New Acyclic Dimers of Cholic Acid with Oxamide and Hydrazide Spacers

Summary. Three new acyclic dimers of cholic acid with oxamide and isomeric hydrazide (N,N′-diacylhydrazine) spacers were obtained. The oxamide spacers bind two identical steroidal subunits through position 3 (head-to-head dimer) or position 23 (tail-to-tail dimer). In the case of a third dimer the hydrazine moiety binds two molecules of cholic acid through position 24 (tail-to-tail dimer).     

Dimeric Cholaphanes with Oxamide Spacers

Summary. Two new dimeric cholaphanes with oxamide spacers were prepared. The spacers bind two identical steroidal subunits through positions 3,3′ and 24,24′ (head-to-head dimer) or positions 3,24′ and 3′,24 (head-to-tail dimer).     

Dimeric Cholaphanes with Oxamide Spacers

Two new dimeric cholaphanes with oxamide spacers were prepared. The spacers bind two identical steroidal subunits through positions 3,3′ and 24,24′ (head-to-head dimer) or positions 3,24′ and 3′,24 (head-to-tail dimer).     

Synthesis and Antagonistic Activity of Two Covalently Linked Dimers of Adrenocorticotropin-(11-24)-tetradecapeptide

The chemical synthesis of two dimers of the sequence 11 to 24 of adrenocorticotropin is described. The two monomers were covalently linked through their N-or C-termini, respectively, using N-acetylglutamic acid or lysine amide as spacers. Compared to the monomer, the first dimer showed moderately, the second strongly increased inhibitory potency upon steroidogenesis in isolated adrenal cells.     

In vitro antibacterial and antifungal assay of poly‐(ethylene oxamide‐N,N′‐diacetate) and its polymer–metal complexes

A new polyester, poly‐(ethylene oxamide‐N,N′‐diacetate) (PEODA), containing glycine moiety was synthesized by the reaction of oxamide‐N,N′‐diacetic acid and ethylene glycol and its polymer–metal complexes were synthesized with transition metal ions. The monomer oxamide‐N,N′‐diacetic acid was prepared by the reaction of glycine and diethyl oxalate. The polymer and its metal complexes were characterized by elemental analysis and other spectroscopic techniques. The in vitro antibacterial activities of all the synthesized polymers were investigated against some bacteria and fungi. The analytical data revealed that the coordination polymers of Mn(II), Co(II) and Ni(II) are coordinated with two water molecules, which are further supported by FTIR spectra and TGA data. The polymer–metal complexes showed excellent antibacterial activities against both types of microorganisms; the polymeric ligand was also found to be effective but less so than the polymer–metal complexes. On the basis of the antimicrobial behavior, these polymers may be used as antifungal and antifouling coating materials in fields like life‐saving medical devices and the bottoms of ships. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and characterization of a cadmium(II)–organic supramolecular coordination compound based on the multifunctional 2‐amino‐5‐sulfobenzoic acid ligand

Much attention has been paid by chemists to the construction of supramolecular coordination compounds based on the multifunctional ligand 5‐sulfosalicylic acid (H₃SSA) due to the structural and biological interest of these compounds. However, no coordination compounds have been reported for the multifunctional amino‐substituted sulfobenzoate ligand 2‐amino‐5‐sulfobenzoic acid (H₂asba). We expected that H₂asba could be a suitable building block for the assembly of supramolecular networks due to its interesting structural characteristics. The reaction of cadmium(II) nitrate with H₂asba in the presence of the auxiliary flexible dipyridylamide ligand N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide (4bpme) under ambient conditions formed a new mixed‐ligand coordination compound, namely bis(3‐amino‐4‐carboxybenzenesulfonato‐κO¹)diaquabis{N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide‐κN}cadmium(II)–N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide–water (1/1/4), [Cd(C₇H₆NO₅S)₂(C₁₄H₁₄N₄O₂)₂(H₂O)₂]·C₁₄H₁₄N₄O₂·4H₂O, (1), which was characterized by single‐crystal and powder X‐ray diffraction analysis (PXRD), FT–IR spectroscopy, thermogravimetric analysis (TG), and UV–Vis and photoluminescence spectroscopic analyses in the solid state. The central Cd^II atom in (1) occupies a special position on a centre of inversion and exhibits a slightly distorted octahedral geometry, being coordinated by two N atoms from two monodentate 4bpme ligands, four O atoms from two monodentate 4‐amino‐3‐carboxybenzenesulfonate (Hasba⁻) ligands and two coordinated water molecules. Interestingly, complex (1) further extends into a threefold polycatenated 0D→2D (0D is zero‐dimensional and 2D is two‐dimensional) interpenetrated supramolecular two‐dimensional (4,4) layer through intermolecular hydrogen bonding. The interlayer hydrogen bonding further links adjacent threefold polycatenated two‐dimensional layers into a three‐dimensional network. The optical properties of complex (1) indicate that it may be used as a potential indirect band gap semiconductor material. Complex (1) exhibits an irreversible dehydration–rehydration behaviour. The fluorescence properties have also been investigated in the solid state at room temperature.     

