- Picolinate-containing macrocyclic Mn2+ complexes as potential MRI contrast agents
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We report the synthesis of the ligand Hnompa (6-((1,4,7-triazacyclononan-1- yl)methyl)picolinic acid) and a detailed characterization of the Mn2+ complexes formed by this ligand and the related ligands Hdompa (6-((1,4,7,10-tetraazacyclododecan-1-yl)methyl)picolinic acid) and Htempa (6-((1,4,8,11-tetraazacyclotetradecan-1-yl)methyl)picolinic acid). These ligands form thermodynamically stable complexes in aqueous solution with stability constants of logKMnL = 10.28(1) (nompa), 14.48(1) (dompa), and 12.53(1) (tempa). A detailed study of the dissociation kinetics of these Mn 2+ complexes indicates that the decomplexation reaction at about neutral pH occurs mainly following a spontaneous dissociation mechanism. The X-ray structure of [Mn2(nompa)2(H2O) 2](ClO4)2 shows that the Mn2+ ion is seven-coordinate in the solid state, being directly bound to five donor atoms of the ligand, the oxygen atom of a coordinated water molecule and an oxygen atom of a neighboring nompa- ligand acting as a bridging bidentate carboxylate group (μ-η1-carboxylate). Nuclear magnetic relaxation dispersion (1H NMRD) profiles and 17O NMR chemical shifts and transverse relaxation rates of aqueous solutions of [Mn(nompa)]+ indicate that the Mn2+ ion is six-coordinate in solution by the pentadentate ligand and one inner-sphere water molecule. The analysis of the 1H NMRD and 17O NMR data provides a very high water exchange rate of the inner-sphere water molecule (kex 298 = 2.8 × 109 s-1) and an unusually high value of the 17O hyperfine coupling constant of the coordinated water molecule (AO/h = 73.3 ± 0.6 rad s-1). DFT calculations performed on the [Mn(nompa)(H2O)]+· 2H2O system (TPSSh model) provide a AO/h value in excellent agreement with the one obtained experimentally.
- Molnar, Eniko,Camus, Nathalie,Patinec, Veronique,Rolla, Gabriele A.,Botta, Mauro,Tircso, Gyula,Kalman, Ferenc K.,Fodor, Tamas,Tripier, Raphael,Platas-Iglesias, Carlos
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Read Online
- An octadentate bis(semicarbazone) macrocycle: A potential chelator for lead and bismuth radiopharmaceuticals
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A variant of 1,4,7,10-tetraazacyclododecane (cyclen) bearing two semicarbazone pendant groups has been prepared. The octadentate ligand forms complexes with Bi3+ and Pb2+. X-ray crystallography showed that the neutral ligand provides an eight-coordinate environment for both metal ions and intermolecular hydrogen bond interactions have influenced the coordination environments of both complexes in the solid state. NMR spectroscopy revealed a fluxional environment for both complexes. The ligand was radiolabeled with the α-emitting radioactive isotope 213Bi3+, which is used in systemic targeted radiotherapy. The resulting complex was stable in serum for at least 90 min (two decay half-lives). The Pb2+ complex has reasonably fast kinetics of formation (t1/2 = 20 min) at 25 °C and pH 7.4. The Bi3+ and Pb2+ complexes show kinetic stability in 1.2 M HCl (half-lives of 214 min and 47 min, respectively). This is the first description of a macrocycle bearing semicarbazone pendant groups and its utility in coordinating main group metals, specifically those with radiotherapeutic potential.
- Blower, Philip J.,Bruchertseifer, Frank,Davey, Patrick R. W. J.,Lange, Jaclyn L.,Ma, Michelle T.,Morgenstern, Alfred,Paterson, Brett M.,White, Jonathan M.
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Read Online
- TETRACYCLIC TETRAAMINES BY GLYOXAL-MACROCYCLIC TETRAAMINE CONDENSATION
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A series of new tetracyclic tetraamines have been synthesized in good to moderate yield by glyoxal-macrocyclic tetraamine condensation.
