Synthesis of a zirconium sandwich complex and crystallographic characterization of its adduct with tetrahydrofuran

Reductive elimination of alkane from a silylated bis-indenyl zirconium isobutyl hydride affords a zirconium sandwich complex with an unusual eta6 indenyl ligand. Crystallographic characterization of its adduct with tetrahydrofuran has been achieved and reveals significant localization in the six-membered ring. Complexation of more potent ligands such as carbon monoxide and diphenylacetylene are effective in promoting haptotropic rearrangement of the eta6 indenyl ligand and provides familiar bent zirconocene derivatives. The zirconium sandwich compound also undergoes oxidative addition of carbon-hydrogen bonds of pyridyl ligands, resulting in a crystallographically characterized dimethylamino pyridyl hydride complex of zirconium.     

Structural and initial biological analysis of synthetic arylomycin A2

The growing threat of untreatable bacterial infections has refocused efforts to identify new antibiotics, especially those acting by novel mechanisms. While the inhibition of pathogen proteases has proven to be a successful strategy for drug development, such inhibitors are often limited by toxicity due to their promiscuous inhibition of homologous and mechanistically related human enzymes. Unlike many protease inhibitors, inhibitors of the essential type I bacterial signal peptidase (SPase) may be more specific and thus less toxic due to the enzyme's unique structure and catalytic mechanism. Recently, the arylomycins and related lipoglycopeptide natural products were isolated and shown to inhibit SPase. The core structure of the arylomycins and lipoglycopeptides consists of a biaryl-linked, N-methylated peptide macrocycle attached to a lipopeptide tail, and in the case of the lipoglycopeptides, a deoxymannose moiety. Herein, we report the first total synthesis of a member of this group of antibiotics, arylomycin A2. The synthesis relies on Suzuki-Miyaura-mediated biaryl coupling, which model studies suggested would be more efficient than a lactamization-based route. Biological studies demonstrate that these compounds are promising antibiotics, especially against Gram-positive pathogens, with activity against S. epidermidis that equals that of the currently prescribed antibiotics. Structural and biological studies suggest that both N-methylation and lipidation may contribute to antibiotic activity, whereas glycosylation appears to be generally less critical. Thus, these studies help identify the determinants of the biological activity of arylomycin A2 and should aid in the design of analogs to further explore and develop this novel class of antibiotic.     

Synthesis and characterization of mixed-ligand copper(II) saccharinate complexes containing tridentate NNS Schiff bases. X-ray crystallographic analysis of the free ligands and one complex

Four new Schiff bases containing N and S heteroatoms (HL1–HL4) have been prepared and characterized, including determination of the X-ray crystal structures of HL1 and HL3. Spectroscopic evidence indicates that these Schiff bases behave as uninegatively charged tridentate NNS ligands in complexes of general formula [Cu(Ln)sac] (Ln is the anionic form of NNS, and sac represents saccharinate anion). Crystals of both HL1 and [Cu(L4)sac)(H₂O)]·Hsac crystallized in triclinic system with P $ \bar{1} $ space group, while HL3 crystallized in monoclinic system with P 2₁/c space group. [Cu(L4)sac)(H₂O)]·Hsac has a distorted square-pyramidal structure with a non-bonded saccharin molecule present in the outer coordination sphere. The tridentate NNS ligands are coordinated to Cu through pyridine nitrogen, azomethine nitrogen and thiolate sulfur atoms, while the fourth and fifth coordination positions are occupied by the N-bonded saccharinate anion and a water ligand, respectively.     

