Biosynthesis‐Assisted Structural Elucidation of the Bartolosides,Chlorinated Aromatic Glycolipids from Cyanobacteria

The isolation of the bartolosides, unprecedented cyanobacterial glycolipids featuring aliphatic chains with chlorine substituents and C‐glycosyl moieties, is reported. Their chlorinated dialkylresorcinol (DAR) core presented a major structural‐elucidation challenge. To overcome this, we discovered the bartoloside (brt) biosynthetic gene cluster and linked it to the natural products through in vitro characterization of the DAR‐forming ketosynthase and aromatase. Bioinformatic analysis also revealed a novel potential halogenase. Knowledge of the bartoloside biosynthesis constrained the DAR core structure by defining key pathway intermediates, ultimately allowing us to determine the full structures of the bartolosides. This work illustrates the power of genomics to enable the use of biosynthetic information for structure elucidation.     

Biosynthesis‐Assisted Structural Elucidation of the Bartolosides,Chlorinated Aromatic Glycolipids from Cyanobacteria

The isolation of the bartolosides, unprecedented cyanobacterial glycolipids featuring aliphatic chains with chlorine substituents and C‐glycosyl moieties, is reported. Their chlorinated dialkylresorcinol (DAR) core presented a major structural‐elucidation challenge. To overcome this, we discovered the bartoloside (brt) biosynthetic gene cluster and linked it to the natural products through in vitro characterization of the DAR‐forming ketosynthase and aromatase. Bioinformatic analysis also revealed a novel potential halogenase. Knowledge of the bartoloside biosynthesis constrained the DAR core structure by defining key pathway intermediates, ultimately allowing us to determine the full structures of the bartolosides. This work illustrates the power of genomics to enable the use of biosynthetic information for structure elucidation.     

Porous,Conductive Metal‐Triazolates and Their Structural Elucidation by the Charge‐Flipping Method

A new family of porous crystals was prepared by combining 1H‐1,2,3‐triazole and divalent metal ions (Mg, Mn, Fe, Co, Cu, and Zn) to give six isostructural metal‐triazolates (termed MET‐1 to 6). These materials are prepared as microcrystalline powders, which give intense X‐ray diffraction lines. Without previous knowledge of the expected structure, it was possible to apply the newly developed charge‐flipping method to solve the complex crystal structure of METs: all the metal ions are octahedrally coordinated to the nitrogen atoms of triazolate such that five metal centers are joined through bridging triazolate ions to form super‐tetrahedral units that lie at the vertexes of a diamond‐type structure. The variation in the size of metal ions across the series provides for precise control of pore apertures to a fraction of an Angstrom in the range 4.5 to 6.1 Å. MET frameworks have permanent porosity and display surface areas as high as some of the most porous zeolites, with one member of this family, MET‐3, exhibiting significant electrical conductivity.     

Microwave‐Assisted Dibromoolefination of Aromatic and Heteroaromatic Aldehydes and Ketones

Microwave (MW) irradiation was successfully employed to convert aromatic and heteroaromatic aldehydes and ketones efficiently to the corresponding dibromoolefins. Exemplified by the successful dibromoolefination of traditionally inert pyridyl‐flanked carbonyls, MW activation significantly broadens the scope of this valuable transformation, although some limitations especially with electron‐rich aromatic ketone derivatives remain.     

Triazole‐Assisted Ruthenium‐Catalyzed CH Arylation of Aromatic Amides

Site‐selective ruthenium(II)‐catalyzed direct arylation of amides was achieved through C?H cleavages with modular auxiliaries, derived from easily accessible 1,2,3‐triazoles. The triazolyldimethylmethyl (TAM) bidentate directing group was prepared in a highly modular fashion through copper(I)‐catalyzed 1,3‐dipolar cycloaddition and allowed for ruthenium‐catalyzed C?H arylations on arenes and heteroarenes, as well as alkenes, by using easy‐to‐handle aryl bromides as the arylating reagents. The triazole‐assisted C?H activation strategy was found to be widely applicable, to occur under mild reaction conditions, and the catalytic system was tolerant of important electrophilic functionalities. Notably, the flexible triazole‐based auxiliary proved to be a more potent directing group for the optimized ruthenium(II)‐catalyzed direct arylations, compared with pyridyl‐substituted amides or substrates derived from 8‐aminoquinoline.     