- Weisman, Gary R.,Ho, Suzzy C. H.,Johnson, Van
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Read Online
- A tris-macrocycle with proton sponge characteristics as efficient receptor for inorganic phosphate and nucleotide anions
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Synthesis, characterisation and proton-sponge behaviour of a new linear constrained tris-macrocycle (L), containing three cyclen (cyclen = 1,4,7,10-tetraazacyclododecane) reinforced macrocycles connected by two 2,6-pyridinediylbis(methyl-ene) linkers, is reported. Protonated forms of L are efficient receptors for inorganic phosphate and nucleotide anions (ATP and ADP). The binding properties of L toward these substrates have been investigated in aqueous solution by means of Potentiometrie titrations, determining the stability constants of the adducts. The interaction mode was clarified by using 1H and 31P NMR measurements in aqueous solution and by means of molecular modelling calculations carried out on differently protonated species of L as well as on sev-eral nucleotide-receptor adducts. The stability of the adducts is mainly due to charge-charge and hydrogen bonding inter-actions between the polyphosphate chain of nucleotides and the ammonium groups of L.
- Andrea Bencini,Biagini, Silvia,Giorgi, Claudia,Handell, Henri,Michel Le Baccon,Mariani, Palma,Paoletti, Piero,Paoli, Paola,Rossi, Patrizia,Tripier, Raphael,Valtancoli, Barbara
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Read Online
- Trans-Methylpyridine cyclen versus cross-bridged trans-methylpyridine cyclen. Synthesis, acid-base and metal complexation studies (metal = Co 2+, Cu2+, and Zn2+)
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The synthesis of the cross-bridged cyclen CRpy2 {4,10-bis((pyridin-2-yl)methyl)-1,4,7,10-tetraazabicyclo[5.5.2]tetradecane}, a constrained analogue of the previously described trans-methylpyridine cyclen Cpy2 is reported. The additional ethylene bridge confers to CRpy 2 proton-sponge type behaviour which was explored by NMR and potentiometric studies. Transition metal complexes have been synthesized (by complexation of both ligands with Co2+, Cu2+ and Zn 2+) and characterized in solution and in the solid state. The single crystal X-ray structures of [CoCpy2]2+, [CuCpy 2]2+ and [ZnCpy2]2+ complexes were determined. Stability constants of the complexes, including those of the cross-bridged derivative, were determined using potentiometric titration data and the kinetic inertness of the [CuCRpy2]2+ complex in an acidic medium (half-life values) was evaluated by spectrophotometry. The pre-organized structure of the cross-bridged ligand imposes an additional strain for the complexation leading to complexes with smaller thermodynamic stability in comparison with the related non-bridged ligand. The electrochemical study involving cyclic voltammetry underlines the importance of the ethylene cross-bridge on the redox properties of the transition metal complexes.
- Bernier, Nicolas,Costa, Judite,Delgado, Rita,Felix, Vitor,Royal, Guy,Tripier, Raphael
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- Preparation method of cyclen and intermediate thereof
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The invention discloses a preparation method of cyclen and an intermediate thereof, specifically a preparation method of a compound as shown in a formula 4. The method comprises the following step: in water, carrying out a reduction reaction as shown in the specification on a compound as shown in a formula 3 and hydrazine hydrate, wherein X is phosphoric acid or sulfuric acid, when X is phosphoric acid, n is 4/3, and when X is sulfuric acid, n is 2. The preparation method has the advantages of low cost, simple operation, easy purification of intermediates and products, high yield and purity, and suitableness for industrial production.
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Paragraph 0100-0102; 0127-0130
(2021/07/08)
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- Definition of the Labile Capping Bond Effect in Lanthanide Complexes
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Two macrocyclic ligands containing a cyclen unit, a methyl group, a picolinate arm, and two acetate pendant arms attached to two nitrogen atoms of the macrocycle either in trans (1,7-H3Medo2 ampa = 2,2′-(7-((6-carboxypyridin-2-yl)methyl)-10-met
- Rodríguez-Rodríguez, Aurora,Regueiro-Figueroa, Martín,Esteban-Gómez, David,Rodríguez-Blas, Teresa,Patinec, Véronique,Tripier, Rapha?l,Tircsó, Gyula,Carniato, Fabio,Botta, Mauro,Platas-Iglesias, Carlos
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supporting information
p. 1110 - 1117
(2017/02/05)
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- BIFUNCTIONAL do2pa DERIVATIVES, CHELATES WITH METALLIC CATIONS AND USE THEREOF
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The present invention relates to chelates resulting from the complexation of bifunctional do2pa derivatives ligands of formula (I), wherein the substituents R1, R1', R2, R2', R3, R3', Lsup
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Page/Page column 42
(2016/06/28)
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- Incorporation of Cobalt-Cyclen Complexes into Templated Nanogels Results in Enhanced Activity
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Recent advances in nanomaterials have identified nanogels as an excellent matrix for novel biomimetic catalysts using the molecular imprinting approach. Polymerisable Co-cyclen complexes with phosphonate and carbonate templates have been prepared, fully characterised and used to obtain nanogels that show high activity and turnover with low catalytic load, compared to the free complex, in the hydrolysis of 4-nitrophenyl phosphate, a nerve agent simulant. This work demonstrates that the chemical structure of the template has an impact on the coordination geometry and oxidation state of the metal centre in the polymerisable complex resulting in very significant changes in the catalytic properties of the polymeric matrix. Both pseudo-octahedral cobalt(III) and trigonal-bipyramidal cobalt(II) structures have been used for the synthesis of imprinted nanogels, and the catalytic data demonstrate that: i) the imprinted nanogels can be used in 15 % load and show turnover; ii) the structural differences in the polymeric matrices resulting from the imprinting approach with different templates are responsible for the molecular recognition capabilities and the catalytic activity. Nanogel P1, imprinted with the carbonate template, shows >50 % higher catalytic activity than P2 imprinted with the phosphonate.
