Bioinspired Synthesis of Pulvinic Acids Including Xerocomic Acid and Fluorescence Properties of Bis-lactone Intermediates

A set of representative pulvinic acids were synthesised using a bioinspired strategy. Terphenyl-quinones (polyporic acid scaffold) were prepared via sequential Suzuki-Miyaura couplings allowing access to unsymmetrically substituted derivatives in a one-pot protocol. Subjected to the action of acetic anhydride and DMSO, quinones were converted into bis-lactone intermediates. Methanolysis and deprotection achieved the total syntheses of the corresponding pulvinic acids. Following this general strategy, symmetrical pulvinic, atromentic, variegatic acids and unsymmetrical congener pinastric, iso-pinastric, xerocomic and iso-xerocomic acids were prepared in fair yields. Fluorescence properties were observed for the bis-lactone intermediates and, as a complement to this synthetic work, optical properties were measured, and fluorescence quantum yields were determined for the bis-lactone pigments.     

Bis(imino)carbazolate: A Master Key for Barium Chemistry

Reported here is a readily available bis(imino)carbazole‐based proligand that constitutes a convenient entry point into the challenging synthetic molecular chemistry of barium. It enables the preparation of rare or even, up to now, unknown, solution‐stable heteroleptic barium complexes. The syntheses and structural features for the first molecular barium fluoride and the first barium stannylide, with an unsupported Ba?Sn bond, are described, along with other carbazolate barium species: an amide (both a remarkably stable starting material and an excellent hydrophosphination precatalyst), iodide, and silanylide. DFT analysis of bonding patterns in the barium stannylide and barium silanylide highlights a prevailingly ionic barium–tetrelide bond with a small covalent contribution.     

Imidodiphosphorsäuretetraphenylester,Salze und Komplexe

Tetraphenyl Imidodiphosphate, Salts, and Complexes An improved preparation of pure tetraphenyl imidodiphosphate and the preparation of the sodium, diethylammonium, barium and calcium salts of tetraphenyl imidodiphosphate are described. The syntheses of bis(tetraphenylimidodiphosphato)copper(II) and tris(tetraphenylimidodiphosphato)iron(III) are reported. The new compounds are characterized by their properties and nmr spectra. An X-ray crystal structure analysis is reported for the copper complex.     

磷酸二氢铵转化法测定硫酸钡含量

针对目前重晶石中硫酸钡含量测定方法研究不多、进展缓慢的问题,提出了一种对重晶石预处理后测定硫酸钡的方法,采用磷酸二氢铵与重晶石在700℃发生复分解反应,将不溶于水且不溶于酸的硫酸钡转化为可溶于酸的磷酸钡盐,最后依据确定的磷钡比关系,根据总磷含量间接得到钡含量。实验结果表明,磷酸二氢铵与硫酸钡的物质的量之比为2.0,并在700℃的条件下高温煅烧,可使硫酸钡全部转化完全,形成偏磷酸钡,再经过氢氧化钠、双氧水处理,转变为正磷酸氢钡并溶于盐酸中,与喹钼柠酮试剂形成磷钼酸喹啉沉淀,根据沉淀质量可准确计算出样品中硫酸钡的含量。测定的结果准确、方法可行。对测定重晶石中硫酸钡的含量提出一种新的思路和解决方案,具有实际意义。     

Solvent-Free Organic Syntheses

Ecological points of view must nowadays be taken into consideration in the development of new syntheses and apportioned due importance in assessing the viability of a new synthesis. A crucial factor here is the need to restrict the use of ecologically harmful organic solvents. Examples are presented which show that solvent-free reactions are not only of interest from an environmental viewpoint, but also offer considerable advantages in terms of yield, selectivity, and simplicity of the reaction procedures.     

Precipitation of barium chromate from homogeneous solution using complexation and replacement A separation of barium from relatively large amounts of strontium and lead

A new procedure is presented that efficiently separates barium from relatively large amounts of strontium and lead. The barium is precipitated as the chromate from a solution in which the multivalent cations are complexed with EDTA. The barium ions are homogeneously released in solution when magnesium ions are slowly introduced into the solution. The magnesium ions gradually replace the barium ions from their EDTA complexes, bringing about a precipitation of barium chromate from homogeneous solution.