Preparation and Acid‐Responsive Photophysical Properties of T‐Shaped π‐Conjugated Molecules Containing a Benzimidazole Junction

T‐shaped π‐conjugated molecules with an N‐methyl‐benzimidazole junction have been synthesized and their acid‐responsive photophysical properties owing to the change in the π‐conjugation system are discussed. T‐shaped π‐conjugated molecules consist of two orthogonal π‐conjugated systems including a phenyl thiophene extended from the 2‐position and alkyl phenylenes connected through various π‐spacers from the 4,7‐positions of the N‐methyl‐benzimidazole junction. The π‐spacers, such as thiophene, ethyne, and ethane, have an effect on the acid response of photophysical properties in terms of changes in conformation, excited‐state energy and charge‐transfer (CT) characteristics. In particular, the π‐conjugated molecule with ethynyl spacers exhibited a marked redshift in the fluorescence spectrum with a large Stokes shift upon the addition of acid, whereas the other molecules showed substantial quenching. The redshift in emission was studied in detail by temperature‐dependent fluorescence measurements, which indicated the transition to a CT state over the finite activation energy at the excited state. The change in the frontier molecular orbitals upon acid addition was further discussed by means of DFT calculations.     

Cationic oligomerization of bicyclic oxalactam

Cationic oligomerization of bicyclic oxalactam, 8-oxa-6-azabicyclo[3.2.1]octan-7-one [abbreviated as BOL ( 1 )], was carried out at 0–60°C with trifluoromethanesulfonic acid and borontrifluoride etherate as catalysts to obtain the oligomer mixture at high yield. From the structural analysis of the isolated dimer, a N-(2(e)-carbamoyltetrahydropyran-6(e)-yl)-8-oxa-6-azabicyclo[3.2.1]octan-7-one, the oligomerization proceeded through the ⁵C-⁶N scission in ( 1 ) but not through the ⁶N-⁷C (amide group) scission as generally observed in common lactams. This peculiar oligomerization must result from the protonation to the oxamide unit in the BOL molecule.     

Condensation of Trifluoromethanesulfonamide with Paraformaldehyde and Oxamide

Depending on the conditions, three-component condensation of trifluoromethanesulfonamide with paraformaldehyde and oxamide led to the formation of linear products, N-mono- and N,N’-bis[(trifluoromethylsulfonyl)aminomethyl]oxamide, bis[(trifluoromethylsulfonyl)aminomethyl] ethanedioate, as well as of hydrolysis and cyclization product, N-(4,5-dioxo-1,3-oxazolidin-3-ylmethyl)trifluoromethanesulfonamide.     

