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In this work, pyrrole-2-carboxamides were designed with a structure-guided strategy based on the crystal structure of MmpL3 and a pharmacophore model. The structure-activity relationship studies revealed that attaching phenyl and pyridyl groups with electron-withdrawing substituents to the pyrrole ring and attaching bulky substituents to the carboxamide greatly improved anti-TB activity. Most compounds showed potent anti-TB activity (MIC0.016 μg/mL) and low cytotoxicity (IC

A series of alkynyl-containing maleimides with potent anti-tuberculosis (TB) activity was developed through a rigid group substitution strategy based on our previous study. Systematic optimization of the two side chains flanking the maleimide core led to new compounds with potent activity against Mycobacterium tuberculosis (MIC 1 μg/mL) and low cytotoxicity (IC

A convenient, rapid H2SO4-promoted regioselective monobromination reaction with N-bromosuccinimide was developed. The desired para-monobrominated or ortho-monobrominated products of phenol derivati...

A highly efficient and convenient protocol was developed to access 2-amino-4H-benzothiopyran-4-ones through a process of conjugated addition–elimination. The sulfinyl group was proved to be the optimum leaving group by thorough investigations on the elimination of sulfide, sulfinyl, and sulfonyl groups at the 2-position of benzothiopyranone. Most 2-aminobenzothiopyranones were obtained in good to excellent yields under refluxing in isopropanol within 36 h. This method is base-free and the substrate scope in terms of electronic properties of the substituents of the benzothiopyranone is broad. The ten grams scale-up synthesis of the representative compounds 4a and 4d was implemented to show the practical application of this reaction, which afforded the corresponding compounds in good yields and excellent chemical purity without requiring column chromatographical purification.

In this study, three novel series of benzoxazinone, benzothiopyranone and benzopyranone derivatives were designed through scaffold morphing from benzothiazinones to target DprE1. All compounds were evaluated for their in vitro activities against Mycobacterium tuberculosis and cytotoxicity against Vero cell line. Among these three series, the benzothiopyranone series displayed excellent antimycobacterial activity and low cytotoxicity. In particular, compound 6b exhibited potent in vitro activity against both drug-susceptible and drug-resistant tuberculosis clinical strains with MICs0.016 μg/mL. In addition, compound 6b demonstrated excellent ADME/T and PK properties and potent in vivo efficacy with bactericidal activity in an acute mouse model of tuberculosis. The antituberculosis effect of compound 6b is most likely attributed to its excellent anti-DprE1 activity. As such, compound 6b is under evaluation as a potential clinical candidate for treatment of tuberculosis. The current study provided new insight into the structural and pharmacological requirements for DprE1 inhibitors as potent antitubercular agents.

We reported three distinct series of novel benzothiopyranones, derived from an active metabolite (M-1) of anti-TB agent 6b. These small molecules were evaluated for their biological activities against a range of Mycobacterium tuberculosis (M. tuberculosis) strains. Preliminary druggability evaluation demonstrated that M-1 showed good aqueous solubility and hepatocyte stability. Benzothiopyranones with acyl, sulfonyl and phosphoryl groups exhibited potent in vitro inhibitory activity against M. tuberculosis H37Rv and low cytotoxicity. In particular, compound 3d, containing a benzoate fragment, displayed marked metabolic stability and potent in vitro activity against drug-resistant tuberculosis clinical strains. Further druggability evaluation based on the identified compounds 3d, 4e and 5b is ongoing for the discovery of promising anti-TB agents.

