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Herein we report the first enantioselective total synthesis of 3,5-dimethylorsellinic acid-derived meroterpenoids (-)-berkeleyone A and its five congeners ((-)-preaustinoids A, A1, B, B1, and B2) in 12-15 steps, starting from commercially available 2,4,6-trihydroxybenzoic acid hydrate. Based upon the recognition of latent symmetry within D-ring, our convergent synthesis features two critical reactions: 1) a symmetry-breaking, diastereoselective dearomative alkylation to assemble the entire carbon core, and 2) a Sc(OTf)3 -mediated sequential Krapcho dealkoxycarbonylation/carbonyl α-tert-alkylation to forge the intricate bicyclo[3.3.1]nonane framework. We also conducted our preliminary biomimetic investigations and uncovered a series of rearrangements (α-ketol, α-hydroxyl-β-diketone, etc.) responsible for the biomimetic diversification of (-)-berkeleyone A into its five preaustinoid congeners.

Fsa2 and Phm7 are a unique pair of pericyclases catalyzing [4 + 2] cycloaddition reactions with reverse stereoselectivities in the biosynthesis of equisetin and phomasetin, both of which are potent HIV-1 integrase inhibitors. We here solve the crystal structures of Fsa2 and Phm7, both of which possess unusual "two-β barrel" folds. Different residues are evident between the active sites of Fsa2 and Phm7, and modeling experiments provide key structural information determining the reverse stereoselectivities. These results provide a better understanding of how natural pericyclases control the catalytic stereoselectivities and benefit the protein engineering in future.

LC-MS-oriented fractionation of the sponge Aaptos suberitoides resulted in the isolation of four heptacyclic alkaloids, aaptodines A-D (1-4), which contain 9,10-dihydrofuro[2,3-f][1,3]oxazolo[5,4-h]quinolone and 7,8-dihydrocyclopenta[de][1,6]naphthyridine subunits with a spiro carbon atom. The structures were determined on the basis of NMR spectroscopic and single-crystal X-ray diffraction data analysis aided by electronic circular dichroism calculations and Mosher's method. A biosynthetic pathway for the formation of aaptodines A-D is postulated. Aaptodine D exhibits potent inhibition against osteoclast formation.

Variable Angle Tow placement is a way to steer individual curvilinear fibers. This work presents the assessment of tensile behavior of open-hole composite laminates with Variable Angle Tow reinforcement. A new multi-scale finite element method, consisting of a microscale unit cell model and a macroscale gradient property model, is developed to simulate Variable Angle Tow structures with various fiber trajectories. The tensile strength and the failure process of open-hole reinforced laminates with Variable Angle Tow reinforcement under tensile loading are predicted and analyzed. Experiments are also conducted to investigate reinforcing efficiency and failure modes of the open-hole laminates. The comparison of predicted and experimental results for the tensile strength and failure modes of T700/Epoxy laminates demonstrates clearly that the mechanical behavior of Variable Angle Tow structure can be simulated very well by the proposed multi-scale model. Moreover, it is found that the tensile strength of Variable Angle Tow laminates is closely related to the eccentricity and it reaches the maximum value only when the trajectories of curvilinear fibers keeps consistent with maximum principal stress trajectories of the open-hole plate.

In present study, laminates with the type of [±θ°]S and [0°2/±θ°]S are investigated in order to clearly show the effect of material shear nonlinearity, and then theoretical predictions are compared with experimental data. In the whole process of generating failure envelopes, secant shear modulus instead of initial shear modulus is used for accurate shear stress-strain relation. The modulus values are recalculated every time when the combining load is changed. Final failure envelopes are then compared between numerical models. It is found that the variation in the size of safe regions from nonlinear analysis is closely related to the way of combing load and fiber directions. So in the process of improving failure theories or in the applications of failure theories, the effect of material nonlinearity can be considered appropriately.

