[Study on preparation method of reference substance of aristolactam â -deoxyriboside adducts].

A two-step synthetic process of bromination and cross-coupling with aristololactam Ⅰ as raw material was successfully developed. Three aristolactam Ⅰ-deoxyriboside adducts, namely AAⅠ-dA, AAⅠ-dG, and AAⅠ-dC were obtained after a sequential procedure of impurity removal and purification in four different solvents. The yield of the two-step reaction can reach 90%, and the purity of the product is more than 98%, which can meet the requirements of qualitative and quantitative analyses as traditional Chinese medicine chemical reference products. The process has been proven to have good repeatability and scalability, and it features a concise preparation procedure, efficient purification, and high yield and purity, requiring no chromatographic separation. Compared with pre-vious methods, the newly developed process has significant advantages and is suitable for the preparation of chemical reference products of aristolactam Ⅰ-deoxyriboside adducts. This process provides technical support for the preparation of reference products of aristolactam Ⅰ-deoxyriboside adducts and a solid material basis for the related toxicological research.

Chromosome-level assembly of the Neolamarckia cadamba genome provides insights into the evolution of cadambine biosynthesis.

Neolamarckia cadamba (Roxb.), a close relative of Coffea canephora and Ophiorrhiza pumila, is an important traditional medicine in Southeast Asia. Three major glycosidic monoterpenoid indole alkaloids (MIAs), cadambine and its derivatives 3ß-isodihydrocadambine and 3ß-dihydrocadambine, accumulate in the bark and leaves, and exhibit antimalarial, antiproliferative, antioxidant, anticancer and anti-inflammatory activities. Here, we report a chromosome-scale N. cadamba genome, with 744.5 Mb assembled into 22 pseudochromosomes with contig N50 and scaffold N50 of 824.14 Kb and 29.20 Mb, respectively. Comparative genomic analysis of N. cadamba with Co. canephora revealed that N. cadamba underwent a relatively recent whole-genome duplication (WGD) event after diverging from Co. canephora, which contributed to the evolution of the MIA biosynthetic pathway. We determined the key intermediates of the cadambine biosynthetic pathway and further showed that NcSTR1 catalyzed the synthesis of strictosidine in N. cadamba. A new component, epoxystrictosidine (C27H34N2O10, m/z 547.2285), was identified in the cadambine biosynthetic pathway. Combining genome-wide association study (GWAS), population analysis, multi-omics analysis and metabolic gene cluster prediction, this study will shed light on the evolution of MIA biosynthetic pathway genes. This N. cadamba reference sequence will accelerate the understanding of the evolutionary history of specific metabolic pathways and facilitate the development of tools for enhancing bioactive productivity by metabolic engineering in microbes or by molecular breeding in plants.

Antibacterial Mechanism of Shikonin Against Vibrio vulnificus and Its Healing Potential on Infected Mice with Full-Thickness Excised Skin.

Shikonin has anticancer, anti-inflammatory, and wound healing activities. Vibrio vulnificus is an important marine foodborne pathogen with a high fatality rate and rapid pathogenesis that can infect humans through ingestion and wounds. In this study, the antibacterial activity and possible antibacterial mechanism of shikonin against V. vulnificus were investigated. In addition, the ability of shikonin to control V. vulnificus infection in both pathways was assessed by artificially contaminated oysters and full-thickness excised skin-infected mice. Shikonin treatment can cause abnormal cell membrane function, as evidenced by hyperpolarization of the cell membrane, significant decreased intracellular ATP concentration (p < 0.05), significant increased intracellular reactive oxygen species and malondialdehyde content (p < 0.05), decreased cell membrane integrity, and changes in cell morphology. Shikonin at 40 and 80 µg/mL reduced bacterial numbers in shikonin-contaminated oysters by 3.58 and 2.18 log colony-forming unit (CFU)/mL. Shikonin can promote wound healing in mice infected with V. vulnificus by promoting the formation of granulation tissue, hair follicles, and sebaceous glands, promoting epithelial cell regeneration and epidermal growth factor production. These findings suggest that shikonin has a strong inactivation effect on V. vulnificus and can be used in food production and wound healing to effectively control V. vulnificus and reduce the number of diseases associated with it.

A chromatography-free and aqueous waste-free process for thioamide preparation with Lawesson's reagent.

After completing the thio-substitution with Lawesson's reagent, ethanol was found to be effective in the decomposition of the inherent stoichiometric six-membered-ring byproduct from the Lawesson's reagent to a highly polarized diethyl thiophosphonate. The treatment significantly simplified the following chromatography purification of the desired thioamide in a small scale preparation. As scaling up the preparation of two pincer-type thioamides, we have successfully developed a convenient process with ethylene glycol to replace ethanol during the workup, including a traditional phase separation, extraction, and recrystallization. The newly developed chromatography-free procedure did not generate P-containing aqueous waste, and only organic effluents were discharged. It is believed that the optimized procedure offers the great opportunity of applying the Lawesson's reagent for various thio-substitution reactions on a large scale.