Yongle Atoll is a complex atoll composed of 13 separated small atolls/reefs in the Xisha Islands, northern-central South China Sea. Wide, deep channels connect the Yongle Atoll lagoon with the open ocean. The sea surface partial pressure of CO2 (pCO2) and sea–air CO2 flux was measured at different geomorphological locations on the atoll. Atmospheric pCO2 generally showed small diurnal variations, while seawater pCO2 showed large diurnal variations. Lingyang Reef lagoon, an atoll within Yongle Atoll, was used to check the spatial difference in seawater pCO2 and air–sea CO2 flux. The diurnal variation in seawater pCO2 was greater in the lagoon (258–748 μatm) than outside the lagoon area (354–476 μatm). Differences were also observed in the air–sea CO2 fluxes depending on geomorphological zone. The mean seawater pCO2 at Yongle Atoll is in the order of Lingyang Reef lagoon > inner reef slope of the Yongle Atoll > Yongle Atoll channel slope ≈ outer reef slope of the Yongle Atoll. The degree mixing between the lagoon and open sea through channels may have a key role in the horizontal distribution of seawater pCO2 in the Yongle Atoll. Additional analyses indicated that the daily variations in surface seawater pCO2 are significantly influenced by biological metabolic processes. The mean air–sea CO2 flux in the Yongle Atoll was ~ 3.2 mmol CO2 m−2 d−1, indicating that the Yongle Atoll acts as a net source of CO2 to the atmosphere.

A straightforward and one-pot synthesis of pyrrolo[3,4-c]pyrrole-1,3-diones via Ag(I)-catalyzed 1,3-dipolar cycloaddition of azomethine ylides with N-alkyl maleimide, followed by readily complete oxidation with DDQ, has been successfully developed. Further transformation with alkylamine/sodium alkoxide alcohol solution conveniently afforded novel polysubstituted pyrroles in good to excellent yields. This methodology for highly functionalized pyrroles performed well over a broad scope of substrates. It is conceivable that this efficient construction method for privileged pyrrole scaffolds could deliver more active compounds for medicinal chemistry research.

Various functionalized enantiomerically pure 3-hydroxymethyl-1,4-benzoxazine derivatives, including four stereoisomers, were synthesized from chiral 2,3-epoxy-4-trityloxybutanol. The synthesis was mild and metal-free. Yields of 52%–94%, and stereoselectivities of 95% to >99% ee, were obtained. The mechanism was investigated using online Fourier-transform infrared spectroscopy. This revealed a base-promoted cyclization to form tricycle-fused benzoxazinyl-oxazolidinone intermediates in situ, followed by a hydrolysis process. The method can be easily scaled and carried out in a one-pot manner. The usefulness of the obtained chiral 3-hydroxymethyl-1,4-benzoxazine derivatives as building blocks was showcased by further derivatization to form unique tricycle-fused benzoxazines.

The South China Sea (SCS) includes large areas of extensive coral reef development but its reefs are still poorly known. Yongle atoll is the biggest typical atoll in the Xisha Islands, central of SCS. Lingyang Reef is an isolated small atoll within the whole big Yongle atoll. A total of 144 and 119 coral species were recorded at big Yongle atoll and small Lingyang Reef, respectively. The real coral richness might be higher because species accumulation curve did not saturate. The coral diversity pattern was similar between big Yongle atoll and small Lingyang Reef. Coral communities fell into three clusters, consistent with their habitats on reef slope, reef flat and lagoon slope. The highest coral diversity was observed on reef slopes and the lowest coral diversity was found on lagoon slope. Genera richness was a better proxy for representing coral species diversity on both the big and small atoll but percent live coral cover was not a robust proxy on the small atoll, which only explained 24% of species diversity. This study demonstrated high coral diversity with consistent pattern along habitat types, as has been shown from many other reefs. While far from exhaustive, the study allows first glimpses on how much biodiversity is contained on SCS coral reefs, and hopes to give an impetus to their conservation. The study also suggests that simplified surveys at a small scale and the use of genera richness as an effective proxy for overall diversity can indeed provide important information to rapidly monitor and evaluate the coral diversity in remote locations.

