Quantification of Cannabinoids in Cultivars of Cannabis sp. by Gas Chromatography–Mass Spectrometry

Chromatographia - In the chemical characterization of medically valued Cannabis, the present work has used a gas chromatography (GC) method coupled with mass spectrometry (MS) for identification...     

Revealing Silylation of C(sp2)/C(sp3)–H Bonds in Arylphosphines by Ruthenium Catalysis

The first aromatic C−H silylation between arylphosphines and hydrosilanes enabled by a ruthenium complex has been developed. The excellent ortho-selectivity results from a four-membered metallacyclic intermediate involving phosphorus chelation. The developed system can be extended to the benzylic C−H silylation of arylphosphines. Diverse silylated arylphosphines are produced, exhibiting broad functional group compatibility. Further functionalization of the products under mild conditions renders the formed compounds useful building blocks.     

Solvent-free and direct C(sp)–H amination of adamantanes by grinding

A facile, direct and environmentally benign conversion of C(sp³)–H bonds to C(sp³)–N bonds using substoichiometric amount of aprotic superelectrophiles polyhalomethane–AlX₃ has been achieved by grinding under solvent-free conditions at room temperature in air. It is a general and simple method for the direct amination of adamantanes, and a series of aminoadamantanes of azoles, arylamines or heteroarylamines were obtained in good to excellent yields. The advantages of this amination are atom economy, solvent-free, chemoselectivity, short reaction time and high yields.     

Enhanced Dibenzothiophene Biodesulfurization by Immobilized Cells of Brevibacterium lutescens in n-Octane–Water Biphasic System

In this study, it was the first report that the Brevibacterium lutescens CCZU12-1 was employed as a sulfur removing bacteria. Using dibenzothiophene (DBT) as the sole sulfur source, B. lutescens could selectively degrade DBT into 2-hydroxybiphenyl (2-HBP) via the “4S” pathway. In the basal salt medium (BSM) supplemented with 0.25 mM DBT and 0.5 g/L Tween-80, high desulfurization rate (100 %) was obtained by growth cells after 60 h. Furthermore, the n-octane–water (10:90, v/v) biphasic system was built for the biodesulfurization by resting cells. Moreover, a combination of magnetic nano Fe₃O₄ particles with calcium alginate immobilization was used for enhancing biodesulfurization. In this n-octane–water biphasic system, immobilized B. lutescens cells could be reused for not less than four times. Therefore, B. lutescens CCZU12-1 shows high potential in the biodesulfurization.     

Characterisation of betalain patterns of differently coloured inflorescences from Gomphrena globosa L. and Bougainvillea sp. by HPLC–DAD–ESI–MS n

In the present study, the betaxanthin (bx) and betacyanin patterns of differently coloured inflorescences from Gomphrena globosa L. and Bougainvillea sp. have been investigated in detail by applying reversed phase high-performance liquid chromatography–diode array detection (HPLC–DAD) coupled with positive ion electrospray mass spectrometry. Histidine-bx was found to be the predominant betaxanthin of Gomphrena globosa inflorescences. Furthermore, arginine-bx was detected as a novel betaxanthin, which to the best of our knowledge has not been reported as a pigment that occurs naturally so far. Dopa-bx was the major betaxanthin of Bougainvillea sp., although several minor betaxanthins were also present, including lysine-bx and putrescine-bx, novel betaxanthins hitherto not observed naturally. Remarkable differences in the betacyanin patterns between the purple, red and orange varieties were observed for both Gomphrena and Bougainvillea inflorescences. Hence, both the betacyanin profiles and the relative betaxanthin:betacyanin ratios determine the broad colour palette of Gomphrena petals and Bougainvillea bracts.     

Site-selective oxidation of unactivated C–H sp3 bonds of oleanane triterpenes by Streptomyces griseus ATCC 13273

The oxidization of unactivated C–H bonds is of great interests in the structural modification of pentacyclic triterpenes. Herein we discovered the unique capability of Streptomyces griseus ATCC 13273 to catalyze the site-selective oxidation of C-29 methyl group to carboxyl group over a range of oleanane triterpenes, oleanolic acid (1), hederagenin (2), echinocystic acid (3), quillaic acid (4) and senegenin (5). Along with this reaction the hydroxylation on C-24 and C-21 were also discovered on some substrates. As a result, eight new compounds (1c, 2a～5a and 2b～4b) among the ten metabolites were isolated. The anti-inflammatory activities of these compounds were evaluated against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 macrophages, and the products with hydroxyl group on C-21 (1c, 2b and 5a) showed significantly enhanced activities with the IC₅₀ values of 1.230, 0.078 and 0.015 μM, respectively. Thus S. griseus ATCC 13273 was further proved as a useful biocatalyst to expand the structural diversity of oleanane triterpenes for medicinal chemistry research.     