Dinuclear Tin(II) Complex of a Bulky cis‐Oxamide: Synthesis,Characterization, Crystal Structure,and DFT Studies

The reaction of the di‐lithiated oxamide of 1 with two equivalents of SnCl₂ provided the tin trans‐oxamide 3 . In solution, spectroscopic analysis suggests exclusively the formation of a trans‐oxamide (trans‐ 3 ). However, the solid state shows an atypical cis‐oxamide (cis‐ 3 ), where the oxamide fragment acts as an anti‐Janus head ligand. An ¹¹⁹Sn‐NMR variable temperature experiment ([D₈]THF) of the trans‐oxamide (trans‐ 3 ) was performed however, at lower temperature no additional signal was observed, which confirmed the absence of a dynamic equilibrium. Dispersion‐corrected density functional calculations revealed that the cis conformation of this tin(II) oxamide complex is more stable than the trans isomer by 1.4 kcal · mol^–1.     

Synthesis,structure, DNA-binding,and cytotoxic activities of N-(5-chloro-2-hydroxyphenyl)-N′-[3-(2-hydroxyethylamino)propyl]oxamide and its dicopper(II) complex

A dissymmetrical N,N′-bis(substituted)oxamide, N-(5-chloro-2-hydroxyphenyl)-N′[3-(2-hydroxyethylamino)propyl]oxamide (H₃oxpep), and its dicopper(II) complex, [Cu₂(oxpep)(phen)]ClO₄ (1) (phen?=?1,10-phenanthroline), were synthesized. The crystal structure of 1 was determined by single-crystal X-ray diffraction. In 1, Cu1 and Cu2 are bridged by cis-oxpep^3? with Cu?···?Cu separation of 5.2007(6)?Å. Cu1 is in a distorted square-pyramidal environment, while Cu2 has a square-planar coordination geometry. The 3-D supramolecular structure of 1 is formed through π–π stackings and hydrogen bonds. The DNA-binding properties and cytotoxic activities of the two compounds were investigated. The results suggest that the two compounds can interact with HS-DNA by intercalation with binding affinities following the order 1?>?H₃oxpep, which is consistent with their anticancer activities.     

Fluorescent Short-Stranded Helical Foldamers Based on L-shaped Dibenzopyrrolo[1,2-a][1,8]naphthyridine

Helical structures were constructed by using π-spacer-bridged dimers of dibenzopyrrolo[1,2-a][1,8]naphthyridine, which has a highly fluorescent L-shaped π-extended skeleton. Three dimers with biphenylene (dimer 1 ), phenanthrene (dimer 2 ), and m-phenylene (dimer 3 ) spacers, as well as a fixed-helical dimer 4 where two quinolone rings were covalently cross-linked, were designed and prepared. ¹H NMR and ROESY spectra revealed that dimers 1 and 2 adopted helical forms in solution, whereas dimer 3 did not. The helical conformation of 1 was strengthened by addition of either polar or nonpolar solvents to the chloroform solution, which suggested that π–π stacking was the main contributor to the stabilization of the helical structure. All of the dimers, including fixed-helical dimer 4 , emitted fluorescence with high quantum yields (ϕ=0.79–0.86).     

Creation of Ternary Multicomponent Crystals by Exploitation of Charge‐Transfer Interactions

Four new ternary crystalline molecular complexes have been synthesised from a common 3,5‐dinitrobenzoic acid (3,5‐dnda) and 4,4′‐bipyridine (bipy) pairing with a series of amino‐substituted aromatic compounds (4‐aminobenzoic acid (4‐aba), 4‐(N,N‐dimethylamino)benzoic acid (4‐dmaba), 4‐aminosalicylic acid (4‐asa) and sulfanilamide (saa)). The ternary crystals were created through the application of complementary charge transfer and hydrogen‐bonding interactions. For these systems a dimer was created through a charge‐transfer interaction between two of the components, while hydrogen bonding between the third molecule and this dimer completed the construction of the ternary co‐crystal. All resulting structures display the same acid ??? pyridine interaction between 3,5‐dnba and bipy. However, changing the third component causes the proton of this bond to shift from neutral OH ??? N to a salt form, O^? ??? HN⁺, as the nature of the group hydrogen bonding to the carboxylic acid was changed. This highlights the role of the crystal environment on the level of proton transfer and the utility of ternary systems for the study of this process.     