This slow formation of barium chromate crystals holds co-precipitation to a minimum and produces crystals that are easily filtered and washed. More than 99.7% of the barium can be precipitated as the chromate, with less than 0.6% of the strontium, when the two ions are in equal molar concentration.     

Biomimetic syntheses of syncarpurea

Simple syntheses of syncarpurea (1) from syncarpic acid and the amino acids ornithine or citrulline are presented.     

原位诱导生长法制备单分散M型钡铁氧体亚微空心球

提出了一种制备单分散M型钡铁氧体空心球的新方法,即以碳酸胍表面改性的单分散聚(苯乙烯-共-丙烯酸)P(St-co-AA)乳胶粒子为模板,在其表面原位诱导钡铁氧体前驱物的定位并生长,以此获得壳层均匀致密的P(St-co-AA)/钡铁氧体前驱物核壳复合粒子,再经过热处理得到结构完整、成分单一的M型钡铁氧体空心球.     

Lone-pair self-containment in tellurite tubes: hydrothermal syntheses and structures of BaTe(3)O(7) and BaTe(4)O(9)

The hydrothermal syntheses and single-crystal structures of BaTe3O7 and BaTe4O9 are reported. These closely related new phases, which can be regarded as the n = 3 and 4 members of the BaTenO2n+1 family, are built up from infinite, tubular, columns of Te/O polyhedra (6 ring loops for BaTe3O7 and 8 ring loops for BaTe4O9) with barium cations completing the structures. The tubes represent a novel way to accommodate the lone pair of electrons associated with each TeIV species and suggest the possibility of redox intercalation chemistry for these types of material.     

Study on the preparation and formation mechanism of barium sulphate nanoparticles modified by different organic acids

This paper reports a simple method to prepare barium sulphate nanoparticles by use of tetradecanoic acid, hexadecanoic acid and stearic acid as modifier. The barium sulphate nanoparticles obtained are characterized by using Fourier transform infra-red spectroscopy (FT-IR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic laser light scatter (DLLS) and thermogravimetric analysis (TGA), respectively. The results show that the BaSO₄ particles are all spherical and in the nano-scale. Our method has a better dispersion and controllable diameter dependent on the length of the chain of organic acid and the pH value of the system. A possible mechanism is also discussed.     

The one-pot synthesis of 4-aryl-1H-1,2,3-triazoles without azides and metal catalization

In this study, a new methodology for the one-pot synthesis of 4-aryl-1H-1,2,3-triazoles from arylglyoxaldoxime semicarbazone is presented. 4-Aryl-1,2,3-triazoles were obtained in moderate to good yields via sodium dithionite and O₂, which are all efficient, safe and inexpensive reagents. This reaction is more suitable for large-scale syntheses than those using hydrazoic acid, sodium azide, or organic azides.     

Two syntheses of (-)-kainic acid via highly stereoselective zinc-ene cyclizations

Two concise, high-yielding syntheses of enantioenriched (-)-kainic acid are presented. Both routes feature a Pd-catalyzed Zn-ene cyclization that proceeds with complete diastereoselectivity. The key step can be carried out on a multigram scale, and the overall yields are among the highest to date for this marine alkaloid.     

Novel antibiotics: second generation macrocyclic peptides designed to trap Holliday junctions

Described are the syntheses of 15 macrocyclic peptides designed to trap Holliday junctions (HJs) in bacteria during site-specific and homologous recombination. This leads to inhibiting bacterial growth. These second generation macrocycles were based on the C-2 symmetrical HJ. They were synthesized using a strategy that permits elucidation of the amino acid role in binding HJs. The syntheses of these macrocycles are an important step in the development of a new class of antibiotics.     

