Synthesis and characterization of 1,8-naphthalimide with [6]helicene skeleton

A 1,8-naphthalimide with [6]helicene derivative scaffold has been designed and synthesized. The (P)- and (M)-enantiomers of the [6]helicene derivative were resolved by HPLC on a chiral column. The single crystal of the [6]helicene derivative exhibits an intermolecular interactions of the 1,8-naphthalimide units.     

Synthesis,X-ray analysis and photophysical properties of a new N-containing pentacyclic helicene

A new helically chiral pentacyclic system containing one pyrrole ring was prepared in a good yield and purity via a three-step sequence involving Heck coupling and classical oxidative photocyclization. X-ray crystal structure analysis indicated that the conformation resembled that of unsubstituted pentahelicene, the idealized symmetry of which is C₂. The optical properties of the pentacyclic helicene were investigated and show interesting behaviour.     

Synthesis of hexacyclic parnafungin A and C models

A convergent, practical route to unstable hexacyclic parnafungin A and C models has been developed. Two iodoxanthones were prepared in four or five steps (33-50% overall yield). Suzuki-Miyaura coupling of the iodoxanthones with excess readily available 3-carbomethoxy-2-nitrophenyl pinacol boronate afforded the hindered highly functionalized 2-arylxanthones (53-58%) in the first key step. In the second key step, zinc reduction gave benzisoxazolinones that were treated with MsCl and then base to generate the unstable hexacyclic parnafungin A (13% overall yield for 8 steps) and C (8% overall yield for 9 steps) models. Analogously to the parnafungins, hexacyclic parnafungin C model decomposes to a phenanthridine with a half-life of 2 d in CDCl(3).     

Synthesis and self-aggregation of cyclic alkynes containing helicene

[structure: see text]. All stereoisomers of a cyclic alkyne containing three helicene units, 1,12-dimethylbenzo[c]phenanthrene, are synthesized using a building block. Isomeric [3 + 3]cycloalkynes aggregate in organic solvents. Vapor pressure osmometry reveals dimer formation of (M,M,M)-[3 + 3]cycloalkynes in chloroform and benzene at concentrations above 2 mM. No higher aggregation is observed. The chirality of helicenes plays an important role in self-aggregation, and diastereomeric (M,P,M)-[3 + 3]cycloalkyne forms a dimer only above 15 mM. Aggregation of racemic (M,M,M)-[3 + 3]cycloalkyne or (M,P,M)-[3 + 3]cycloalkyne is much weaker than that of a single enantiomer.     

Synthesis and properties of an aggregating heterocyclic helicene.

Heterohelicene 10 is synthesized in six steps from 3,3'-bithienyl. Because the number of steps is small, because the yield is 95% in the last (the reaction of a bis-enol ether with 1,4-benzoquinone-a six-step one pot procedure that constructs the helicene skeleton), and because chromatography is not required to purify any of the products in the synthesis, significant amounts are easily prepared. To convert 10 into enantiopure 3, a helicenebisquinone surrounded by four dodecyloxy groups, requires only a precedented three-step sequence. Enantiopure helicene 3, either without solvent or in dodecane (but not in chloroform) aggregates into columnar structures whose optical properties differ markedly from those of the monomer but resemble those shown previously only by aggregates of 1. Evidence of aggregation in the pure material includes optical microscopic observation of long fibrous structures and X-ray diffraction and combined transmission electron microscopic and electron diffraction analyses showing the molecules within the fibers to be organized in columnar arrays. The circular dichroism spectra, specific rotations, and fluorescent emission spectra of the aggregated structures are all distinctive, and, as reported elsewhere, the second harmonic response is very large. The linear polarizations of the monomers' and aggregates' fluorescent emissions differ greatly. The circular polarization of the aggregates' fluorescent emission, after excitation by unpolarized light, is large.     