A narrow size distribution of quantum dots (QDs) is needed for their application in photovoltaics but collection of such information is difficult. This paper demonstrates the application of Raman spectroscopy as a characterisation tool to extract the size distribution and crystalline fraction of Si QD samples fabricated through the sputter-anneal method. Measured Raman spectra of Si QD materials are de-convoluted into four components according to their origins and Raman scattering by Si QD cores is described by a modified one phonon confinement model, while other components are reproduced with Gaussian functions. Through fitting of Raman spectra, Si QD size distributions and Si crystalline fractions are obtained. The results are compared with the values extracted from PL modelling on a series of B doped Si QD samples. The good consistency between the values extracted by these two methods confirms the validity of the Raman model. The result confirms that Si crystallization has been suppressed by B doping as the average Si QD size and Si crystalline fraction are reduced with increased B doping level.

A highly efficient and convenient protocol was developed to access 2-amino-4H-benzothiopyran-4-ones through a process of conjugated addition–elimination. The sulfinyl group was proved to be the optimum leaving group by thorough investigations on the elimination of sulfide, sulfinyl, and sulfonyl groups at the 2-position of benzothiopyranone. Most 2-aminobenzothiopyranones were obtained in good to excellent yields under refluxing in isopropanol within 36 h. This method is base-free and the substrate scope in terms of electronic properties of the substituents of the benzothiopyranone is broad. The ten grams scale-up synthesis of the representative compounds 4a and 4d was implemented to show the practical application of this reaction, which afforded the corresponding compounds in good yields and excellent chemical purity without requiring column chromatographical purification.

An efficient visible-light-induced C H arylation of quinoxalin-2(1H)-ones in H2O is developed, which has the advantages of mild reaction conditions, environmental friendliness and good functional group tolerance. This strategy provides a simple operation method to access various 3-aryl quinoxalin-2(1H)-ones in moderate to good yields.

Mycobacterium tuberculosis (Mtb) ATP synthase is an important target for treating drug-resistant infections and sterilizing the bacteria, spurring intensive efforts to develop new TB therapeutics based on this target. In this work, four novel series including furan-2(5H)-ketone (3, 4), maleimide (5) and squaramide (6) derivatives were designed, respectively, through the strategy of scaffold morphing and hydrogen-bond introduction, using the selective Mtb ATP synthase inhibitor compound 2 as the lead compound. The result demonstrated that diamino substituted cyclobut-3-ene-1,2-dione compounds 6ab and 6ah displayed good to excellent in vitro anti-TB activities (MIC 0.452–0.963 μg/mL) with low cytotoxicity (IC50 > 64 μg/mL). In addition, not only did compound 6ab show effective activity against clinically isolated resistant strains, it also revealed good druggability profiles including improved metabolic stability, no hERG channel inhibition potential, and acceptable oral bioavailability. The preliminary result of docking study and in vitro anti-bedaquiline-resistant strain test compared to compound 2 suggested that Mtb ATP synthase is most likely the target of compound 6ab. The structure-activity relationship laid a good foundation for the identification of novel squaramides as a potential treatment of drug-resistant tuberculosis.

The application of silicon quantum dot (Si QD) based material is regarded as a promising approach for the realization of high efficiency solar cells. When silicon nanocrystals are made very small (within the vicinity of the exciton Bohr radius of bulk Si), they behave as quantum dots due to the three-dimensional quantum confinement, which could cause the material's effective optical band gap to increase. The optical band gap can be deduced from the absorption coefficient. In this paper, we analyze optical absorption and emission processes in Si QD and attempt to simulate the band-edge absorption features based on the photoluminescence spectrum. We also investigate the application of ellipsometry in the study of optical properties of Si QD thin films. Based on WVASE32 modeling tool, a homogeneous mixture model is developed to extract the absorption coefficient of this material. From these results, we extract the effective optical band gap and analyze optical properties of Si QDs materials. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Narrow size distribution of quantum dots (QDs) is needed for their application in photovoltaics but collection of such information is difficult. Many experiments have shown the photoluminescence (PL) spectrum of Si QDs will broaden and peak position is size dependent. However, there is still lack of quantitative analysis of such phenomenon. In this paper, a model is developed to fit the PL spectrum based on spontaneous emission and the size distribution of the QDs. With this model, we can quantitatively analyse the QD size and its distribution using the PL spectra only, saving the need of time consuming and destructive characterization methods such as transmission electron microscopy (TEM). The optical bandgap can be extracted naturally from this PL model. The size and distribution of the QD which are obtained by fitting the PL spectra are then confirmed by measurements using TEM and XRD.