Synthesis and crystallographic characterization of multi-donor N-heterocyclic carbene chelating ligands and their silver complexes: Potential use in pharmaceuticals

The potential for N-heterocyclic carbenes (NHCs) to be used as novel chelating ligands for bio-inorganic pharmaceuticals is discussed. In this paper, we design, synthesize and characterize two NHC precursors, 6 and 7, that we believe have potential for use as metal chelators for pharmaceuticals. The NHC precursors are composed of imidazolium and pyridine rings that would form mixed donor NHCs upon metallation with medicinally relevant metals. The exploration of the silver chemistry of 6 yielded the dimeric silver NHC complex 8[BPh₄]₂. The study of the silver chemistry of 7 gave 9[1/3(Ag₄Br₇)] and 10[NO₃]₃. Complex 9[1/3(Ag₄Br₇)] appears to be a silver biscarbene charge balanced by a silver bromide anionic cluster. Complex 10[NO₃]₃ is a trinuclear silver cluster that is stabilized by NHCs and pyridine rings. Silver NHCs have shown themselves to be excellent transmetallation agents for access to other metal NHC systems. It is envisioned that the silver NHCs 8[BPh₄]₂, 9[1/3(Ag₄Br₇)] and 10[NO₃]₃ will readily transfer to medicinally relevant metals, such ¹⁰⁵Rh.     

Synthesis and X-ray crystallographic and IR spectroscopic study of complex alkaline earth zirconium arsenates

Arsenates A_0.5Zr₂(AsO₄)₃ (A = Mg, Ca, Sr, Ba), synthesized through sol–gel route with subsequent heat treatment, have been studied by X-ray diffraction, electron probe microanalysis, and IR spectroscopy. Mg_0.5Zr₂(AsO₄)₃ crystallizes in the Sc₂(WO₄)₃ structure type (space group P2₁/n). A_0.5Zr₂(AsO₄)₃ (A = Ca, Sr, Ba) crystallize in the NaZr₂(PO₄)₃ structure type (space group \(R\bar 3\)). The Ca_0.5Zr₂(AsO₄)₃ and Ba_0.5Zr₂(AsO₄)₃ structures have been refined by the full-profile analysis. The structure frameworks are composed of ZrO₆ octahedra and AsO₄ tetrahedra. The alkaline earth metal atoms occupy one of the two extraframework positions inside the structure columns. The internal vibrational frequencies of the AsO₄ ^3- tetrahedron have been assigned. The number of the observed bands corresponds to the number predicted by the factor group analysis of vibrations for space groups \(R\bar 3\) and P2₁/n.     

Synthesis and characterization of new nitridotechnetium-EDTA complex

TcN-EDTA has been synthesized for the first time starting from TcNCl₄ ^–. Elemental analysis shows that this compound has three molecules of water of crystallization: TcN(Hedta) · 3H₂O. Its optical spectrum has an absorption maximum at 505 nm with = 1060 dm³.mol^–1.cm^–1. It decomposed easily under alkaline conditions.     

Synthesis,Characterization, and crystallographic analysis of some benzoimidazole derivatives

A number of benzenesulfonyl derivatives of benzoimidazol-2-ylamine and 1-methyl-benzoimidazol-2-ylamine were synthesized, their synthesis reactions under different experimental conditions being monitored by hptlc. The crystal and molecular structures of N-(1-benzenesulfonyl-1,3-dihydrobenzoimidazol-2-ylidene)benzenesulfonamide (4) and N-(1-benzenesulfonyl-3-methyl-1,3-dihydro-benzoimidazol-2-ylidene)-benzenesulfonamide (7) were determined by X-ray diffraction analysis. The structure of compound 4 is made up of two crystallographically independent molecules and that of compound 7 of one molecule. In both cases, the structure contains the imido form of the molecules. There are strong conjugative effects between the imido groups and the imidazolic rings. Weak intramolecular C? H···O hydrogen bonding interactions could influence the molecular conformations.     

酪氨酸修饰新型手性卟啉配合物的合成与表征

利用亲核取代反应合成了一种L-酪氨酸修饰的新型手性自由卟啉(5-[2-(L-酪氨酸)乙氧基苯基]-10,15,20-三苯基卟啉)及其对应的金属锌卟啉(5-[2-(L-酪氨酸)乙氧基苯基]-10,15,20-三苯基锌卟啉).通过元素分析、紫外-可见光谱、核磁共振氢谱、圆二色谱、红外光谱、荧光光谱等多种谱图对合成的目标化合物进行了表征.     