Iron-catalyzed alkenylation of cyclic ethers via decarboxylative sp(C)–sp(C) coupling

An efficient Fe(acac)₃-catalyzed decarboxylative C(sp²)–C(sp³) coupling reaction via oxidation of C–H bond adjacent to an oxygen atom has been developed successfully, in which cyclic ethers are selectively transformed into the corresponding alkenylation products with good chemical yields and excellent stereoselectivities. The mechanism was studied and the reaction was supposed to proceed through a radical oxidative coupling process.     

Gold-Catalyzed C(sp2)−C(sp) Coupling by Alkynylation through Oxidative Addition of Bromoalkynes

A gold(I)-catalyzed cascade cyclization–alkynylation of allenoates using alkynyl bromide to generate β-alkynyl-γ-butenolides was investigated. Whereas alkynyl iodides afforded significant amounts of the homo-coupling of two lactone units, alkynyl bromides led to a selective reaction, and a broad functional group tolerance was observed. Under the optimized reaction conditions, it was possible to directly synthesize a large range of β-alkynyl-γ-butenolides in moderate to good yields without the need for any external oxidant.     

Challenges in C–C bond formation through direct transformations of sp2 C–H bonds

In the past several decades, organic chemists have made significant contributions to approach direct C–H transformations. However, limited substrate scope and reaction classifications, harsh condition, and the use of noble and toxic late transition-metal catalysts typically with high loadings clogged its applications. This article summarizes our recent efforts to explore new reaction types and develop new catalytic systems in this field, which may open a new channel to consider organic synthesis from easily available chemicals.     

On the study by D.S.C. of the unexpected ice melting at 0°C of emulsified aqueous saline solutions

Firstly, the behavior of droplets (Φ ≈ 1μm) of aqueous saline solutions dispersed within an emulsifying medium and subjected to steady cooling and heating is described. Droplets undergo freezing around a temperature T¹(x) and partial ice melting and total salt melting at the eutectic temperature T_E. This melting is followed by progressive melting of the remaining ice which ceases when the equilibrium temperature (T_e(x)) ice ⇆ solution is reached. Between T_e and T¹ the droplets are undercooled. Secondly, the results obtained when water crystallization occurs versus time at a fixed temperature _C, such as T¹(x) < > _C < T_e(x) are reported. During heating following crystallization at Θ_C, an unusual ice melting at 0° and/or ice melting ending at T & >; T_e(x) is noticed on the thermogram obtained by differential scanning calorimetry of the emulsion. This shows that pure ice or at all events less concentrated solutions must be present within the emulsion. A possible mechanism of crystallization at Θ_C is proposed.     

Intramolecular C(sp3)–H Bond Oxygenation by Transition-Metal Acylnitrenoids

This study demonstrates for the first time that easily accessible transition-metal acylnitrenoids can be used for controlled direct C(sp³)-H oxygenations. Specifically, a ruthenium catalyst activates N-benzoyloxycarbamates as nitrene precursors towards regioselective intramolecular C−H oxygenations to provide cyclic carbonates, hydroxylated carbamates, or 1,2-diols. The method can be applied to the chemoselective C−H oxygenation of benzylic, allylic, and propargylic C(sp³)−H bonds. The reaction can be performed in an enantioselective fashion and switched in a catalyst-controlled fashion between C−H oxygenation and C−H amination. This work provides a new reaction mode for the regiocontrolled and stereocontrolled conversion of C(sp³)-H into C(sp³)−O bonds.     

Effect of Catalase on Biocatalytic Synthesis of Pyruvate by Enzymes from Pseudomonas sp.

Pyruvate was produced from DL-lactate by a kind of green-chemical biocatalyst --cell-free extract from bacterial strain Pseudomonas sp. SM-6. Catalase in cell-free extract, whichcould stabilize the pyruvate formed by lactate oxidase, played an important role in pyruvatepreparation. The effect of catalase in conversion process was evaluated.     

Copper-Catalyzed C(sp3)-Amination of Ketone-Derived Dihydroquinazolinones by Aromatization-Driven C−C Bond Scission

Herein, we describe the development of a copper-catalyzed C(sp³)-amination of proaromatic dihydroquinazolinones derived from ketones. The reaction is enabled by the intermediacy of open-shell species arising from homolytic C−C bond-cleavage driven by aromatization. The protocol is characterized by its operational simplicity and generality, including chemical diversification of advanced intermediates.     