Photolithography is used as an alternative method to overcome the challenge of making anode and cathode contacts on a Si nanocrystal solar cell deposited on non-conductive substrates instead of reactive ion etching (RIE). The advantages of this method include better control of isolation mesa fabrication and the avoidance of device exposure to highly energetic particles which may cause unpredictable damage. The photovoltaic device fabricated shows an open-circuit voltage (VOC) and a short-circuit current density (JSC) of 270 mV and 0.124 mA/cm2 respectively at room temperature under one-sun illumination. Current–voltage measurements were performed at temperatures (T) from 77 K to 300 K. A model that includes recombination-generation current in the depletion region is considered to explain the observed current behaviour of the device. An ideality factor very close to 2 was calculated based on Suns-VOC measurement, which indicates that the device is limited by recombination in the depletion region. A discrepancy was observed between the peaks (1.47 eV) in the photoluminescence spectrum and maximum VOC (0.81 V) extrapolated from the VOC–T relation at 0 K. This discrepancy has been attributed to the temperature dependence of the carrier lifetime in the depletion region characterized by an activation energy later defined in this article.

A novel series of diaryl ureas containing different linker groups were designed and synthesized. Their in vitro antitumor activity against MX-1, A375, HepG2, Ketr3 and HT-29 was evaluated using the standard MTT assay. Compounds having a rigid linker group such as vinyl, ethynyl and phenyl showed significant inhibitory activity against a variety of cancer cell lines. Specifically, compound 23 with a phenyl linker group demonstrated broad-spectrum antitumor activity with IC50 values of 5.17–6.46 μM against five tested tumor cell lines. Compound 23 is more potent than reference drug sorafenib (8.27–15.2 μM), representing a promising lead for further optimization.

A convenient and efficient synthesis of gem-difluorinated compounds is reported. The synthetic route toward various 2-substituted and 3-substituted 1,1-difluoro-6-nitro-2,3-dihydro-1H-indene derivatives is described starting from commercially available indanone. The key gem-difluorination step is accomplished in good yield by treatment of in situ generated bromine fluoride (BrF) with a dithioketal. A plausible mechanism discussing the competition between substitution and elimination is provided to rationalize the outcome of the reactions of the 3-brominated compounds with different amines.

An efficient and environmentally friendly protocol of 4H-1,3-benzoxazine-4-ones was developed based on the ring-formation of o-halogenbenzoylurea under alkaline condition with K2CO3 as the base. The method scope and limitations were also investigated. The results indicated that the electron-withdrawing ability of the substituents on the phenyl ring is beneficial to this heterocyclization.

Goodyeroside A, a natural product isolated from the Goodyera species, possesses significant hepatoprotective activity and has a novel skeleton not previously observed in other synthetic drugs used for the treatment of hepatitis. Herein, we report a highly stereoselective synthesis of goodyeroside A and related analogs with varying substituents at the α position of the carbonyl group to explore the structure-activity relationships of goodyeroside A. The absolute configuration of analog 5d was confirmed by single crystal X-ray analysis. The results from in vitro and in vivo studies indicate that 5a, the fully acetylated compound of goodyeroside A, is worthy of further investigation as a lead to identify novel hepatoprotective agents.