Total syntheses of (+)-spiculoic acid A and (+)-zyggomphic acid, new marine natural products of polyketide origin

The total syntheses of both natural (+)-spiculoic acid A and (+)-zyggomphic acid, new cytotoxic marine natural products of polyketide origin, have been accomplished for the first time. These syntheses were achieved by the highly stereoselective and high-yielding intramolecular Diels-Alder reaction of a functionalized (E,E,E)-2,7,9-dodecanal derivative to construct the core tetrahydroindan-2-one skeleton. A stereocongener of (+)-spiculoic acid A, i.e., the (2R,5S,6R)-isomer, was also synthesized. The details of these total syntheses are described.     

Room-temperature biosynthesis of ferroelectric barium titanate nanoparticles

The syntheses of inorganic materials by biological systems is characterized by processes that occur close to ambient temperatures, pressures, and neutral pH, as is exemplified by biosilicification and biomineralization processes in nature. Conversely, laboratory-based syntheses of oxide materials often require extremes of temperature and pressure. We have shown here the extracellular, room-temperature biosynthesis of 4-5 nm ternary oxide nanoparticles such as barium titanate (BT) using a fungus-mediated approach. The tetragonality as well as a lowered Curie transition temperature in sub-10 nm particles was established, and the ferroelectricity in these particles was shown using Kelvin probe microscopy.     

Total synthesis of the CP-molecules (CP-263,114 and CP-225,917, phomoidrides B and A). 3. Completion and synthesis of advanced analogues

The completion of the total syntheses of the CP-molecules is reported. Several strategies and tactics, including the use of amide-based protecting groups for the homologated C-29 carboxylic acid and the use of an internal pyran protecting group scheme, are discussed. The endeavors leading to the design of new methods for the homologation of hindered aldehydes and to the isolation of a polycyclic byproduct (23), which inspired the development of a new series of reactions based on iodine(V) reagents, are described. In addition, the discovery and development of the LiOH-mediated conversion of CP-263,114 (1) to CP-225,917 (2) is described, and a mechanistic rationale is presented. Finally, a synthetic route to complex analogues of the CP-molecules harboring a maleimide moiety in place of the maleic anhydride is presented.     

哒嗪酮苷类化合物的合成研究

一些嘧啶系列的苷具有较强的生理活性,其中5-氟脲苷是有效的抗癌药物。而哒嗪与嘧啶具有同分异构关系,那么,哒嗪苷类化合物是否也有相似的生理活性呢?六十年代初,Wagner等开展了这一领域的研究;到七十年代中期,Katz等合成了与天然     

Syntheses and reactions of some new dithia[3.1.3.1 ]paracyclophanes and [2.1.2.1] paracyclophanes

The syntheses of new dithia[3.1.3.1]paracyclophanes and [2.1.2.1] paracyclophanes are presented and their NMR spectroscopic properties are described. The possibility to synthesize new twin paracyclophanes by intramolecular coupling reactions of these cyclophanes is discussed.     

Solid phase synthesis of globomycin and SF-1902 A5

The syntheses of the natural lipocyclodepsipeptide-type antibiotics globomycin and SF-1902 A(5) are reported, utilizing solid phase technology for the construction of the peptidic fragment and a new asymmetric methodology of epoxidation for the preparation of the lipidic chain. The linkage between both fragments was successfully achieved in solid phase to complete the syntheses via a macrolactonization reaction executed prior to the cleavage of the acyclic precursors from the solid support. These syntheses provide access to the rapid generation of a library of analogues via modification of the amino acid residues as well as the lipidic chain, thus facilitating the identification of new antibiotics with interesting mechanisms of action based upon the inhibition of the enzyme signal peptidase II.     

Sur quelques aspects de la polysubstitution de l'amino-2-fluorène et de l'acide amino-2-fluorène-sulfonique-7

Electrophilic sulfonation and cyclisation orientation studies were carried out with 2-aminofluorene and 2-aminofluorene-7-sulfonic acid. Positions 1 and 3 are competing. A new synthesis of 2-aminofluorene-7-sulfonic acid and the syntheses of derived sulfonamides are described.