Biosynthesis of providencin: understanding photochemical cyclobutane formation with density functional theory

The unique structure of furanocembranoid natural product providencin has stimulated biosynthetic hypotheses, especially concerning the formation of its cyclobutanol ring. One such hypothesis involves a photochemically induced Norrish–Yang cyclization in bipinnatin E. We have used computations to assess the feasibility and the stereochemical outcome of this proposed biosynthetic transformation. Density functional theory calculations reveal that the proposed Norrish–Yang cyclization in bipinnatin E is possible and that the stereoselectivity of this step is consistent with that of the natural product

Thermal and photochemical mechanisms for cyclobutane formation in bielschowskysin biosynthesis

The unique structure of furanocembranoid natural product bielschowskysin has provoked a number of biosynthetic hypotheses: quantum chemical calculations provide a means to assess the feasibility of postulated mechanisms in the construction of this unusual carbon skeleton. Calculations reveal that thermal closure is possible in water via an unusual concerted cyclobutane-forming transition state without the intervention of an enzyme. Photocycloaddition is computed to be extremely efficient, provided enol ether triplet sensitization can be achieved by an appropriate light source. The possible existence of a stable dicarbonyl intermediate presents a challenge for the thermal route, implicating a photochemical pathway in bielschowskysin biosynthesis

Metal-free base-mediated oxidative annulation cascades to 3-substituted-3-hydroxyoxindole and its 3-spirocyclic derivative

A simple and efficient method was developed for the construction of the medicinally important 3-substituted-3-hydroxyoxindoleand its 3-spirocyclic derivativeswith readily available aniline derivatives as starting materials. Thishighly atom-and step-economical one-pot protocolwas carried out undermetal-freebase-mediated conditions througha novel oxidative annulationstrategywith oxygen as the oxidant.The key intermediates were isolated and confirmed.A reasonablereaction pathway was proposed and supported by both the preliminary experiments and computational studies

Synthesis of an isomer of lycoplanine a via cascade cyclization to construct the spiro-N,O-acetal moiety

An isomer of lycoplanine A with a 6/10/5/5 tetracyclic skeleton was synthesized using D–A reaction and cascasde reaction to respectively construct the [9.2.2] pentadecane skeleton and the challenging 1-oxa-6-azaspiro[4.4]nonane spirocenter. Morever, detailed DFT calculations were conducted to explain the selectivity in the D–A reaction. This study may provide sufficient experience for the total synthesis of lycoplanine A and other alkaloids with similar spiro-N,O-acetal cores

Advances on transition metal oxides catalysts for formaldehyde oxidation:a review

This article highlights recent advances in the development of transition metal-based catalysts for formaldehyde oxidation, particularly the enhancement of their catalytic activity for low-temperature oxidation. Various factors that enhance low-temperature activity are reviewed, such as morphology and tunnel structures, synthesis methods, specific surface area, amount and type of active surface oxygen species, oxidation state, and density of active sites are discussed. In addition, catalyst immobilization for practical air purification, reaction mechanism of formaldehyde oxidation, and the reaction parameters affecting the overall efficiency of the reaction are also reviewed

Machine-Learning-Enabled Virtual Screening for Inhibitors of Lysine-Specific Histone Demethylase 1

A machine learning approach has been applied to virtual screening for lysine specific demethylase 1 (LSD1) inhibitors. LSD1 is an important anti-cancer target. Machine learning models to predict activity were constructed using Morgan molecular fingerprints. The dataset, consisting of 931 molecules with LSD1 inhibition activity, was obtained from the ChEMBL database. An evaluation of several candidate algorithms on the main dataset revealed that the support vector regressor gave the best model, with a coefficient of determination (R2) of 0.703. Virtual screening, using this model, identified five predicted potent inhibitors from the ZINC database comprising more than 300,000 molecules. The virtual screening recovered a known inhibitor, RN1, as well as four compounds where activity against LSD1 had not previously been suggested. Thus, we performed a machine-learning-enabled virtual screening of LSD1 inhibitors using only the structural information of the molecules

Mechano‐fenton–piranha oxidation of carbon nanotubes for energy application

Emission of nitrogen oxides (NOx) from chemical processing of materials is a serious environmental concern, frustrating the development of many innovative technologies. For example, sulfonitric oxidation is the most widely used method for processing carbon nanotubes (CNTs), producing a large amount of NOx. As a result, large scale applications of CNTs for downstream purposes remain challenging. Herein, a NOx-free oxidation method is proposed for CNTs processing. It starts with mechanically grinding, and then oxidizing the CNTs by hydroxyl radicals in sealed reactors. Such processed CNTs are shorter, possess balanced surface oxygen containing groups without compromising the original CNT integrity, and can disperse readily in water. These are desirable for making various CNT composites, including those with conducting polymers for supercapacitors. The reactors in the process are industrially adoptable, promising a great technological and commercial future

Heliaquanoids A–E, five sesquiterpenoid dimers from Inula helianthus-aquatica

Heliaquanoid A (1), the first exo-2,4-linked Diels−Alder adduct between a pseudoguaianolide dienophile and a guaianolide diene, and heliaquanoids B−E (2−5), four new 2,4-linked Diels−Alder adducts between a xanthanolide dienophile and a guaianolide diene, were isolated from stems and leaves of Inula helianthus-aquatica. Their structures were determined by the NMR spectroscopy, modified Mosher′s method, electronic circular dichroism, and X-ray diffraction analysis. Compounds 2 and 3 exhibited moderate cytotoxic activities against HL-60 cells with IC50 values of 7.5 and 4.9 μM, respectively

A comparative study of Mn/Co binary metal catalysts supported on two commercial diatomaceous earths for oxidation of benzene

Two commercial diatomaceous earths were used as supports for the preparation of Mn/Cobinary metal catalysts at different metal loads (5 to 10 wt % Mn and 5 to 15 wt % Co) by incipientwetness deposition. The activity of the prepared catalysts towards the complete oxidation of benzeneto CO2and water was investigated between 100 and 400◦C. Raw supports and synthesized catalystswere characterized by XRD, N2physisorption, SEM-EDS, H2-TPR, and TPD. The purificationtreatment of food-grade diatomite significantly affected the crystallinity of this support whilereducing its specific surface area (SSA). A loss of SSA, associated with the increase in the metalload, was observed on samples prepared on natural diatomite, while the opposite trend occurredwith food-grade diatomite-supported catalysts. Metal nanoparticles of around 50 nm diameter wereobserved on the catalysts’ surface by SEM analysis. EDS analysis confirmed the uniform depositionof the active phases on the support’s surface. A larger H2consumption was found by TPR analysisof natural diatomite-based samples in comparison to those prepared at the same metal load onfood-grade diatomite. During the catalytic oxidation experiment, over 90% conversion of benzenewere achieved at a reaction temperature of 225◦C by all of the prepared samples. In addition, theformation of coke during the oxidation tests was demonstrated by TGA analysis and the solublefraction of the produced coke was characterized by GC-MS