COORDINATION OF CU2± BY MONO-AMINOALKYLOXAMIDES IN AQUEOUS SOLUTION

Abstract

Complex formation equilibria of Cu^2± complexes of N-(2-aminoethyl)(oxamide, N-3-aminopropyl)oxamide, 1,8-diamino-3,6-diazaoctane-7,8-dione and 1,10-diamino-4,8-diazaoctane-9,10-dione in aqueous solution at 25°C ± 0.1°C and I = 0.1 mol dm^?3 (KNO₃) have been studied using potentiometric and spectrometric titrimetry. Mixed ligand titrations using 2,2′-bipyridyl as the second ligand have been added in order to obtain unambiguous results. The Cu^2± complexes of the monoalkyl substituted oxamides studied can be classified into three groups: (1) CuLH₁ and CuLH₂ complexes; these complexes have a single deprotonated oxamide group in a trans configuration; (2) a CuLH_?3 complex; this complex has a doubly deprotonated oxamide group in a cis configuration; (3) Cu₂LH_?2, Cu₃L₂H_?4 and Cu₃L₂H_?5 complexs; these polynuclear complexes have the doubly deprotonated oxamide group in a trans configuration. Deprotonation of the primary amide group in the Cu₂LH_?2 complex of these ligands occurs before pH = 5. This unprecedented deprotonation of a primary amide group under these conditions is due to the cooperation of both strong and optimally positioned coordinating groups. The concept of amide oxygen anchoring is introduced.     

Synthesis, characterization, and biological properties of N-phenolato-N′-(3-dimethylaminopropyl)oxamide and its binuclear copper(II) complexes

A new asymmetric N,N′-bis(substituent)oxamide ligand, N-phenolato-N′-(3-dimethylaminopropyl)oxamide (H₃pdmapo), and two of its binuclear Cu(II) complexes with different terminal ligands, namely [Cu₂(pdmapo)(phen)(H₂O)](ClO₄) (1) and [Cu₂(pdmapo)(bpy)(CH₃OH)](ClO₄) (2), where phen = 1,10-phenanthroline and bpy = 2,2′-bipyridine, have been synthesized and characterized. The crystal structures of both complexes have been determined by single-crystal X-ray diffraction. Both structures contain binuclear Cu(II) cationic complexes with pdmapo^3? ligands. The asymmetric pdmapo^3? ligands bridge two Cu(II) atoms in the cis conformation and the Cu···Cu separations through the oxamide bridge are 5.2046(18) and 5.207(2) Å for complexes 1 and 2, respectively. The coordination environments of the two Cu(II) atoms in each binuclear complex are different. The copper occupying the inner site of the pdmapo^3? ligand is four-coordinated in a CuN₃O distorted square-planar environment, while the other is five-coordinated in a square pyramid geometry. In complex 1, O–H···O and C–H···O hydrogen bonds link the complex into a one-dimensional chain. In complex 2, O–H···O hydrogen bonds link the molecules to form a dimer, together with two types of strong π–π interactions, giving a two-dimensional network structure. The cytotoxicities and DNA-binding properties of H₃pdmapo and the two complexes were studied. The experimental evidence suggests that the ligand binds to DNA via a groove binding mode, while the binuclear complexes bind intercalatively to DNA.     

1‐Methyl‐5,6,7,8‐tetra­hydro­quin­ox­alin‐2(1H)‐one

The title compound, C₉H₁₂N₂O, crystallizes in a triclinic unit cell, with two crystallographically independent mol­ecules in the asymmetric unit. The two independent mol­ecules adopt different modes of packing. One type of mol­ecule is arranged in infinite columns, while the other type packs as dimers, forming spacers between the parallel columns. Each type of mol­ecule is arranged in pairs related by inversion centers. The distances between potential reaction centers are 3.395 (2), 3.457 (2) and 3.522 (2) Å. As a result of the symmetry of the pairs and the close distances between the potential photoreactive centers, it is expected that the dimer will be the anti–trans isomer.     