Structural Elucidation and Antitumor Activity of Polysaccharide AMP-1 from Atractyloids macrocephalae K.

A polysaccharide named as AMP‐1 was isolated from the root of Atractylodis macrocephalae Koidz, and purified by ethanol fractionation and gel filtration. The homogeneity of AMP‐1 was determined by HPLC and capillary electrophoresis that gave a single peak. AMP‐1 is composed of galactose and mannose in a molar ratio of 1.0:1.9. Its molecular weight is 3.8 × 10³. The structure of ghycan was elucidated by IR, ¹H NMR, ¹³C NMR and methylation analysis, and on the basis of the results was suggested that AMP‐1 contain a backbone of β. (1–2)‐D‐galactose residues with branches of single β‐D‐mannose residue being substituted at the O‐6. Bioactivity assay of AMP‐1 showed that it could inhibit growth of Sarcoma 180 and Lewis pulmonary carcinoma implanted in mice.     

The Impact of Long‐Range 1H‐15N Heteronuclear Shift Correlation Data on Computer‐Assisted Structure Elucidation: Posaconazole

Considerable work has been invested in the area of computer‐assisted structure elucidation (CASE) methods. As NMR techniques have been developed that provide more effective atom‐to‐atom connectivity information, it has become theoretically possible to do de novo structure elucidation based on 2D NMR datasets recorded for an unknown molecule. However, as annular (ring) nitrogen atoms become more prevalent in complex chemical structures, the ability to rely solely on ¹H and ¹³C homo‐ and hetero‐nuclear direct and long‐range connectivity information to solve a structure correspondingly diminishes. Hence, we now wish to report the results of an investigation into the application of CASE methods with and without long‐range ¹H‐¹⁵N data using posaconazole as a model compound, which has eight annular nitrogens in its structure. With the inclusion of ¹H‐¹⁵N data long‐range data, the structure could be successfully determined in a few hours. Excluding the ¹H‐¹⁵N data caused the program to generate millions of candidate structures, none of which fit the data well enough to be stored.     

Study of Nanocrystalline BiMnO3‐‐PbTiO3: Synthesis,Structural Elucidation,and Magnetic Characterization of the Whole Solid Solution

In the last ten years, the study and the search for new multiferroic materials have been a major challenge due to their potential applications in electronic technology. In this way, bismuth‐containing perovskites (BiMO₃), and particularly those in which the metal M position is occupied by a magnetically active cation, have been extensively investigated as possible multiferroic materials. From the point of view of synthesis, only a few of the possible bismuth‐containing perovskites can be prepared by conventional methods but at high pressures. Herein, the preparation of one of these potential multiferroic systems, the solid solution xBiMnO₃‐(1?x)PbTiO₃ by mechanosynthesis is reported. Note that this synthetic method allows the oxides with high x values, and more particularly the BiMnO₃ phase, to be obtained as nanocrystalline phases, in a single step and at room temperature without the application of external pressure. These results confirm that, in the case of Bi perovskites, mechanosynthesis is a good alternative to high‐pressure synthesis. These materials have been studied from the point of view of their structural characteristics by precession electron diffraction and magnetic property measurements.     

Microwave‐Assisted and Ultrasonic‐Assisted Three‐Component Heterocyclization of 4‐Amino‐5‐carboxamido‐1,2,3‐triazole,Thiopyran‐3‐one‐1,1‐dioxide,and Aromatic Aldehydes

Three‐component heterocyclization of 4‐amino‐5‐carboxamido‐1,2,3‐triazole, thiopyran‐3‐one‐1,1‐dioxide, and aromatic aldehydes under ultrasonic and microwave irradiation was studied. Regardless of the reaction parameters, 5,6,7,9‐tetrahydro‐4H‐thiopyrano[3,2‐d][1,2,3]triazolo[1,5‐a]pyrimidine‐8,8‐dioxides were isolated as sole reaction products whose structures were proven with help of NMR data and X‐ray analysis.     