- Jorge, Ana Rita,Chernobryva, Mariya,Rigby, Stephen E.J.,Watkinson, Michael,Resmini, Marina
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p. 3764 - 3774
(2016/03/08)
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- A high-purity torus cane rather method for the preparation of
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The invention provides a preparation method of high-purity cyclen. The method comprises the following preparation paths. Cyclen obtained by the method of the invention has high purity. At the same time, the method greatly reduces the energy consumption and the power cost, and thereby reducing the raw material cost; the method greatly improves the reaction rate, reduces the catalyst amount and the reaction temperature, thereby shortening the consuming time of the process, and reducing the process cost; and the method greatly reduces the acid amount consumption, and thereby greatly reducing the equipment loss. The preparation method improves the production efficiency, and enables the product quality to reach more than 99.8%; hydrazine hydrate is used for replacing diethylenetriamine for a hydrolysis reaction, so the process is suitable for industrialized production. The method of the invention is environmentally friendly, is cost-saving, and is suitable for environment-friendly industrialization.
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Paragraph 0051-0063; 0087; 0090-0091
(2017/03/21)
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- Copper(II) and gallium(III) complexes of trans -Bis(2-hydroxybenzyl) cyclen derivatives: Absence of a cross-bridge proves surprisingly more favorable
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Two cyclen (1,4,7,10-tetraazacyclododecane) derivatives bearing trans-bis(2-hydroxybenzyl) arms, the 1,7-(2-hydroxybenzyl)-1,4,7,10- tetraazacyclododecane (H2do2ph) and its cross-bridged counterpart (H2cb-do2ph), have been synthesized, aiming toward the possible use of their copper(II) and gallium(III) complexes in nuclear medicine. The protonation of both compounds was studied in aqueous solution as well as their complexes with Cu2+ and Ga3+ cations. The complexes of both ligands with Ca2+ and Zn2+ metal ions were also studied due to the abundance of these cations in biological media. In mild conditions the complexes of Ca2+ and Ga3+ with H 2cb-do2ph did not form. The behavior of the two ligands and their complexes was compared by the values of the equilibrium constants, the data of varied spectroscopic techniques, the values of redox potentials of their copper(II) complexes, and the resistance of the complexes to acid dissociation. It was expected that, as found for related pairs of cyclen and cyclam (1,4,8,11-tetraazacyclotetradecane) derivatives, the cross-bridged macrocyclic derivative could be an excellent ligand for the complexation of copper(II). Additionally, the N-2-hydroxybenzyl groups were chosen due to their known ability to coordinate the gallium(III) cation. Due to the small size of the latter cation and its particular propensity to form hexacoordinate complexes, it was also expected that there would be a good ability of both ligands for the uptake of Ga3+. Surprisingly, the results revealed that the cyclen derivative H2do2ph is the best ligand for the coordination of Cu 2+ and Ga3+ cations, not only from their thermodynamic stability as expected but also from their kinetic inertness, when compared with its cross-bridged counterpart.