Bioassay-guided fractionation in association with LC-MS and NMR detection led to the isolation of six new alkaloids, sclerotiamides C-H (

Capitalizing on the late-stage diversification of an essential 1,3-diene intermediate, we describe herein a 9-step enantioselective total synthesis of (+)-hyperforin and (+)-pyrohyperforin, starting from commercially available allylacetone. Our convergent synthesis features a series of critical reactions: 1) an enantioselective deconjugative α-alkylation of α,β-unsaturated acid using chiral lithium amides as noncovalent stereodirecting auxiliaries; 2) a HfCl

Pimarane-type diterpenoids are widely distributed in all domains of life, but no structures or catalytic mechanisms of pimarane-type diterpene synthases (DTSs) have been characterized. Here, we report that two class I DTSs, Sat1646 and Stt4548, each accept copalyl diphosphate (CPP) as the substrate to produce isopimara-8,15-diene (1). Sat1646 can also accept syn-CPP and produce syn-isopimaradiene/pimaradiene analogues (2–7), among which 2 possesses a previously unreported "6/6/7" ring skeleton. We solve the crystal structures of Sat1646, Sat1646 complexed with magnesium ions, and Stt4548, thereby revealing the active sites of these pimarane-type DTSs. Substrate modeling and subsequent site-directed mutagenesis experiments demonstrate different structural bases of Sat1646 and Stt4548 for 1 production. Comparisons with previously reported DTSs reveal their distinct carbocation intermediate stabilization mechanisms, which control the conversion of a single substrate CPP into structurally diverse diterpene products. These results illustrate the structural bases for enzymatic catalyses of pimarane-type DTSs, potentially facilitating future DTS engineering and combinatorial biosynthesis. Pimaranes are diterpenoid natural products with poorly characterised biosynthetic pathways. Here pimaranetype diterpenoid synthases are functionally and structurally characterised and shown to exploit distinct modes of intermediate stabilisation.

Influence of material shear nonlinearity on multidirectional laminates in terms of failure envelopes was investigated. In applying classic laminate theory, elastic constants were employed in transverse and longitudinal directions, while initial shear modulus was substituted by the secant shear modulus, which was achieved by means of Ramberg-Osgood model. The fracture curves were generated from maximum stress, Tsai-Wu and Puck criteria. The similarities and differences between nonlinear and linear shear models can be expressed in terms of symmetric balanced laminates [±θ°]2s and asymmetric laminates [0°2/±θ°], which are both arranged by material E-glass/MY750 oriented at different directions. All σ1 - σ2 failure envelopes due to material nonlinearity extend outward in tensile and compressive directions, but the phenomenon is not obvious with increasing ply angles. Similarly, the differences of all σ1 - τ12 failure envelopes between nonlinear shear analysis and linear shear analysis are decreasing with increased ply angles. Ply orientations and loading directions are involved in the effect of nonlinear shear properties on failure envelopes. According to the failure modes obtained from maximum stress criterion, it is reasonably derived that the influence of material shear nonlinearity will lead whether the failure envelopes from the other two failure criteria are more conservative or not.

LC-MS-oriented fractionation of the sponge

We propose a spectral collocation method based on the Chebyshev–Gauss–Lobatto points for linear Volterra integro-differential equations with vanishing delays. We derive an [math] - [math] version a-priori error estimate in the [math] -norm that is completely explicit in the local time steps and the local polynomial degrees. Numerical experiments are provided to confirm the theoretical results.

In this paper, the complex (DFT) modulated filter banks is described. Based on the research evidences and findings collected, it mainly focuses on 4 parts: the detailed history of complex (DFT) modulated filter banks part, complex (DFT) modulated filter banks, Matlab programs implementation part and the part of applications in details generally. In order to explain the impact of these aspects on the complex (DFT) modulated filter banks, evidence based on experts’ opinions and identification of facts was used.

In this study, a nickel coated carbon fiber (Ni-CF) tow is used to enable glass fiber reinforced plastics (GFRPs) to exhibit multi-functional properties with self-diagnosing function. The experimental results indicate that the Ni-CF exhibits desirable interfacial compatibility with the matrix resin and has no negative effect on the performance of GFRPs, thereby the loading conditions can be effectively monitored without deterioration. The electro-mechanical response suggests that the changes in resistance can be further divided into two stages corresponding to the two different safety states based on the strain under uniaxial tensile loading. At the same time, the composites were examined under cyclic loading conditions to confirm the stability and robustness of the Ni-CF as a sensing element. Moreover, the safety factor and reliability of composites were calculated based on the stress corresponding to the transition point of the safety states and the ultimate stress of the composites. Consequently, the results show that the reliability is close to 100% when the maximum safety factor of Ni-CF/GFRP is 1.5. In addition, we also suggest two different solutions for manufacturing self-diagnosing composites which can be individually applied in the development of the structures with low failure risk or with high safety requirements.

