3-O-Carbamoyl-5,7,20-O-trimethylsilybins: Synthesis and Preliminary Antiproliferative Evaluation

To search for novel androgen receptor (AR) modulators for the potential treatment of castration-resistant prostate cancer (CRPC), naturally occurring silibinin was sought after as a lead compound because it possesses a moderate potency towards AR-positive prostate cancer cells and its chemical scaffold is dissimilar to all currently marketed AR antagonists. On the basis of the structure–activity relationships that we have explored, this study aims to incorporate carbamoyl groups to the alcoholic hydroxyl groups of silibinin to improve its capability in selectively suppressing AR-positive prostate cancer cell proliferation together with water solubility. To this end, a feasible approach was developed to regioselectively introduce a carbamoyl group to the secondary alcoholic hydroxyl group at C-3 without causing the undesired oxidation at C2–C3, providing an avenue for achieving 3-O-carbamoyl-5,7,20-O-trimethylsilybins. The application of the synthetic method can be extended to the synthesis of 3-O-carbamoyl-3′,4′,5,7-O-tetramethyltaxifolins. The antiproliferative potency of 5,7,20-O-trimethylsilybin and its nine 3-carbamoyl derivatives were assessed in an AR-positive LNCaP prostate cancer cell line and two AR-null prostate cancer cell lines (PC-3 and DU145). Our preliminary bioassay data imply that 5,7,20-O-trimethylsilybin and four 3-O-carbamoyl-5,7,20-O-trimethylsilybins emerge as very promising lead compounds due to the fact that they can selectively suppress AR-positive LNCaP cell proliferation. The IC50 values of these five 5,7,20-O-trimethylsilybins against the LNCaP cells fall into the range of 0.11–0.83 µM, which exhibit up to 660 times greater in vitro antiproliferative potency than silibinin. Our findings suggest that carbamoylated 5,7,20-O-trimethylsilybins could serve as a natural product-based scaffold for new antiandrogens for lethal castration-resistant prostate cancer.

Recyclable High-Performance Epoxy-Anhydride Resins with DMP-30 as the Catalyst of Transesterification Reactions

Epoxy-anhydride resins are widely used in engineering fields due to their excellent performance. However, the insolubility and infusibility make the recycling of epoxy resins challenging. The development of degradable epoxy resins with stable covalent networks provides an efficient solution to the recycling of thermosets. In this paper, 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) is incorporated into the epoxy-glutaric anhydride (GA) system to prepare high-performance epoxy resins that can be recycled below 200 °C at ordinary pressure via ethylene glycol (EG) participated transesterification. The tertiary amine groups in DMP-30 can catalyze the curing reaction of epoxy and anhydride, as well as the transesterification between ester bonds and alcoholic hydroxyl groups. Compared with early recyclable anhydride-cured epoxy resins, the preparation and recycling of diglycidyl ether of bisphenol A (DGEBA)/GA/DMP-30 systems do not need any special catalysts such as TBD, Zn(Ac)2, etc., which are usually expensive, toxic, and have poor compatibility with other compounds. The resulting resins have glass transition temperatures and strengths similar to those of conventional epoxy resins. The influences of GA content, DMP-30 content, and temperature on the dissolution rate were studied. The decomposed epoxy oligomer (DEO) is further used as a reaction ingredient to prepare new resins. It is found that the DEO can improve the toughness of epoxy resins significantly. This work provides a simple method to prepare readily recyclable epoxy resins, which is of low-cost and easy to implement.

Reactions related with hydroxyl, carboxyl and alkyl side chain at different temperature stages and the effects on low-rank coal ignition

Low-rank coal contains abundant hydroxyl, carboxyl and alkyl side chains, and reactions related to these groups are the main reason for the spontaneous combustion of low-rank coal. Here, two different low-rank coals (BRXL, YJL52) are selected. Firstly, the ignition temperatures of the coals are determined by thermogravimetric method. Secondly, the coals are heated at 100°C temperature intervals before the ignition temperature in the thermogravimetry, and infrared measurement is performed to explore the changes of these groups. Combining previous studies in the literatures with infrared analysis, it is found that reactions related are as follows: phenolic hydroxyl converting into alcoholic hydroxyl, alcoholic hydroxyl further oxidizing to carboxyl, and carboxyl decarboxylating into alkyl side chains. After that, the changes of phenolic hydroxyl and carboxyl on the surface of the coal at 100°C temperature intervals are determined by titration, which further reveal the main reactions occurred in every temperature interval. Additionally, the actual heat release in different temperature ranges is discussed with the reaction enthalpies of the above-mentioned main reactions. As a result, the key temperature stage that causes spontaneous combustion is found. The screening study in this paper on the reaction of low-rank coal before spontaneous combustion provides a theoretical basis for the control of spontaneous combustion of low-rank coal.

Biocarbon Meets Carbon—Humic Acid/Graphite Electrodes Formed by Mechanochemistry

Humic acid (HA) is a biopolymer formed from degraded plants, making it a ubiquitous, renewable, sustainable, and low cost source of biocarbon materials. HA contains abundant functional groups, such as carboxyl-, phenolic/alcoholic hydroxyl-, ketone-, and quinone/hydroquinone (Q/QH2)-groups. The presence of Q/QH2 groups makes HA redox active and, accordingly, HA is a candidate material for energy storage. However, as HA is an electronic insulator, it is essential to combine it with conductive materials in order to enable fabrication of HA electrodes. One of the lowest cost types of conductive materials that can be considered is carbon-based conductors such as graphite. Herein, we develop a facile method allowing the biocarbon to meet carbon; HA (in the form of a sodium salt) is mixed with graphite by a solvent-free mechanochemical method involving ball milling. Few-layer graphene sheets are formed and the HA/graphite mixtures can be used to fabricate HA/graphite hybrid material electrodes. These electrodes exhibit a conductivity of up to 160 S·m−1 and a discharge capacity as large as 20 mAhg−1. Our study demonstrates a novel methodology enabling scalable fabrication of low cost and sustainable organic electrodes for application as supercapacitors.