- Esteves, Catarina V.,Madureira, Joana,Lima, Luis M. P.,Mateus, Pedro,Bento, Isabel,Delgado, Rita
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p. 4371 - 4386
(2014/05/20)
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- A novel synthesis of 1,4,7,10-tetraazacyclododecane by the tandem reaction of a vinylsulfonium salt
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1,4,7,10-Tetraazacyclododecane was synthesized through 4 steps by using easily available diphenylsulfonium triflate as a key annulation reagent. The reaction condition was very mild and the yield was high. After oxidation and hydrolysis, 1,4,7,10-Tetraazacyclododecane, which had been proven to be the pivotal precursor for a wide range of MRI contrast reagents, was produced in an overall yield of 31%.
- Huang, Rui,Xie, Chunsong,Huang, Lin,Liu, Jinhua
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p. 195 - 198
(2013/07/26)
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- Heteroditopic receptor based on crown ether and cyclen units for the recognition of zwitterionic amino acids
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The molecular recognition of five targeted amino acids differing in the nature of the side (R)- group and in the size of the aliphatic chain, glycine (Hgly), phenylalanine (Hphe), glutamic acid (Hglu-), 4-aminobutyric acid (Hgaba), and 6-aminohexanoic acid (Heahx), has been studied with a new heteroditopic receptor based in two distinct macrocycles, a cyclen and a crown ether moiety. The bismacrocycle L was synthesized via the bis-aminal route allowing to obtain the designed compound in gram scale and in good yield. Protonation constants of L and its binding constants with amino acids were determined by potentiometry in H2O/MeOH (1:1 v/v) solutions at 298.2 K and I=0.10 mol dm-3 in NMe4NO3. Stronger binding ability of the HnLn+ receptor for α-amino acids, Hgly and Hphen, than for the other studied substrates were found. Structural data derived from NMR studies showed that the binding of α-amino acids result from the cooperative participation of hydrogen bonds between the carboxylate group of amino acids and the polyammonium sites of cyclen, and the ion-dipole interactions between the ammonium group of the amino acids and the oxygen atoms of the crown ether.
- Bernier, Nicolas,Esteves, Catarina V.,Delgado, Rita
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scheme or table
p. 4860 - 4868
(2012/08/28)
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- Monopicolinate cyclen and cyclam derivatives for stable copper(II) complexation
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The syntheses of a new 1,4,7,10-tetraazacyclododecane (cyclen) derivative bearing a picolinate pendant arm (HL1), and its 1,4,8,11- tetraazacyclotetradecane (cyclam) analogue HL2, were achieved by using two different selective-protection methods involving the preparation of cyclen-bisaminal or phosphoryl cyclam derivatives. The acid-base properties of both compounds were investigated as well as their coordination chemistry, especially with Cu2+, in aqueous solution and in solid state. The copper(II) complexes were synthesized, and the single crystal X-ray diffraction structures of compounds of formula [Cu(HL)](ClO4)2· H2O (L = L1 or L2), [CuL1](ClO4) and [CuL2] Cl·2H2O, were determined. These studies revealed that protonation of the complexes occurs on the carboxylate group of the picolinate moiety. Stability constants of the complexes were determined at 25.0 °C and ionic strength 0.10 M in KNO3 using potentiometric titrations. Both ligands form complexes with Cu2+ that are thermodynamically very stable. Additionally, both HL1 and HL2 exhibit an important selectivity for Cu2+ over Zn2+. The kinetic inertness in acidic medium of both complexes of Cu2+ was evaluated by spectrophotometry revealing that [CuL2]+ is much more inert than [CuL1]+. The determined half-life values also demonstrate the very high kinetic inertness of [CuL2]+ when compared to a list of copper(II) complexes of other macrocyclic ligands. The coordination geometry of the copper center in the complexes was established in aqueous solution from UV-visible and electron paramagnetic resonance (EPR) spectroscopy, showing that the solution structures of both complexes are in excellent agreement with those of crystallographic data. Cyclic voltammetry experiments point to a good stability of the complexes with respect to metal ion dissociation upon reduction of the metal ion to Cu+ at about neutral pH. Our results revealed that the cyclam-based ligand HL2 is a very attractive receptor for copper(II), presenting a fast complexation process, a high kinetic inertness, and important thermodynamic and electrochemical stability.