Structural Aspects of the β‐Polymorph of (E)‐4‐Formylcinnamic Acid: Structure Determination Directly from Powder Diffraction Data and Elucidation of Structural Disorder from Solid‐State NMR

Among the derivatives of (E)‐cinnamic acid for which the solid‐state photochemical properties have been studied, (E)‐4‐formylcinnamic acid ( 1 ) has already received much attention. Given the inability to prepare single crystals of the β‐polymorph of 1 that are of suitable size and quality for structural characterization by single‐crystal X‐ray diffraction, the structure of this material was determined directly from powder X‐ray‐diffraction data by means of the genetic‐algorithm technique for structure solution, followed by Rietveld refinement. High‐resolution solid‐state ¹³CNMR was also applied to elucidate details of structural disorder concerning the orientation of the formyl group, and provided independent support for the disorder model established form the Rietveld refinement. The reported structure establishes that the β‐phase of 1 is not structurally anomalous among photoreactive (E)‐cinnamic acid crystals, and finally resolves a long‐standing controversy concerning the structural properties of this material.     

Palladium‐Assisted “Aromatic Metamorphosis” of Dibenzothiophenes into Triphenylenes

Two new palladium‐catalyzed reactions of aromatic sulfur compounds enabled the conversion of dibenzothiophenes into triphenylenes in four steps. This transformation of one aromatic framework into another consists of 1) 4‐chlorobutylation of the dibenzothiophene to form the corresponding sulfonium salt, 2) palladium‐catalyzed arylative ring opening of the sulfonium salt with a sodium tetraarylborate, 3) an intramolecular S_N2 reaction to form a teraryl sulfonium salt, and 4) palladium‐catalyzed intramolecular C? S/C? H coupling through electrophilic palladation. Symmetrical as well as unsymmetrical triphenylenes of interest were synthesized in a tailor‐made fashion in satisfactory overall yields.     

Cocrystal Formation through Mechanochemistry: from Neat and Liquid‐Assisted Grinding to Polymer‐Assisted Grinding

Mechanochemistry is an effective method for the preparation of multicomponent crystal systems. In the present work, we propose an alternative to the established liquid‐assisted grinding (LAG) approach. Polymer‐assisted grinding (POLAG) is demonstrated to provide a new class of catalysts for improving reaction rate and increasing product diversity during mechanochemical cocrystallization reactions. We demonstrate that POLAG provides advantages comparable to the conventional liquid‐assisted process, whilst eliminating the risk of unwanted solvate formation as well as enabling control of resulting particle size. It represents a new approach for the development of functional materials through mechanochemistry, and possibly opens new routes toward the understanding of the mechanisms and pathways of mechanochemical cocrystal formation.     

A Facile Microwave‐Assisted “One‐Pot” Synthesis of Piperazino Pyrimidinyl Acetamides,a Class of Hybrid Bis Heterocycles and Their Structural Elucidation Using NMR Spectral Techniques

An array of novel piperazino pyrimidinyl acetamides, a class of hybrid bis heterocycles are synthesized in “one‐pot” by microwave irradiation method catalyzed by heterogeneous NaHSO₄.SiO₂ catalyst in dry media and are characterized by melting point, elemental analysis, MS, FT‐IR, one‐dimensional NMR (¹H and ¹³C) and two‐dimensional ¹H‐¹H COSY and ¹H‐¹³C HSQC spectral data.     

Development of the Headspace SPME/ATR‐IR Method for Detection of Chlorinated Aromatic Compounds in Soils

In this paper, a new method based on attenuated total reflection infrared (ATR‐IR) spectroscopy was developed to detect chlorinated aromatic compounds in soil. To eliminate the problems associated in inspection of soil samples by the ATR‐IR method, chlorinated compounds were evaporated from soil matrices and detected in the headspace. The sensing device was constructed by an internal reflection element (IRE) coated with a hydrophobic film to attract and concentrate chlorinated compounds evaporated to the headspace. Factors that influence the analytical signals were studied such as the moisture content, volatilities of analytes, and effect of heating temperature. Results indicated that the addition of thermal energy to the soil sample resulted in an increase of IR signal. However, the IRE was also warmed up and caused a slight decrease of the IR signals after a long detection time. The studies of the influence of moisture indicated that a small amount of water present in soils could tremendously increase the intensity of detected IR signals. The further increase of moisture contents resulted in a decrease of the analytical signals, and the optimal signal was found when soil samples contained 5% (v/w) water. Results in analyses of compounds with different volatilities indicated that even with vapor pressure lower than 0.017 Torrs, quality IR spectra could still be obtained. Using the optimal conditions found in this work, the results in determination of five compounds in soil samples indicated that the linear regression coefficients (R‐square) were higher than 0.992 with detection limits around a few hundreds of ppb.