Tandem Synthesis of 2-Carboxybenzofurans via Sequential Cu-Catalyzed C-O Coupling and Mo(CO)6-Mediated Carbonylation Reactions.

A modular tandem synthesis of 2-carboxybenzofurans from 2-gem-dibromovinylphenols has been established based on a sequence of Cu-catalyzed intramolecular C-O coupling and Mo(CO)6-mediated intermolecular carbonylation reactions. This protocol allowed one-step access to a broad variety of functionalized benzofuran-2-carboxylic acids, esters, and amides in good to excellent yields under Pd- and CO gas-free conditions.

Highly Linear Polyethylenes Achieved Using Thermo-Stable and Efficient Cobalt Precatalysts Bearing Carbocyclic-Fused NNN-Pincer Ligand.

Six examples of 2-(1-arylimino)ethyl-9-arylimino-5,6,7,8-tetrahydrocycloheptapyridine-cobalt(II) chloride complexes, [2-(1-ArN)C2H3-9-ArN-5,6,7,8-C5H8C5H3N]CoCl2, (Ar = 2-(C5H9)-6-MeC6H3 Co1, 2-(C6H11)-6-MeC6H3 Co2, 2-(C8H15)-6-MeC6H3 Co3, 2-(C5H9)-4,6-Me2C6H2 Co4, 2-(C6H11)-4,6-Me2C6H2 Co5, and 2-(C8H15)-4,6-Me2C6H2 Co6), were synthesized by the direct reaction of the corresponding ortho-cycloalkyl substituted carbocyclic-fused bis(arylimino)pyridines (L1⁻L6) and cobalt(II) chloride in ethanol with good yields. All the synthesized ligands (L1⁻L6) and their corresponding cobalt complexes (Co1⁻Co6) were fully characterized by FT-IR, ¹H/13C-NMR spectroscopy and elemental analysis. The crystal structure of Co2 and Co3 revealed that the ring puckering of both the ortho-cyclohexyl/cyclooctyl substituents and the one pyridine-fused seven-membered ring; a square-based pyramidal geometry is conferred around the metal center. On treatment with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the six complexes showed high activities (up to 4.09 × 106 g of PE mol-1 (Co) h-1) toward ethylene polymerization at temperatures between 20 °C and 70 °C with the catalytic activities correlating with the type of ortho-cycloalkyl substituent: Cyclopentyl (Co1 and Co4) > cyclohexyl (Co2 and Co5) > cyclooctyl (Co3 and Co6) for either R = H or Me and afforded strictly linear polyethylene (Tm > 130 °C). The narrow unimodal distributions of the resulting polymers are consistent with single-site active species for the precatalyst. Furthermore, compared to the previously reported cobalt analogues, the titled precatalysts exhibited good thermo-stability (up to 70 °C) and possessed longer lifetime along with a higher molecular weight of PE (Mw: 9.2~25.3 kg mol-1).

[Chemical constituents from hypoglycemic active part of Plantaginis Semen].

The chemical constituents of Plantaginis Semen with hypoglycemic effect was investigated in this paper. The previous results of the in vivo hypoglycemic effect showed that 60% ethanol extract of Plantaginis Semen decreased the levels of FBG and improved the glucose tolerance in high fat diet(HFD)-induced diabetic C57BL/6 mice. Then, in the present study, the above potential bioactive extract was separated and purified by silica gel, ODS, Sephadex LH-20 column chromatography, medium pressure liquid chromatography(MPLC)and preparative HPLC. The structures of isolated compounds were identified by physicochemical properties and spectral analyses. Eight compounds were obtained and identified as 4, 4a, 5, 7a-tetrahydro-7-(hydroxymethyl)cyclopenta[c]pyran-3(1H)-one(1), iridolactone(2), pedicularislacton(3), rehmaglutin C(4), geniposidic acid(5), p-hydroxylphenylglycerol(6), 1, 2-benzenediol-4-(2-hydroxyethyl)(7), and 3-buten-2-one-4-[3-(ß-D-glucopyranosyloxy)-4-hydroxyphenyl](8). Among them, compounds 1-5 were iridoids, and 6-8 were phenolic acids. Compound 1 was a new natural product, and compounds 2-4, 6 and 8 were isolated from the Plantaginaceae family for the first time.

An efficient Pd-NHC catalyst system in situ generated from Na2PdCl4 and PEG-functionalized imidazolium salts for Mizoroki-Heck reactions in water.