- Lima, Luis M. P.,Esteban-Gomez, David,Delgado, Rita,Platas-Iglesias, Carlos,Tripier, Raphael
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scheme or table
p. 6916 - 6927
(2012/08/28)
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- From flexible to constrained tris(tetraamine) ligands: Synthesis, acid-base properties, and structural effect on the coordination process with nucleotides
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This work presents the synthesis and characterization of L2 and L3, which formed with the previously described ligand L1 a family of three tris(tetraamine) ligands based on a mesitylenyl spacer, The trimeric ligands differ from one to the other by the nat
- Delepine, Anne-Sophie,Tripier, Raphael,Le Baccon, Michel,Handel, Henri
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scheme or table
p. 5380 - 5390
(2010/11/18)
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- Synthesis and NMR characterization of cis and trans decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene. Solid state structure of the trans stereoisomer. Modelling studies
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The reduction with Vitride of the cis and trans isomers of octahydro-2a,4a,6a,8a-tetraazacyclopenten[fg]acenaphthylene 1,2-diones (5 and 6) and octahydro-2a,4a,6a,8a-tetraazacyclopenten[fg]acenaphthylene 3,4-diones (7 and 8) led to the cis 9 and the so far unknown trans 10 isomers of decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene. The stereochemistry of 9 and 10 was determined by comparison of the NMR coupling constants of the proton signals of the ethinic bridge. The results were confirmed by the solid state structure of the trans isomer (10) determined by single crystal X-ray diffraction. Given that the trans bis-aminal species 2 and 4 can undergo rearrangement, i.e. stereoisomerization into the corresponding cis ones (1 and 3, respectively), the conformational behaviour of species 1-4 was investigated by means of both molecular mechanics (MM) and quantum chemical (QC) approaches. The theoretical study was completed by including diamides 5-8 and the final products 9 and 10.
- Argese, Maria,Brocchetta, Marino,De Miranda, Mario,Ferraris, Andrea,Dapporto, Paolo,Paoli, Paola,Rossi, Patrizia
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p. 6915 - 6923
(2008/02/11)
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- Method of preparing cis-8b-methyldecahydro-2a,4a,6a,8a-tetraazacyclopenta[fg] acenaphthylene, cis-decahydro-2a,4a,6a,8a-tetraazacyclopenta[fg] acenaphthylene, cyclene and functionalised cyclenes
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A method of preparing cyclene having formula (I) from triethylenetetraamine having formula (VIII) or ethylenediamine having formula (VIII′) includes a series of steps. The first series of steps (I) includes a step A (one-pot preparation of the compound having formula (IIa) from the compound having formula (VIII)), followed by a step B (transforming the compound having formula (IIa) into cyclene having formula (I)). The second series of steps (II) includes a step C (preparing the compound having formula (IIb) from the compound having formula (VIII)), followed by a step D (transforming the compound having formula (IIb) into cylcene having formula (I)). The third series of steps (III) includes a step E involving the one-pot preparation of the compound having formula (IIa) from the compound having formula (VIII), followed by a step B involving the transformation of the compound having formula (IIa) into cyclene having formula (I).
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(2010/11/23)
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- Complexes of cyclic polyaza chelators with cations of alkaline earth metals for enhanced biological activity
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Cyclic polyaza chelators that possess high affinity and specificity for first transition series metal cations exhibit an unanticipated improvement in biological activity when administered as complexes with cations of the alkaline earth metals, Ca(II) and Mg(II), most notably Ca(II). By virtue of this improvement, these complexes are particularly effective in the treatment of pathological conditions, including ischemia and ischemia-reperfusion injury.
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(2010/02/11)
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- Process for the preparation of decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene and functionalized derivatives
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A process for the preparation of compound of formula (I A), decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]accnaphthylene and the corresponding functionalized compounds of general formula (1), intermediates for the preparation of 1,4,7,10-tetraazacyclododecane (II A) and corresponding derivatives (II), by preparation of compounds of general formula (III) and subsequent reduction thereof.
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- A PROCESS FOR THE PREPARATION OF TETRAAZAMACROCYCLES
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A process for the preparation of tetraazamacrocycles of general formula (I) wherein n, p and q can independently be 0 or 1, comprising the following steps: a): condensation of polyamines with a glyoxal derivative; b): condensation of the resulting compound with an alkylating agent; c): oxidation of the resulting compound with an oxidizing agent, to give a mixture of oxidated products which is submitted to d): hydrolysis in acid aqueous solution, to give the compound of formula (I).
