformate at room temperature. Cleavage from the polymeric support using trifluoroacetic acid gave the desired 1,5-disubstituted imidazoles with excellent yield and high purity.

Cyclization↗
PubMed2005

Background defining during the imine formation reaction in FT-IR liquid cell.

Imine formation is a very important chemical reaction because of its relevance to biological process. Therefore, it is crucial to follow whole reaction process in detail. The current work performed to monitor the whole imination reaction in real time in liquid cell by FT-IR spectroscopy. The complex spectral futures due to solvent, unreacted reagents, acid catalysis and other additives are eliminated by defining a background at the beginning or at any time during the reaction. This procedure also makes it possible to monitor the changes in the concentration of each component in the liquid cell. The consumption of the functional groups of the reagents results in absorbance due to the direct difference spectra while the appearance of functional groups is monitored as percentage transmittance. The concentration changes in the cell arising from the reaction gives the product spectra without having to isolate it from the mixture. It is also possible to see the intermediates appearing and disappearing during the reaction. This report also illustrates a brief application of the technique by time dependence of the peak highs in absorption (ABS) mode.

Calcium Fluoride↗
PubMed1999

Protein and nonprotein cysteinyl thiol modification by N-acetyl-p-benzoquinone imine via a novel ipso adduct.

N-acetyl-p-benzoquinone imine (NAPQI), a reactive metabolite of acetaminophen (APAP), can arylate and oxidize protein and nonprotein thiols in the pathogenesis of APAP-induced hepatotoxicity. We report the first direct evidence for the formation of a labile ipso adduct between glutathione (GSH) and NAPQI using a combination of techniques including liquid chromatography/tandem mass spectrometry and liquid chromatography/NMR spectroscopy. Decomposition kinetics of the GSH-NAPQI ipso adduct and product ratios suggested that the ipso adduct was readily reversible back to NAPQI under neutral and basic conditions. The significance of the ipso adduct is that it may migrate from its site of formation to other cell compartments where it can either oxidize protein thiols or covalently modify them. Ipso adduct formation with protein thiols was demonstrated with a cysteine protease, papain, whose catalytic activity relies on the presence of an active site cysteinyl thiol. The formation and reactions of cysteinyl thiol ipso adducts of NAPQI provides significant new insights into possible reactions of quinone imines with cellular peptides and proteins.

Acetaminophen↗
PubMed2005

Characterization of a 1:1 Cu-O2 adduct supported by an anilido imine ligand.

Copper(I) complexes of sterically hindered anilido imine ligands o-C6H4{N(C6H3(i)Pr2)}{C(R)=NC6H3(i)Pr2}- (L(1), R = H; L(2), R = CH3) have been prepared and characterized by spectroscopic and X-ray crystallographic methods. These complexes are highly reactive with O2, and in the case of L2 the product of low-temperature oxygenation was fully characterized by spectroscopic, X-ray crystallographic, and computational methods. The resonance Raman spectrum features an isotope-sensitive vibration at 974 cm(-1) (Delta(18O) = 66 cm(-1)), consistent with assignment as an O-O stretch. Despite the asymmetric coordination environment provided by the supporting anilido imine ligand, the X-ray crystal structure confirms rather symmetric side-on binding of the O2 moiety to the copper center, and the O-O bond length of 1.392(2) Angstroms indicates that this intermediate has significant Cu(III)-peroxo character. Theoretical calculations support this interpretation and predict that while a fully optimized end-on singlet geometry can be obtained, it is higher in energy than the side-on isomer by 3.5 kcal mol(-1) at the CASPT2/TZP level.

Anilides↗