The stable soil carbon (C) pool in coastal wetlands, referred to as “blue C”, which has been extensively damaged by climate change and soil degradation, is of importance to maintain global C cycle. Therefore, to investigate the dynamic characteristics of soil respiration rate and evaluate C budgets in coastal wetlands are urgently. In this study, the diurnal and seasonal variation of soil respiration rate in the reed wetland land (RL) and the bare wetland land (BL) was measured in situ with the dynamic gas-infrared CO2 method in four seasons, and the factors impacted on the dynamic characteristics of soil respiration were investigated. The results showed that the diurnal variation of soil respiration rate consistently presented a “U” curve pattern in April, July, and September, with the maximum values at 12:00 a.m. and the minimum values at 6:00 a.m. In the same season, the diurnal soil respiration rate in RL was significantly greater than those in BL (P

The fungal cyclohexadepsipeptides destruxins (DTXs), isaridins (ISDs), and isariins (ISRs) are nonribosomal peptides whose structures include a 19-membered ring composed of five amino acid residues and one α- or β-hydroxy acid residue. These cyclohexadepsipeptides contain unusual nonproteinogenic amino acid–building blocks and possess a range of antiviral, antibacterial, and other activities. The biosynthetic gene clusters for ISDs and ISRs have not been identified, and the biosynthesis of the nonproteinogenic (3S)-methyl-l-proline residue, which is found in DTXs, ISDs, and many other natural products, lacks full characterization. In an ongoing effort to identify compounds that can inhibit the Zika virus (ZIKV), we examined the extract of marine-derived fungus Beauveria felina SX-6-22 and discovered 30 DTXs, ISDs, and ISRs (1–30) including seven new compounds (1–7). The anti-ZIKV assays showed that 9–12 and 16–18 possess inhibitory activities against ZIKV RNA replication and NS5 (nonstructural protein 5) production in ZIKV-infected A549 cells. We sequenced the genome of B. felina SX-6-22 and identified three biosynthetic gene clusters detx, isd and isr, which are responsible for the biosynthesis of DTXs, ISDs, and ISRs, respectively. Comparative analyses of the three gene clusters clarified the biosynthetic relationships among these cyclohexadepsipeptides. Finally, we characterized the entire biosynthesis of nonproteinogenic building block (3S)-methyl-l-proline. The Δ1-pyrroline-5-carboxylate reductases (P5CRs), also used in the biosynthesis of l-proline, were demonstrated to catalyze the final reduction step in (3S)-methyl-l-proline formation, suggesting potential cross talk between primary and secondary metabolisms. These results provide opportunities for biosynthetic pathway engineering to generate new anti-ZIKV cyclohexadepsipeptides.

A redox-responsive hybrid of polyoxometalate and conducting oligomer including its self-assemblies with controllable morphologies are reported. To this end, a hybrid molecule, containing a Lindqvist hexamolybdate as the polar head group and N,N'-bis(4'-amino-2,6-dimethylphenyl)-1,4-quinonediimine as the redox-responsive and aggregating group, is prepared. This hybrid exhibits redox-responsive behavior with controllable assembling morphological transition from spherical vesicles to short cylindrical vesicles. Besides, the hybrid-based self-assemblies are transferred to the surface, thus the surface wettability can be well-tuned owing to the morphological transitions of the self-assemblies. By marrying conducting materials with polyoxometalate chemistry, this research opens a new horizon of polyoxometalate-based self-assembled systems with potential applications in functional materials.

Sub-nanoscaled polyalkoxyvanadates (PAOVs) functionalized with various aliphatic acids are evaluated for their insulin-sensitizing activity in lowering the blood glucose levels of diabetic mice in typical glucose tolerance tests. All the PAOVs can restore the blood glucose to normal levels after a single oral administration of PAOVs. Among them, the myristic acid-modified PAOVs enable the response of insulin to the repeated glucose challenges, lasting for up to 13 h. The combined administration of PAOVs exerts better glucose control over insulin alone, while the capric acid- and myristic acid-modified ones can enhance the responsiveness of insulin to glucose challenge and is comparable to a clinical-used derivative of insulin. Interestingly, continuous glucose monitoring shows that myristic acid-modified PAOV derivatives sensitize the responsiveness of insulin, almost matching with that of a healthy pancreas. These discoveries open up new opportunities for the application of PAOVs to promote glucose-responsive and long-lasting activity of insulin, which are expected to aid the accurate blood glucose control in insulin therapy while reducing the number of insulin administrations.