Bildung oktaedrischer Komplexe durch cis-Addition an planar-quadratisches Bis(oxamidoximato)nickel(II): drei Strukturbeispiele

Formation of Octahedral Complexes via cis-Addition to Square Planar Bis (oxamideoximato)nickel(II): Three Structure Examples In the reaction of orange square planar bis(oxamide oximato)nickel(II) with acids, blue to blue-green octahedral complexes are formed with neutral oxamide oximide ligands and two acid anions in cis-positions. Three compounds are described: cis-dichlorobis(oxamide oxime)nickel(II) ( 1 ), NiCl₂(C₂H₆N₄O₂)₂, M_r = 365.81, monoclinic P2₁/n, a = 6.641(2), b = 14.086(4), c = 13.473(3) Å, β = 96.26(2)°, V = 1 252.8 ų, Z = 4, d_c = 1.94 gcm^?3, final R_w = 0.031 for 4090 reflections. In cis-di(sulfanilato)bis(oxamide oxime)nickel(II) dihydrate ( 2 ) one sulfanilic anion coordinates via the sulfonic acid group, the other one via the amino group; Ni(C₆H₆NO₃S)₂(C₂H₆N₄O₂)₂ · 2 H₂O, M_r = 675.30, monoclinic P2₁, a = 6.879(3), b = 14.305(5), c = 13.930(5) Å, β = 103.62(4)°, V = 1332 Å, Z = 2, d_c = 1.68 gcm^?3, R = 0.067 for 2693 reflections. In catena-μ-(phthalato)bis(oxamide oxime)nickel(II) tetrahydrate ( 3 ) bidentate bridging phthalate anions lead to chain formation; Ni(C₈H₄O₄)(C₂H₆N₄O₂)₂ · 4H₂O, M_r = 531.09, monoclinic P2₁/c, a = 10.633(8), b = 11.324(5), c = 17.680(14) Å, β = 98.25(7)°, V = 2107 ų, Z = 4, d_c = 1.67 gcm^?3. Final R = 0.110 for 3290 reflections.     

Hydrophilic polymethacrylates containing cholic acid‐ethylene glycol derivatives as pendant groups

In an effort to improve the hydrophilicity of bile acid containing polymers, we have synthesized new methacrylate monomers by incorporating ethylene glycol and oligo(ethylene glycol) spacers of different lengths between cholic acid and methacrylate residues. The monomers were subsequently polymerized by free radical reaction in solution. The methyl ester protecting groups on the cholic acid residue were selectively hydrolyzed to restore the carboxylic acid group of cholic acid. Water absorption tests showed that the hydrophilicity of the polymers was improved with increasing length of oligo(ethylene glycol) spacers and upon restoration of the carboxylic acid group of the cholic acid residue.     

草酰胺配体的微波合成

在微波辐照下, 分别由苯胺、取代苯胺和草酸通过无溶剂法反应, 合成出N,N′-二(苯基)草酸二酰胺和N,N′-二(取代苯基)草酸二酰胺, 利用¹H NMR, MS和元素分析对其结构进行了表征. 研究表明, 增加辐照功率选择合适的辐照时间有利于产物收率的提高, 甲基或氯单取代的苯胺得率高于苯胺, 增加固液两相的接触面积可大大提高产物的收率.     

Syntheses and crystal structure of binuclear μ-oxamido copper(II) complexes containing 1,4,7-triazacyclononane as a terminal ligand

Two new binuclear copper(II) complexes, Cu(tacn)Cu(oxpn)(ClO₄)₂·C₂H₅OH (1), and Cu(tacn)Cu(oxap)(ClO₄)₂·CH₃OH (2), have been prepared from the planar fragment Cu(oxpn) and Cu(oxap) (tacn denotes 1,4,7-triazacyclononane, oxpn and oxap stand for the dianions of N,N′-bis(3-aminopropyl)oxamide, and N,N′-bis(2-aminopropyl)oxamide, respectively). The complexes have been characterized by means of elemental analyses and IR, and UV spectra. The crystal structure of compound 1 shows that copper(II) coordinates to the four nitrogen atoms of oxpn in a square-planar environment and the other copper(II) ion is in a distorted square-pyramidal environment.