Synthesis and crystallographic characterization of chiral bis-oxazoline-amides. Fine-tunable ligands for Pd-catalyzed asymmetric alkylations

New chiral chelating C2 bis-oxazoline-amide ligands (1) exhibiting a highly flexible molecular structure have been prepared in high yield through a versatile synthetic pathway. Combined crystallographic, variable temperature (VT)-NMR, IR, and ESI-MS studies have been carried out to investigate the nature of the 1-Pd complexes that are effective tools in controlling the stereochemical outcome of Pd-catalyzed allylic alkylations (ee up to 98%).     

Synthesis and crystallographic characterization of a ‘palladadehydrobenzo[19]annulene’

The trans-palladium bis(σ-acetylide) complex (Et₃P)₂Pd(C₃₀H₁₂) (2) was synthesized from hexane 4 in 77% yield via a simple three-step process. The X-ray crystal structure of 2 shows a strained and warped annulenic core upon insertion of the organometallic fragment. UV-vis data of the molecule suggest limited electronic delocalization throughout the metallacycle.     

8-羟基喹啉铋的合成、表征与光谱研究

8-羟基喹啉及其衍生物是以喹啉环为母体的化合物,具有较大的共轭π键结构,吸光系数高,分子中处于邻位的羟基O和杂环N原子上都含有孤对电子,与金属离子易形成双齿配位具有特殊光学特性的五员环配合物[1-3].金属铋被认为是安全稳定的绿色重金属元素,其化合物除了广泛应用于医学外,其配合物的用途正日益被开发[4-5].本文用元素分析仪、XRD、热重-差热、红外等手段对由8-羟基喹啉形成的铋配合物的组成和结构进行表征.并初步研究了生成物的光致发光性和紫外吸收光谱.     

Synthesis and X-ray crystallographic analysis of chiral pyridyl substituted carbocyclic molecular clefts

Ditopic symmetrical bis(pyridyl) ligands incorporating the chiral dibenzobicyclo[b,f][3.3.1]nona-5a,6a-diene-6,12-dione cleft have been synthesised and characterised by NMR spectroscopy, mass spectrometry and X-ray crystallography. The ligands, which incorporate pyridyl groups directly connected to the carbocyclic cleft core or via alkyne or phenyl linkers were accessed from palladium-catalysed coupling reactions of 2,8-dibromodibenzobicyclo[b,f][3.3.1]nona-5a,6a-diene-6,12-dione. X-ray crystal analyses show the interplanar angles between the two cleft aromatic rings in these molecules, which range from 97.80(3) to 109.80(4)°.     

Synthesis and crystallographic analysis of short pyridine-based oligoamides as DNA-targeting supramolecular binders

In this study, the synthesis of the pyridine peptides 1–4, formed from amino-picolinic acid, and pyridine peptide 5, made from coupling of a mono-protected pyridine diamine to a mono-protected pyridine dicarboxylic acid and the X-ray crystallographic structures of 1 and 5 are discussed, along with their supramolecular interactions in the solid state. The structure of these compounds showed that they possess concave appearance which can be employed to bind to nucleic acids through multiple hydrogen bonding, which would facilitate the formation of helical-based pyridine oligoamides as novel DNA-binding molecules. This was proven by carrying out DNA denaturation studies and ethidium displacement assay on 5, but, by using MTT assays, 5 was shown to be cytotoxic against drug-resistant chronic myeloid leukaemia K562 cell-line.

     

Synthesis and characterization of a platinum(II) complex with N-acetyl-L-cysteine

Synthesis and spectroscopic studies in the solid-state of a platinum(II) complex with N-acetyl-L-cysteine are described. Elemental analyses are consistent with composition Pt₂(C₅H₈NO₃S)₄ · 3H₂O. Solid-state ¹³C NMR, infrared, and U-Vis spectroscopic results are consistent with coordination of the ligand to platinum(II) through sulfur. Thermal analyses confirmed water in the complex composition. Final residue of the thermal treatment was identified by powder X-ray diffractometry as metallic platinum.     