Hydration behavior of C2S and C2AS nanomaterials, synthetized by sol–gel method

Hydration behavior of dicalcium silicate (C₂S) (Cement chemistry nomenclature is used where C=CaO, S=SiO₂, A=Al₂O₃, S=SO₃) and gehlenite (C₂AS), synthesized by sol–gel method was investigated by means of isothermal heat flow calorimeter at different temperatures. These phases were obtained by crystallization processing at different temperatures from their xerogels (nano-crystalline) prepared by the sol–gel method at ambient temperature. The crystallization of C₂S begins below 600°C and it is well crystallized at 900°C. X-ray diffraction patterns reveal that β-C₂S is formed and it remains stable since after slow cooling. The crystallization of C₂AS xerogels starts with the formation of C₂S, then it reacts with alumina to form mineral C₂AS at 1100°C. The effect of hydration temperature upon the hydration reaction of C₂S obtained at 600 and 900°C and C₂AS annealed at 600 and 1100°C was investigated by means of isothermal calorimeter. An increase in the temperature of hydration brought about initial acceleration of all samples, as indicated by the increased magnitude of peak of calorimetric curves. The microstructure of the samples cured at hydrothermal condition after 1 and 7 days has been examined by means of scanning electron microscopy (SEM). Fine crystals of calcium silicate hydrate (C–S–H) were developed in C₂S samples, while C₂AS has been hydrated to form gehlenite hydrate supplemented by C–S–H.     

Cobalt-catalyzed C–N,C–O,C–S bond formation: synthesis of heterocycles

In recent decades, a large number of reports related to the synthesis of N-, O- and S-containing heterocycles have appeared owing to a wide variety of their biological activity. Traditional approaches require expensive or highly specialized equipment or would be of limited use to the synthetic organic chemist due to their highly inconvenient approaches. New strategies have been developed for the preparation of heterocycles in the last decades. Metal and non-metal catalysts are used in organic reactions with high activity. These synthetic strategies are becoming important and highly rewarding protocols in organic synthesis. In this review article, the synthesis of heterocycles is presented with the application of cobalt metal as a catalyst. It describes the formation of different sized heterocyclic rings containing different heteroatoms.

     

Pimprinols A–C,from the terrestrial actinomycete,Streptomyces sp.

A Streptomyces sp. Lv3-13, isolated from the rhizosphere soil of the plant Mespilus germanica, has yielded three new pimprinine derivatives, named pimprinols A–C (1–3) and the unknown (2-aminophenyl)(2-ethyloxazol-5-yl) methanone (4) along with the known compounds 2-ethyl oxazole pimprinine and 2-propyl oxazole pimprinine. The structures of the compounds were elucidated based on spectroscopic methods including UV, HR-ESIMS and 1D, 2D NMR data. Compounds 1–4 were screened for antimicrobial and cytotoxic activities.     

Transition-Metal-Free C(sp2)–C(sp2) Cross-Coupling of Diazo Quinones with Catechol Boronic Esters

A transition-metal-free C(sp²)−C(sp²) bond formation reaction by the cross-coupling of diazo quinones with catechol boronic esters was developed. With this protocol, a variety of biaryls and alkenyl phenols were obtained in good to high yields under mild conditions. The reaction tolerates various functionalities and is applicable to the derivatization of pharmaceuticals and natural products. The synthetic utility of the method was demonstrated by the short synthesis of multi-substituted triphenylenes and three bioactive natural products, honokiol, moracin M, and stemofuran A. Mechanistic studies and density functional theory (DFT) calculations revealed that the reaction involves attack of the boronic ester by a singlet quinone carbene followed by a 1,2-rearrangement through a stepwise mechanism.     

Regioselective C–S bond formation accomplished by copper-catalyzed regioselective C–F substitution of perfluoroarenes with aryl thioacetates or benzyl thioacetate

Practical and straightforward method for regioselective C–S bond formation accomplished by copper-catalyzed regioselective C–F substitution of electron-deficient perfluoroarenes with aryl thioacetates or benzyl thioacetate has been developed. Because of its high reaction efficiency, good chemoselectivity and regioselectivity, and excellent functional-group compatibility, this protocol provides a useful and operationally simple access to polyfluoroaryl thioethers used for drugs and material chemistry.     

Sulfonylation of C(sp3)–H bond for synthesis of 2-sulfolmethyl azaarenes catalyzed by TBAI in water

Research on Chemical Intermediates - A tetrabutylammonium iodide (TBAI)-catalyzed method for synthesis of 2-sulfolmethyl quinolone has been developed. Using water as solvent, a wide range of...     

Efficient Synthesis of Phenoxathiines via the Cascade C–H Hydroxylation–C–S Coupling–C–O Cyclization Reaction

Russian Journal of General Chemistry - The ligand-free and simple cascade C–H hydroxylation–C–S coupling–C–O cyclization reaction has been used as the synthetic...