Study on asymmetric syntheses of steroids: XIII. Synthesis of two new (±)-3-oxa-A-nor steroids 1a and 1b

This paper deals with the synthesis of two new (±)-3-oxa-A-nor steroids 1a and 1 b. The conjugated addition of 5′-methylfurandithane anion 8b to the CD-ring synthon 9 in HMPA-THF afforded 9, 10-seco-3-oxa-A-nor steroid 22. The intramolecular cyclization of 22 in acidic medium gave 23, which underwent hydrolytic desulfurization at elevated temperature in acidic medium to give 1b. The desulfurization of 23 over Raney nickel gave 1a.     

Studies on the identification and synthesis of insect pheromone: XXIV. Synthesis of (7R, 8S)-(+)- and (7S, 8R)-(−)-sex pheromone of gypsy moth and stereochemistry of β-hydroxysilane

Condensation of the epoxy aldehyde 2 or 2 prepared by Sharpless asymmetric epoxydation in 96—97% yield, with trimethylsilane lithiated 3 gave 7 or 7 ′, which after transformation to the corresponding acetoxyl compound 8 or 8 ′ afforded the title compound 1a or 1b via β-acetoxysilane elimination and catalytic homogeneous hydrogenation. The configurations of the stereoisomers 7 and 7 ′ were determined.     

Studies on steroidal plant-growth regulator: VII. Synthesis of 2α, 3α-dihydroxy-7-oxa-6-oxo-23, 24-dinor-B-homo-5α-cholanic acid and 2α, 3α-dihydroxy-7-oxa-6-oxo-24-nor-B-homo-5α-cholanic acid

Two brassinolide analogues, (2) and (3), have been synthesized from hyodeoxycholic acid (4) through a sequence of reactions as shown in Scheme 1 and 2 of the text.     

过充电保护添加剂1,4-二甲氧基苯的反应机理

采用密度泛函理论(B3LYP/6-311+G(d,p))和MP2/6-311+G(d,p)方法,研究锂离子电池过充电保护添加剂1,4-二甲氧基苯(p-DMOB)的作用机理.计算结果表明,在过充时,p-DMOB优先于溶剂分子(乙基甲基碳酸酯、二甲基碳酸酯、碳酸乙酯)发生氧化反应.用B3LYP和MP2计算所得的p-DMOB理论氧化电位接近,分别为4.12和4.05V(vsLi/Li+).p-DMOB氧化时首先失去一个电子,生成p-DMOB+·正离子自由基,用B3LYP和MP2方法计算所得的相应能量变化分别为701.24和728.27kJ·mol-1.失去电子后苯环的共轭性受到破坏,随后p-DMOB+·苯环上的C―H键发生断裂,失去H+并形成p-DMOB·自由基.用B3LYP和MP2方法计算所得的相应能量变化分别为1349.78和1810.99kJ·mol-1.p-DMOB·自由基很不稳定,会在电极表面发生聚合反应形成聚合物膜,用B3LYP和MP2方法计算所得的相应能量变化分别为-553.37和-1331.20kJ·mol-1.     

Dynamic crossover in hydration water of curing cement paste: the effect of superplasticizer

The influence of a new comb-shaped polycarboxylate-based superplasticizer (CSSP) on the hydration kinetics and transport properties of aged cement pastes has been investigated by high-resolution quasi-elastic neutron scattering (QENS) and low temperature differential scanning calorimetry (LT-DSC). A new method of analysis of QENS spectra is proposed. By applying the refined method we were able to access to four independent physical parameters including the self-diffusion coefficient of the hydration water confined in the cement paste. Mean squared displacement (MSD) of the hydrogen atom for mobile water molecules displays a dynamic crossover temperature in agreement with DSC data. The experimental results indicate that CSSP polymer added into cement paste moderates the hydration process and decreases the dynamic crossover temperature of the hydration water.     

Spirally configured cis-stilbene/fluorene hybrids as bipolar, organic sensitizers for solar cell applications

Hybrids based on a dibenzosuberene core bearing a spiro-fluorene junction at the C-5 position and with amino donor and β-thiophenyl-α-cyanoacrylic acid acceptor groups at C-3 and C-7, respectively, serve as new organic sensitizer materials for solar cell applications. Solar cell devices based on these materials show a conversion efficiency (η) of up to 6.1% (V(oc) = 697 mV, J(sc) = 12.2 mA cm(-2), FF = 0.72) under AM 1.5 G conditions. The best IPCE values exceed 75% within the 450-550 nm absorption range.     

Miniaturized Salinity Gradient Energy Harvesting Devices

Harvesting salinity gradient energy, also known as “osmotic energy” or “blue energy”, generated from the free energy mixing of seawater and fresh river water provides a renewable and sustainable alternative for circumventing the recent upsurge in global energy consumption. The osmotic pressure resulting from mixing water streams with different salinities can be converted into electrical energy driven by a potential difference or ionic gradients. Reversed-electrodialysis (RED) has become more prominent among the conventional membrane-based separation methodologies due to its higher energy efficiency and lesser susceptibility to membrane fouling than pressure-retarded osmosis (PRO). However, the ion-exchange membranes used for RED systems often encounter limitations while adapting to a real-world system due to their limited pore sizes and internal resistance. The worldwide demand for clean energy production has reinvigorated the interest in salinity gradient energy conversion. In addition to the large energy conversion devices, the miniaturized devices used for powering a portable or wearable micro-device have attracted much attention. This review provides insights into developing miniaturized salinity gradient energy harvesting devices and recent advances in the membranes designed for optimized osmotic power extraction. Furthermore, we present various applications utilizing the salinity gradient energy conversion.     

Studies on the structures and syntheses of arteannuin and related compounds: XVI. Synthesis of arteannuin E and epoxy fission reaction of methyl α-epoxy arteannuinate

Arteannuin E was synthesized from methyl β-epoxy arteannuinate by treatment with formic acid followed by hydrolysis and lactonization. Methyl α-epoxy arteannuinate or methyl α-epoxy dihydroarteannuinate treated with formic acid did not produce the trans-diaxial product. Arteannuin E (1) and arteannuin F (2) exist together with the arteannuin (3) in Artemisia annua L.¹ The structures were determined¹ and 2 was synthesized.² The structure difference lies in the different fusion of their lactone rings. In this paper we will report the synthesis of 1 and the epoxy fission reaction of the methyl α-epoxy arteannuinate (4).     

猪去氧胆酸的化学Ⅰ.△~5-7-酮胆烷酸甲酯系列的还原研究

猪去氧胆酸(1)是我国甾体资源之一,它和有生理活性的鹅去氧胆酸(2),熊去氧胆酸(3)在结构上十分相似。从猪去氧胆酸(1)合成2和3的关键是保留A/B环顺式稠合,同时使6α-羟基移位成7α-或7β-羟基。文献报道     

Studies on steroidal plant growth regulator——27.Stereoselective construction of the side chain of brassinosteroid by employing a separated dialkylation and a tandem dialkylation of the pyranone moiety

A stereocontrolled construction of the side chain of brassinosteroid was developedvia the separated dialkylation and the tandem dialkylation of the pyranone moiety as the keystep.