Synthesis, spectroscopic characterization and biological analysis of a new palladium(II) complex with methionine sulfoxide

A new palladium(II) complex with methionine sulfoxide was synthesized and characterized by a set of chemical and spectroscopic techniques. Elemental and mass spectrometry analyses of the solid complex fit to the composition [Pd(C5H10NO3S)2].H2O. 13C NMR, [1H-15N] NMR and infrared spectra indicate coordination of the amino acid to Pd(II) through the carboxylate and amino groups in a square planar geometry. The complex is soluble in water. Biological activity was evaluated by cytotoxic analysis using HeLa cells. Determination of cell death was assessed using a tetrazolium salt colorimetric assay, which reflects the cells viability. After incubation for 48 h, 20% of cell death was achieved at a concentration of 200 micromol L-1 of the complex.     

Structure-based virtual screening of dipeptidyl peptidase 4 inhibitors and their in vitro analysis

Type 2 diabetes mellitus (T2DM) is one of the most widely prevalent metabolic disorders with no cure to date thus remains the most challenging task in the current drug discovery. Therefore, the only strategy to control diabetes prevalence is to develop novel efficacious therapeutics. Dipeptidyl Peptidase 4 (DPP-4) inhibitors are currently used as anti-diabetic drugs for the inhibition of incretins. This study aims to construct the chemical feature based on pharmacophore models for dipeptidyl peptidase IV. The structure-based pharmacophore modeling has been employed to evaluate new inhibitors of DPP-4. A four-featured pharmacophore model was developed from crystal structure of DPP-4 enzyme with 4-(2-aminoethyl) benzenesulfonyl fluoride in its active site via pharmacophore constructing tool of Molecular Operating Environment (MOE) consisting F1 Hyd (hydrophobic region), F2 Hyd|Cat|Don (hydrophobic cationic and donor region), F3 Acc (acceptor region) and F4 Hyd (hydrophobic region). The generated pharmacophore model was used for virtual screening of in-house compound library (the available compounds which were used for initial screening to get the few compounds for the current studies). The resultant selected compounds, after virtual screening were further validated using in vitro assay. Furthermore, structure-activity relationship was carried out for the compounds possessing significant inhibition potential after docking studies. The binding free energy of analogs was evaluated via molecular mechanics generalized Born surface area (MM-GBSA) and Poisson-Boltzmann surface area (MM-PBSA) methods using AMBER 16 as a molecular dynamics (MD) simulation package. Based on potential findings, we report that selected candidates are more likely to be used as DPP-4 inhibitors or as starting leads for the development of novel and potent DPP-4 inhibitors.     

Synthesis, characterization and antioxidant activity copper-quercetin complex

Quercetin (3,3',4',5,7-pentahydroxyflavone) one of the most abundant dietary flavonoids, has been investigated in the presence of Cu(II) in methanol. The spectroscopic studies (UV-vis, (1)H NMR and IR) were useful to assess the relevant interaction of Quercetin with Cu(II) ions, the chelation sites and dependence of the complex structure from the metal/ligand ratio. A 1:2 (L:M) complex was indicated by Job's method of continuous variation, which was applied to ascertain the stoichiometric composition of the complex. The antioxidant activities of the compounds were evaluated by using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method. The complexed flavonoid was much more effective free radical scavengers than the free flavonoids.     

Salen-iron complexes: Synthesis,characterization and their reactivity with lactide

Schiff-base metal complexes as efficient catalysts are widely used in ring-opening polymerization of cycle esters.The salen Fe complexes were formed with their excellent biocompatibility and less toxicity.A series of salen Fe complexes were designed in this work in order to study the activity and control of polymerization of lactide.The salen Fe complexes' activities changed with the ligands configuration and substituent groups.