Three PEG-functionalized imidazolium salts L1-L3 were designed and prepared from commercially available materials via a simple method. Their corresponding water soluble Pd-NHC catalysts, in situ generated from the imidazolium salts L1-L3 and Na2PdCl4 in water, showed impressive catalytic activity for aqueous Mizoroki-Heck reactions. The kinetic study revealed that the Pd catalyst derived from the imidazolium salt L1, bearing a pyridine-2-methyl substituent at the N3 atom of the imidazole ring, showed the best catalytic activity. Under the optimal conditions, a wide range of substituted alkenes were achieved in good to excellent yields from various aryl bromides and alkenes with the catalyst TON of up to 10,000.

Highly bulky and stable geometry-constrained iminopyridines: Synthesis, structure and application in Pd-catalyzed Suzuki coupling of aryl chlorides.

A series of bulky geometry-constrained iminopyridylpalladium chlorides were developed. The steric environment adjacent to the nitrogen atom in the pyridine rings and diimine parts enhanced the thermal stability of the palladium species. Bulkier groups at the imino group stabilized the palladium species and the corresponding palladium chlorides showed high activities in the coupling reaction of aryl chlorides.

Recent Advances in Dynamic Kinetic Resolution by Chiral Bifunctional (Thio)urea- and Squaramide-Based Organocatalysts.

The organocatalysis-based dynamic kinetic resolution (DKR) process has proved to be a powerful strategy for the construction of chiral compounds. In this feature review, we summarized recent progress on the DKR process, which was promoted by chiral bifunctional (thio)urea and squaramide catalysis via hydrogen-bonding interactions between substrates and catalysts. A wide range of asymmetric reactions involving DKR, such as asymmetric alcoholysis of azlactones, asymmetric Michael-Michael cascade reaction, and enantioselective selenocyclization, are reviewed and demonstrate the efficiency of this strategy. The (thio)urea and squaramide catalysts with dual activation would be efficient for more unmet challenges in dynamic kinetic resolution.

Copper-catalyzed oxidative alkenylation of thioethers via Csp(3)-H functionalization.

A novel copper-catalyzed oxidative alkenylation of thioethers via Csp(3)-H functionalization to construct allylic thioethers is first demonstrated. Different 1,1-disubstituted olefins could cross-couple with thioethers to generate the corresponding alkenylation products in moderate to excellent yields. This reaction is supposed to proceed via a radical process.

A mild copper-catalyzed aerobic oxidative thiocyanation of arylboronic acids with TMSNCS.

A facile and efficient transformation of arylboronic acids to their corresponding aryl thiocyanates has been successfully developed. Based on the CuCl-catalyzed oxidative cross-coupling reaction between arylboronic acids and trimethylsilylisothiocyanate (TMSNCS) under oxygen atmosphere, the transformation can be readily conducted at ambient temperature. The newly-developed protocol provided a competitive synthetic approach to aryl thiocyanates that can tolerate a broad range of reactive functional groups and/or strong electron-withdrawing groups.

Response of WUE of maize at ear stage to the coupling effect of CO2 and temperature.

In the face of global warming, the photosynthesis and transpiration of plants will change greatly, which will ultimately affect the water use efficiency (WUE) of plants. In order to study the coupling effects of CO2 and temperature on WUE of maize at ear stage, 'Zhengdan 958' was taken as the research object, and 5 temperatures (20 °C, 25 °C, 30 °C, 35 °C and 40 °C) and 11 CO2 concentration (400, 300, 200, 150, 100, 50, 400, 400, 600, 800 and 1000 µmol mol-1) were set to measure the parameters such as net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and intercellular CO2 concentration (Ci) of single leaves. The response of WUE (Pn/Tr) to CO2 and temperature was evaluated by a CO2 response model. The results show that at the same temperature, Pn and WUE increased with CO2 level, while Tr decreased as CO2 level increases; at the same CO2 concentration, Pn and Tr were both positively correlated with temperature, while WUE decreased with the increase of temperature. The maximum value of WUE was obtained when the CO2 concentration was 1000 µmol mol-1 and the temperature was 20.0 °C. The results suggest that global warming will not improve WUE of maize, which will bring more severe challenges to water-saving agriculture and food security.

Protocol to study the photosynthetic response of maize to the CO2-temperature coupling effect at ear stage using a specialized designed gradient.

Global warming will change the photosynthesis and transpiration of plants greatly and ultimately affect water use efficiency (WUE). Here, we present a protocol to investigate the response of maize WUE to the coupling effect of CO2 and temperature at ear stage using a specialized designed gradient. We describe steps for plant culture, parameter measurements, model fitting, and statistical analysis. This protocol holds potential for studying the response of WUE and CO2 adaptation across various plant species. For complete details on the use and execution of this protocol, please refer to Sun et al.1.

Pd(II)-Catalyzed enantioselective C-H olefination toward the synthesis of P-stereogenic phosphinamides.