A series of xanthine derivatives as potent dual ligands targeting DPP-IV and GPR119 was discovered through an approach of the merged pharmacophores of GPR119 agonists and DPP-IV inhibitor linagliptin. Systematic optimization of general structure 5 led to the identification of compound 20i with selective DPP-IV inhibition, good GPR119 agonism activity and favorable metabolic stability. Docking study was performed to elucidate the potent DPP-IV inhibition of 20i. Compound 20i may serve as a tool compound for further design of anti-diabetic drugs targeting both DPP-IV and GPR119.

An improved and efficient method for synthesis of (lS,4S)-2-oxa-5-azabicyclo[2.2.1]heptane (1) from trans-4-hydroxy- l -proline was developed. Using benzyloxycarbonyl (Cbz) as protection group of amine, the reactions were in mild conditions, and the title compound 1 was accomplished in six steps in overall yield of 70%.

This paper investigated the property evolutions of Mo thin films that were subjected to post-sputtering heat treatments from 700 &deg, C to 1100 &deg, C. It was found that, after annealing, the use of Si wafers eliminated crack formations found in previously reported Mo thin films sputtered on fused silica substrates. The recrystallization of the Mo thin film was found to start at 900 &deg, C, which led to rearrangements of the preferred crystalline orientation and enhancement of grain size when the annealing temperature was further increased. The electrical conductivity of the Mo thin films was majorly affected by the increase of Mo crystallite size as the annealing temperature was increased. Overall, the improvement of material sustainability and compatibility in the high temperature annealing process has made it positive to implement a Mo-Si contact-substrate scheme for vertical structured Si QDs solar cells.

The iron-catalyzed heterocyclizations from 2-nitroanilines and benzylic alcohols to form benzimidazoles using hydrogen transfer reaction were investigated in this study. In the presence of dppf in toluene at 150 °C, various benzimidazoles were obtained in moderate to good yields within 24 h. The reaction was proposed to proceed via a cascade of alcohol oxidation, nitro reduction, condensation, and dehydrogenation.

An efficient and environmentally friendly protocol of 4H-1,3-benzoxazine-4-ones was developed based on the ring-formation of o-halogenbenzoylurea under alkaline condition with K2CO3 as the base. The method scope and limitations were also investigated. The results indicated that the electron-withdrawing ability of the substituents on the phenyl ring is beneficial to this heterocyclization.

Si quantum dots or interchangeably Si nanocrystals are promising materials for all-Si tandem solar cells in next generation photovoltaics. Si QDs in this study were fabricated by annealing sputtered Si rich oxide/SiO2 (SRO/SiO2) bilayer superlattice thin-films. Advantages of high Si content SRO layers include lower resistivity and higher light absorption cross-sections which are more suitable for photovoltaic devices. However, theoretically high Si content SRO produces greater size distribution and larger Si nanocrystals which in this case slightly lowers the bandgap towards that of crystalline Si. This study investigates the properties of high Si content SRO/SiO2 bilayer superlattice thin-films and the effect of boron and phosphorus doping.

An improved and efficient method for the preparation of torezolid based on Suzuki cross-coupling reaction as the key step was developed on a gram scale in five steps. The total yield was 44% and the optical purity of torezolid by the improved method was above 99%.

Thin films consisting of silicon nanocrystals fabricated by high silicon content in silicon rich oxide show unique properties of decreasing resistivity and increasing light absorption while maintaining quantum confinement effects. With that said, the effect of the annealing temperature and doping element on the microscopic structure of silicon nanocrystals (Si NCs) and the film are still under research. In this study, individual intrinsic, boron-, and phosphorus-doped films are annealed at various temperatures, and their structural properties are analyzed via atom probe tomography together with glancing incidence x-ray diffraction, Raman spectroscopy (Raman), transmission electron microscopy (TEM), and energy filtered TEM. In addition, photoluminescence (PL) is performed and linked with their microstructural properties. The Si NC growth is confirmed at annealing temperatures of 1000 °C and 1100 °C. The microstructure of the Si NCs in the whole film is dramatically changed by increasing the annealing tempe...