Organobase-Catalyzed Hydroxyl-yne Click Polymerization

The proposition of click chemistry has provided a quick channel for saccharides modification, which has always been worth exploring. Click reaction of hydroxyl groups possessed by saccharides is thus highly desirable to be developed. In this paper, we report hydroxyl-yne click polymerization using ester activated alkynes and alcoholic hydroxyl groups. The polymers, poly(vinyl ether ester)s (PVEEs), were obtained with high weight-average molecular weights up to 71 000 were obtained in excellent yields up to 99% using a commercially organic base of bicyclo[2.2.2]-1,4-diazaotane (DABCO) as catalyst under ambient conditions. The obtained polymers possess high thermal stability and low cytotoxicity. Both semi-crystalline and amorphous polymers were obtained due to the different flexibility of monomers. Upon incorporating aggregation-induced emission (AIE) moiety of tetraphenylethylene (TPE), the resultant polymers displayed typical AIE characteristics. This work provides a potential strategy for saccharides modification via the hydroxyl-yne click reaction.

Organobase-Catalyzed Hydroxyl-yne Click Polymerization

The proposition of click chemistry has provided a quick channel for saccharides modification, which has always been worth exploring. Click reaction of hydroxyl groups possessed by saccharides is thus highly desirable to be developed. In this paper, we report hydroxyl-yne click polymerization using ester activated alkynes and alcoholic hydroxyl groups. The polymers, poly(vinyl ether ester)s (PVEEs), were obtained with high weight-average molecular weights up to 71 000 were obtained in excellent yields up to 99% using a commercially organic base of bicyclo[2.2.2]-1,4-diazaotane (DABCO) as catalyst under ambient conditions. The obtained polymers possess high thermal stability and low cytotoxicity. Both semi-crystalline and amorphous polymers were obtained due to the different flexibility of monomers. Upon incorporating aggregation-induced emission (AIE) moiety of tetraphenylethylene (TPE), the resultant polymers displayed typical AIE characteristics. This work provides a potential strategy for saccharides modification via the hydroxyl-yne click reaction.

BIOFUEL VIA INTERESTERIFICATION OF RAPESEED OIL WITH METHYL ACETATE IN PRESENCE OF POTASSIUM t-BUTOXIDE/THF

Transesterification does not allow to make full conversion of oil to biodiesel because the by-product glycerol cannot be included in the composition of biofuel. Interesterification constitutes a full conversion process with production of triacetin (TA) instead of glycerol, which can be included in the composition of biofuel and allows to increase its yield. Both interesterification and transesterification effectively occur only in presence of catalysts. Results of the investigation of heterogeneous and homogeneous catalysts indicate the superior importance of catalyst solubility in starting reaction mixture. Partial solubility can remarkably lower the activity of homogeneous catalyst and extremely increase that of formally heterogeneous one. The reaction mixture of interesterification reaction is less polar than that of transesterification, and potassium tert-butoxide (t-BuOK) should be more appropriate catalyst for interesterification than sodium methoxide which is used in most cases. The catalytic system t-BuOK/t-BuOH substantially increases the yield of TA and changes the properties of obtained biofuel. Whereas the content of the TA in the interesterification reaction mixture does not achieve the same level from the theoretically predicted as the FAME, the occurrence of side reaction between t-BuOH and TA cannot be excluded. This paper presents a study of the interesterification of rapeseed oil in presence of catalytic system t-BuOK/THF (catalytic system without alcohols) with the aim of establishing the influence of aprotic tetrahydrofuran to the proceeding the reaction, composition of reaction mixtures and their fuel properties. Obtained results show that the absence of alcoholic hydroxyl groups in the catalytic system insufficiently increases the activity of catalytic system but fails to increase the yield of FAME.

Study on the Oxidative Leaching of Uranium from the Lignite in the CO32-/HCO3- System

Na2CO3/NaHCO3 mixtures with different oxidants were used to leach uranium in the lignite which was obtained from Lincang, Yunnan province. The experimental results showed that the optimal solid/liquid ratio and CO32-/HCO3- ratio for uranium leaching were 1 : 20 (g/mL) and 2 : 1, respectively. With the increase of carbon concentration from 0.1 mol/L to 1.1 mol/L, the leaching efficiency of uranium increased from 14.64% to 42.39% after 6 h leaching. The oxidants could significantly enhance the uranium leaching efficiency, which was up to 72.23% by injecting O2 at 1.5 L/min after 12 h leaching. The oxidative leaching process of uranium from the lignite was better fitted to the pseudo-second-order reaction model. The sequential extraction results illustrated that the oxidants could effectively enhance the leaching of organic matter bound uranium in the lignite, which was decreased from 76.86 mg/kg to 9.00 mg/kg by injecting O2. The infrared spectrum analysis demonstrated that the corresponding transmittance at about 3197 cm−1 was prominently reduced after the oxidative leaching, which intimated that the phenolic and alcoholic hydroxyl might be the main functional groups combined with uranium in the lignite.