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- 1,4,7,10-tetraazacyclododecane-1,4-diacetic acid derivatives as chelating agents
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Compounds of formula (I) in which R is in which R is hydrogen, a straight or branched or cyclic C1-C6alkyl group, unsubstituted or substituted by 1 to 10 oxygen atoms, or a C1-C20alkyl group, optionally interrupted by a phenylene, in turn substituted by a straight or branched C1-C6alkyl group, unsubstituted or substituted by 1 to 3 C1-C7alkyl groups; the phenylene group being unsubstituted or substituted by alkoxy, carboxy, sulfamoyl, hydroxyalkyl, amino groups; as well as its complexes with a bi- or trivalent metal ion having an atomic number from 20 to 31, 39, 42, 43, 44, 49, or from 57 to 83, as well as its salts with anions of physiologically acceptable organic acids chelated complexes of these compounds are used as contrast agents for nuclear magnetic resonance imaging.
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- A new, facile synthesis of 1,4,7,10-tetraazacyclododecane: Cyclen
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This report outlines a new and efficient synthesis of cyclen (1,4,7,10-tetraazacyclododecane, 1) utilizing bis-imidazoline, 6 (1,1′-ethylenedi-2-imidazoline), with 1,2-dibromoethane. General conditions were developed, allowing for the simple, three-step synthesis of 1 at the multigram scale with an isolated overall yield approaching 65%. The cyclization of 6 produced by the condensation of triethylene tetraamine (TETA) with N,N-dimethylformamide dimethyl acetal, gave the twelve membered, imidazolinium, cyclized intermediate bromide salt, 7 (2,3,4,5,6,7,8,8c-octahydro-1H 4a,6a,8a-triaza-2a-azoniacyclopent[fg]acenaphthylene), which hydrolyzed to 1 with the use of hot, aqueous caustic. Hydrolysis of 7 under milder conditions formed the 1,4,7,10-tetraazabicyclo[8.2.1]-tridecan-13-one (20). Mechanistically, the formation of 7 may be rationalized as involving a diaminocarbene that undergoes an intramolecular carbon-hydrogen insertion.
- Athey, Phillip S.,Kiefer, Garry E.
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p. 4081 - 4085
(2007/10/03)
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- Bis-aminals: Efficient tools for bis-macrocycle synthesis
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Tetraazamacrocyclic bis-aminals prove to be excellent tools for the synthesis of symmetrical, dissymmetrical or functionalized bis-tetraazamacrocycles. The key feature of the process is the separation of insoluble mono- or bis-quaternary ammonium salts from solution during the course of the alkylation reaction.
- Le Baccon,Chuburu,Toupet,Handel,Soibinet,Dechamps-Olivier,Barbier,Aplincourt
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p. 1168 - 1174
(2007/10/03)
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- Process for the preparation of tetraazamacrocycles
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PCT No. PCT/EP98/01882 Sec. 371 Date Aug. 11, 1999 Sec. 102(e) Date Aug. 11, 1999 PCT Filed Apr. 1, 1998 PCT Pub. No. WO98/45296 PCT Pub. Date Oct. 15, 1998Procedures for preparing compounds of formula (I) in which n, p and q or independently 0 or 1, are prepared according to the reaction scheme:
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- Process for the preparation of tetraazamacrocycles
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A process for the preparation of tetraazamacrocycles of general formula (I) STR1 wherein n, p and q can independently be 0 or 1, comprising the following steps: a): condensation of polyamines with a glyoxal derivative; b): condensation of the resulting compound with an alkylating agent; c): oxidation of the resulting compound with an oxidizing agent, to give a mixture of oxidated products which is submitted to d): hydrolysis in acid aqueous solution, to give the compound of formula (I).
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- Condensation of glyoxal with triethylenetetraamine. Stereochemistry, cyclization and deprotection
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A mixture of bis-aminal isomers was obtained from aqueous glyoxal- triethylenetetraamine condensation. The irreversible isomerization of the species was observed and a new synthesis of cyclen proposed.
- Herve, Gwenaelle,Bernard, Helene,Bris, Nathalie Le,Baccon, Michel Le,Yaouanc, Jean-Jacques,Handel, Henri
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p. 2517 - 2520
(2007/10/03)
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- Synthesis and transition-metal complexes of new cross-bridged tetraamine ligands
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New cross-bridged tetraamine ligands (bicyclo[6.6.2], [6.5.2] and [5.5.2] systems) are synthesized; complexation of CuII and NiII demonstrates that the ligands coordinate selected metals in a cleft.
- Weisman, Gary R.,Wong, Edward H.,Hill, Daniel C.,Rogers, Mark E.,Reed, David P.,Calabrese, Joseph C.
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p. 947 - 948
(2007/10/03)
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