A convenient and efficient synthesis of gem-difluorinated compounds is reported. The synthetic route toward various 2-substituted and 3-substituted 1,1-difluoro-6-nitro-2,3-dihydro-1H-indene derivatives is described starting from commercially available indanone. The key gem-difluorination step is accomplished in good yield by treatment of in situ generated bromine fluoride (BrF) with a dithioketal. A plausible mechanism discussing the competition between substitution and elimination is provided to rationalize the outcome of the reactions of the 3-brominated compounds with different amines.

In this work, we conducted Capacitance-Voltage (C-V) measurement on an inverted Metal-Oxide-Semiconductor (MOS) structure device with in-situ Boron (B) doped silicon quantum dot (QD) materials as the semiconductor layer. The highly conductive P++ Si (0.001–0.005 ohmic.cm) and thermal oxide worked as the metallic gate and the dielectric layer respectively in this MOS structure. We demonstrated that there were less parasitic components in the inverted MOS in vertical structure than MOS in lateral structure. C-V curves showed clear accumulation, depletion and inversion regions as well as a frequency dispersion effect. An analysis on the equivalent circuit model and material electrical properties was presented to explain the frequency dispersion effect. We propose that the frequency dependent shift could be eliminated by removing the frequency-dependent capacitor component (C m ) in series with the ideal MOS equivalent circuit. This capacitor is possibly due to the long dielectric relaxation time in the Si QD material due to the high density of deep defects and the high resistivity. The estimated average doping level extracted from corrected C-V curves is high despite high resistivity.

The behavior of phosphine-doped Si nanocrystal material is studied in this work from the perspectives of crystallization, photoluminescence, carrier density and conductivity. Phosphine was incorporated in the material during the sputter process. It was observed that the phosphine helped to reduce the defects in the material. This was evident from the reduction of the photoluminescence of a possible defect-related energy level located at 1.30 eV, which prevailed at low temperature when phosphine was absent. Temperature dependent Hall measurement showed the carrier densities in Si nanocrystal material remained around 1019 and 1020 cm−3 from 80 K to 340 K for samples doped with 3 sccm and 9 sccm phosphine respectively during sputtering. Such metallic behavior can be due to degenerate doping in the material.

The reaction tolerates a wide range of the aromatic and heteroaromatic substituents in the benzylic alcohols and a phenylallylic alcohol but no reaction takes place when allyl- or alkyl alcohols are applied

A vertical structure with a back contact layer is suggested for silicon quantum dots (Si QDs) solar cells to overcome the current crowding effect arising from the high lateral resistance in the emitter layer of the existing mesa-structured Si QDs solar cells on quartz substrates. Molybdenum (Mo) is widely used as the back contact layer in CIGS solar cells due to its high electrical conductivity, good optical reflectance and chemical stability. This paper will focus on the feasibility of Mo as a back contact layer deposited between a quartz substrate and a sputtered silicon rich oxide (SRO) bilayers structure to obtain a fully vertical Si QDs solar cell. In this structure, the desired previously mentioned electrical and optical properties of the Mo thin film have to be maintained during and after a high temperature annealing process. This high temperature process is unavoidable in this structure as it is required to form the Si QDs. This paper aims to study factors that have impacts on critical properties of the Mo thin films processed in contact with Si and SiO2 at high temperatures. Characterizations including film thickness, microstructure, sheet resistance and optical reflectance measurements are also performed. Furthermore, interfacial properties between the Mo layer and the upper SRO bilayers are investigated.

Intrinsic, boron (B)-doped, and phosphorus (P)-doped silicon nanocrystals (Si NCs) formed from an excess Si concentration of 40 at. % were investigated to study their structural, optical, and electrical properties. Atom probe tomography (APT) revealed that the size and arrangement of Si NCs were different in each sample. A strong blue shift in photoluminescence spectra for the intrinsic and B-doped Si NCs was correlated with the volume fraction of small Si NCs. The lower resistivity of the B-doped sample than the P-doped one was explained by the percolation of Si NCs through the film.