Synthesis and structure of built-up organic macromolecules containing helicene

Built-up macromolecules are acyclic molecules with molecular weights of several thousand daltons, which are synthesized by connecting small molecular units using stepwise methods. The chemical study of built-up macromolecules reveals some noteworthy properties that are different from those of conventional biological and synthetic macromolecules. A characteristic feature of built-up organic macromolecules is that their structures and properties are discontinuous at a certain molecular weight. For such macromolecules, variation in the small molecular units and the formation of cyclic structures substantially affect the structure and properties. The built-up organic macromolecules obtained by connecting helicenes with amide, acetylene, and amine groups are discussed in this paper. Some chiral built-up macromolecules are linked by covalent bonds, and the effects of linking on the structure are compared.     

Synthesis and characterization of a new modification of PtAl

A new PtAl phase, which is stable at room temperature under oxidizing conditions, has been synthesized at 200 °C and 5 MPa. X‐ray studies reveal it to be different from the known polymorphs of PtAl, which crystallize in the FeSi and CsCl structure types. The crystal structure of the new PtAl modification is found to be isotypical with the low‐temperature modification of PdAl. In situ high‐temperature X‐ray diffraction experiments in air were performed to study the thermal behavior of the new PtAl alloy. In the temperature range between 400 and 700 °C, Pt₅Al₃ forms as an intermediate phase. At higher temperature the alloy decomposes, resulting in the formation of platinum and Al₂O₃. The thermodynamic instability at high temperatures explains why this new modification has not been observed using contemporary metallurgic processes. Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis and characterization of a new layered lead borate

A new lead borate, Pb[B₈O₁₁(OH)₄], has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction, FTIR, powder X-ray diffraction and thermogravimetric analysis. The compound crystallizes in the monoclinic system, space group P2₁/n (No. 14), , , , β=90.327(2)°, , and Z=4. The structure consists of layers of 9-membered borate rings enclosing Pb²⁺ cations. Adjacent borate layers are interconnected via ionic Pb-O bonds and hydrogen bonding to form a 3D supramolecular network.     

Synthesis and characterization of a new conducting polymer composite

Organic conductive composite films have been synthesized by electropolymerization of pyrrole in the presence of chitosan and p-toluene sulfonic acid sodium salt. The obtained conductive polymer composite films have been characterized by Fourier Transform Infrared spectroscopy, dynamic mechanical analysis, scanning electron microscopy, X-ray diffraction and conductivity measurements. The prepared polymer composite films had the amorphous structure and exhibited the enhanced conductivity and mechanical properties due to the presence of chitosan in the composite films.     

Synthesis and characterization of a new silicone-based polyurethane surfactant

ω-N,N-Dihydroxyethyl aminopropylpolymethylhydrosiloxane (DAPS) a monotelechelic polydimethylsiloxane with a diol-end group, which is used to prepare polyurethane surfactant, was successfully synthesized. The preparation included four steps, which are hydroxyl protection, alkylation, hydrosilylation, and deprotection. Then, a novel silicone-based polyurethane surfactant was prepared by the addition polymerization of isophorone diisocyanate to DAPS, polypropylene glycol, and methanol and was used in the preparation of polystyrene by emulsion polymerization. The DAPS was characterized by FTIR, ¹H NMR, ¹³C NMR and elemental analysis. The results showed that each step was successfully carried out and the targeted products were synthesized in all cases.     

Synthesis and characterization of a polyoxovanadate cluster representing a new topology

A new type of mixed-valence polyoxoanionic cluster, [V(V)13V(IV)3O42(Cl)]8-, composed of 14 {VO5} square pyramids and 2 {VO4} tetrahedral units, hosting a chloride ion has been synthesized and characterized.     

Synthesis and structural characterization of a new trimetallic thiocubane cluster

The trimetallic cluster W2CuAgS4(TDT)2(PPh3)2-CH2Cl2 (TDT= [S2(C6H3)CH3]2-) (2) has been prepared from the reaction of the well-defined molecule building block [W2S4(TDT)2]2-(1) with AgNO3,CuBr and PPh3.The structure contains a [W2CuAgS4]4+ distorted cubane-like core.Two types of metal-metal bonds exist in the core.One is W-W bond of which length is 0.2871(1) nm,the other is W-M' (M'=Cu or Ag) bonds,whose mean distance is 0.2980 nm.The details of synthesis,structure,IR,UV-Vis and 31P NMR spectra are reported.The crystallographic data are:space group F21/n,with 0=1.6987(4),6=1.7763(6),c=1.8918(5) nm,β=98.54(2)°,V=5.645(3) nm3,Z=4,and final R=0.043 for 6437 observed reflections.     