A 1:1 complex of Lanthanide-substituted Lindqvist-type oxo-nitrosyl polymolybdate [NBu4][La(CH3OH)2(DCU)NO3{Mo5O13(OMe)4(NO)}]·CH3OH (1) has been successfully synthesized by a one-pot self-assembly process of hydroxylamine hydrochloride with octamolybdate, DCC and La(NO3)3 in methanol under mild reaction conditions. The structure is determined by X-ray crystallography. It is notable that the compound is a Lindqvist-type POM with a capped lanthanum ion which is nine coordinated in a distorted square antiprism geometry. Interestingly, NO3− as the precursor, as well as the hydrated product DCU of DCC, are both coordinated with Lanthanum ion. The structure has also been characterized by IR, UV–vis and photoluminescence analysis. Photoluminescence analysis reveals that compound 1 emits weak green light in CH3CN, with the maximum emission at 530 nm.

Two novel Diels-Alder [4 + 2] cycloadducts of quaternary protoberberine alkaloids and fumaric acid monoanion, corydecumbenines A and B (1 and 2), and six known isoquinoline analogues (3–8) were isolated from the rhizomes of Corydalis decumbens. The planar structures of 1 and 2 were elucidated by extensive spectroscopic analysis including UV, IR, HRESIMS, 1D and 2D NMR. Chiral chromatography of 1 and 2 afforded two pairs of enantiomers (+)-corydecumbenine A (1a), (–)-corydecumbenine A (1b), (+)-corydecumbenine B (2a), and (–)-corydecumbenine B (2b), respectively, and their absolute configurations were determined by single-crystal X-ray crystallography and comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Compounds 1b and 2b exhibited significant nitric oxide (NO) inhibitory activities in lipopolysaccharide (LPS)-stimulated BV-2 cells with IC50 values of 11.6 and 16.2 μM, respectively, comparable to the positive control indomethacin (IC50 = 10.3 μM), and they could also decrease the level of interleukin (IL)-1β in BV-2 cells in a dose-dependent manner. Most of the isolates showed neuroprotective effects against the injury of OGD/R-induced PC12 cells at 20 μM.

A water-soluble single-sided tris-functionalized Anderson-type polyoxometalate (POM) with counter ammonium cations, (NH4)2{[NH3C(CH2O)3]Cr(OH)3Mo6O18}·5H2O(1), has been synthesized by a hydrothermal reaction of parent Anderson-type POMs, [NH4]3[Cr(OH)6Mo6O18] (CrMo6) and tris ligand (HOCH2)3CNH2·HCl (Tris) in aqueous solution. Single-crystal X-ray diffraction analysis has revealed that compound 1 crystallizes in triclinic space group P-1. Each asymmetric unit contains one protonated single-side tris-functionalized Anderson-type POMs anion cluster, {[NH3C(CH2O)3]Cr(OH)3Mo6O18}2- (CrMo6-tris-NH3), and two NH4+ counter cations and five crystallized H2O solvent molecules, which can assemble into a layer-by-layer structure via hydrogen bonding interactions. Furthermore, compound 1 was characterized by elemental analysis, FT-IR, 1H NMR, UV–Vis and TGA. Such a water-soluble tris-functionalized POM with the remote amino reactive group has not been reported before and it may serve as a valuable synthon for further post-functionalization in aqueous solution.

Correction for ‘Diversified polyoxovanadate derivatives obtained by copper(i)-catalysed azide–alkyne cycloaddition reaction: their synthesis and structural characterization’ by Hongli Jia et al., Dalton Trans., 2018, 47, 577–584.

The system idea was used to comprehensively evaluate the equipment management information system construction, and the implementation effect of the equipment management information system was objectively reflected, thus a scientific basis for system decision-making was provided. Firstly, the index system of the military equipment management information system was established. On the basis of this, the entropy weight method and the AHP model were combined to evaluate the equipment management information system, and finally, the comprehensive level of the equipment management information system is obtained. The results show that the evaluation of the equipment management information system based on the entropy weight method and the AHP model can effectively test the equipment management information system capability of a certain type of force and provide guidance and reference for further decision-making.

In this work, we confirmed that the copper-catalysed azide-alkyne cycloaddition (CuAAC) reaction is an effective method for the organic-functionalization of polyoxometalates (POMs). Herein, for the first time, four novel 1,2,3-triazole functionalized polyoxovanadate (POV) organic-inorganic hybrids, (Bu