P-Stereogenic phosphorus compounds are important structural elements in chiral ligands or organocatalysts. Herein, we report a Pd(II)-catalyzed enantioselective C-H olefination toward the synthesis of P-stereogenic phosphinamides using cheap commercially available L-pGlu-OH as a chiral ligand. A broad range of P-stereogenic phosphinamides were gained in good yields with high enantioselectivities (33 examples, up to 77% yield, 99% ee) via desymmetrization and kinetic resolution.

Revealing the mechanism of citral induced entry of Vibrio vulnificus into viable but not culturable (VBNC) state based on transcriptomics.

Citral has attracted much attention as a safe and effective plant-derived bacteriostatic agent. However, the ability of citral to induce the formation of VBNC state in Vibrio vulnificus has not been evaluated. In the present study, V. vulnificus was shown to be induced to form the VBNC state at 4.5 h and 3 h of citral treatment at 4MIC and 6MIC. Moreover, the citral-induced VBNC state of V. vulnificus maintained some respiratory chain activity and was able to recover well in both APW media, APW media supplemented with 5 % (v/v) Tween 80 and 2 mg/mL sodium pyruvate. Field emission and transmission electron microscopy showed that the external structure of the citral-induced VBNC V. vulnificus cells was shortened to short rods, with folded cell membrane, rough cell surface, and dense cytoplasm and loose nuclear material in the internal cell structure. In addition, the possible molecular mechanisms of citral-induced formation and recovery of V. vulnificus in the VBNC state were explored by transcriptomics. Transcriptome analyses revealed that 1118 genes were significantly altered upon entry into the VBNC state, and 1052 genes were changed after resuscitation. Most of the physiological activities related to energy production were inhibited in the citral-induced VBNC state of V. vulnificus; however, the bacteria retained its pathogenicity. The citral-induced resuscitation of V. vulnificus in the VBNC state selectively restored the activity of some genes related to bacterial growth and reproduction. Meanwhile, the expression levels of other genes may have been influenced by citral-induced resuscitation after the formation of the VBNC state. In conclusion, this study evaluated and analyzed the ability and possible mechanism of citral on the formation of VBNC state and the recovery of VBNC state of V. vulnificus, and made a comprehensive assessment for the safety of citral application in food production.

Hexachlorocyclotriphosphazene (HCCP)-mediated direct formation of thioethers and ethers from quinazolin-4(3H)-ones.

A hexachlorocyclotriphosphazene (HCCP)-mediated direct formation of quinazoline (thio)ethers from quinazolin-4(3H)-ones has been developed. Treatment of quinazolin-4(3H)-ones with HCCP, diisopropylethylamine (DIPEA), and thiophenols resulted in formation of the corresponding 4-arylthioquinazoline derivatives in moderate to excellent yields. This method has also been utilized to prepare 4-aryloxyquinazoline and 4-alkoxyquinazoline derivatives using phenols and sodium alkoxides as the nucleophiles.

Synthesis of P-Stereogenic Phosphinamides via Pd(II)-Catalyzed Enantioselective C-H Alkynylation.

P-Stereogenic phosphinamides represent important structural elements in chiral organocatalysts and bioactive compounds. Herein, we report Pd(II)-catalyzed enantioselective C-H alkynylation using cheap commercially available l-pyroglutamic acid as a chiral ligand. A range of structurally diverse P-stereogenic phosphinamides was prepared in good yields with high enantioselectivities via desymmetrization and kinetic resolution. A tailor-made congested directing group, N-ethyl-N-(3-methylpyridin-2-yl)amino, was crucial for the reactivity.

A general and facile one-pot process of isothiocyanates from amines under aqueous conditions.

A general and facile one-pot protocol for the preparation of a broad range of alkyl and aryl isothiocyanates has been developed from their corresponding primary amines under aqueous conditions. This synthetic process involves an in situ generation of a dithiocarbamate salt from the amine substrate by reacting with CS(2) followed by elimination to form the isothiocyanate product with cyanuric acid as the desulfurylation reagent. The choice of solvent is of decisive importance for the successful formation of the dithiocarbamate salt particularly for highly electron-deficient substrates. This novel and economical method is suitable for scale-up activities.

Ni-catalyzed reductive decyanation of nitriles with ethanol as the reductant.

A nickel-catalyzed reductive decyanation of aromatic nitriles has been developed, in which the readily available and abundant ethanol was applied as the hydride donor. Various functional groups on the aromatic rings, such as alkoxyl, amino, imino and amide, were compatible in this catalytic protocol. Heteroaryl, benzylic and alkenyl nitriles were also tolerated. Mechanistic investigation indicated that ethanol provided hydride efficiently via ß-hydride elimination in this reductive decyanation.