Synthesis and characterization of a new fluorogenic substrate for alpha-galactosidase

Alpha-galactosidase A hydrolyzes the terminal alpha-galactosyl moieties from glycolipids and glycoproteins in lysosomes. Mutations in α-galactosidase cause lysosomal accumulation of the glycosphingolipid, globotriaosylceramide, which leads to Fabry disease. Small-molecule chaperones that bind to mutant enzyme proteins and correct their misfolding and mistrafficking have emerged as a potential therapy for Fabry disease. We have synthesized a red fluorogenic substrate, resorufinyl α-d-galactopyranoside, for a new α-galactosidase enzyme assay. This assay can be measured continuously at lower pH values, without the addition of a stop solution, due to the relatively low pK _a of resorufin (~6). In addition, the assay emits red fluorescence, which can significantly reduce interferences due to compound fluorescence and dust/lint as compared to blue fluorescence. Therefore, this new red fluorogenic substrate and the resulting enzyme assay can be used in high-throughput screening to identify small-molecule chaperones for Fabry disease. Zhen-Dan Shi and Omid Motabar contributed equally to this work     

Synthesis and characterization of a new prostaglandin H synthase model

Prostaglandin H synthases (PGHSs) are heme-containing enzymes, which directly add two O₂ molecules to arachidonic acid (AA) by the initiation of H-atom abstraction of 1,4-diene moiety and through sequential reactions to give PGH₂ as a final product. Here, we report the synthesis of a new PGHS model, which has two binaphthol bridges in one side of an iron porphyrin. Its substrate reaction site is more flexible and accordingly less hindered than the previous four binaphthol-bridged twin-coronet-type models (FeTCP). The present model is expected to accept higher olefins, which can reach the intermediate phenoxyl radical and iron in this complex. Upon treatment of the iron complex with mCPBA at −50 °C, we succeeded in the quantitative generation of the corresponding naphthoxyl radical, which was characterized by the increase in characteristic absorbance for naphthoxyl radical at 385 and 485 nm as well as by its ESR signal and recovery of the original spectra by the addition of N,N-dimethylaniline as an efficient reducing agent.     

Synthesis and characterization of a new organic-inorganic hybrid polyphosphazene polymer

A new organic-inorganic hybrid polyphosphazene polymer was synthesized via sequential nucleophilic substitution using allylamine and phenol. The polymer was characterized by FTIR, 1H-NMR, and 31P-NMR spectra. The thermal properties were studied by DSC and TGA. It was found that the polymer has good thermal stability. Char yields of the polymer reaches to 48.6% at 800 ℃. The high char yield makes it possible in theory for the polymer to be used as flame retardant. By cross linking, the thermal stability of the polymer could be improved further.     

Synthesis and characterization of a new conjugated polymer: Polytrifluoromethylacetylene

Polytrifluoromethylacetylene (PTFMA) was synthesized from trifluoromethylacetylene (TFMA) using a PdCl₂/DMF catalyst solution or the anionic initiator n-butyl lithium. Although PdCl₂ proved to be an effective catalyst for the polymerization of TFMA, long reaction times and poor yields made characterization of the resultant polymer difficult. The use of n-butyl lithium, on the other hand, resulted in high yields of PTFMA in relatively short reaction times. The results of thermal analysis and the effects of n- and p-type doping on the electrical conductivity of the polymer are discussed.     

一种新型氨羧配位剂的合成、表征及荧光性质研究

合成了氨羧配位剂-1,2-bis(4-aminophenoxy)ethane-N,N—N’,N'-tetraacetic acid(4-BAPTA),用FTIR,HNVIR、元素分析对其结构进行表征。讨论结构对紫外和荧光光谱的影响,水溶液的荧光强度随pH值和Ca^2 浓度的变化趋势。发现pH值在5-11的范围内荧光强度具有增强的趋势;Ca^2 浓度在0—50μg／25mL的范围内,荧光强度与Ca^2 浓度具有较好的线性关系。