Total Synthesis of Tricladins A and B and Identification of Their Absolute Configuration

A concise synthesis of both (<i>S</i>)- and (<i>R</i>)-enantiomers of tricladins A and B from l-Boc alanine was achieved. The diastereomeric intermediates were separated by chiral column chromatography, and the absolute configuration of the 2-position was assigned by observed NOE interactions with the known stereogenic center at the 5-position. By comparison of all synthesized final enantiomers with the corresponding natural products, we concluded that the natural tricladins A and B must have the (<i>R</i>)-configuration

Enhanced degradation of nitrobenzene by combined ultrasonic irradiation and a zero-valent zinc catalyst

<p>Enhanced ultrasonic catalytic activity in nitrobenzene degradation was found by combining ultrasonic irradiation and a zero-valent zinc (Zn⁰) catalyst. In this system, the influence of the reaction parameters, reaction kinetics, intermediates, and mechanism was investigated. Under the optimum conditions (initial nitrobenzene concentration of 0.01 mmol/L, Zn⁰ dosage of 0.4 g/L, initial pH 7, ultrasonic intensity 4.0 W/cm²), approximately 91.2% of nitrobenzene could be removed within 30 min. The degradation process followed the pseudo-first-order kinetics model, and the reaction rate constant was 0.0670 min⁻¹. The mechanism of the synergetic effect of ultrasound and Zn⁰ was proposed. Three intermediates of nitrophenol, phenylhydroxylamine, and aniline were identified by liquid chromatography–mass spectrometry (LC-MS). The degradation pathways of hydroxyl radical oxidation and Zn⁰ reduction were deduced. This combined system is promising for the removal of nitrobenzene pollutants from water.</p

Living/Controlled Polymerization of Renewable Lignin-Based Monomers by Lewis Pairs

It is a challenging task to replace the traditional petroleum-based monomers with the biorenewable monomers for polymer synthesis, as it can alleviate the energy and environmental crises. Lewis pairs (LP) composed of organophosphorus superbases and organoaluminum Lewis acid are employed to rapidly and quantitatively transform a series of biorenewable monomers derived from the lignin degradation products into polymers with predicted molecular weight (Mn up to 519 kg mol–1) and small Đ value (as low as 1.10). The livingness of the polymerization of lignin-based monomer by such LP system can be also verified by the following evidence, including a linear increase of polymer Mn vs monomer-to-initiator ratio and monomer conversion and high end-group fidelity as evidenced by successful chain extensions and synthesis of well-defined block copolymers. More impressively, the lignin-based copolymers with methyl ferulate exhibited fluorescence response under the irradiation of UV light at 365 nm, suggesting application potential of the lignin-based polymers in biological imaging, information storage, and anti-counterfeiting materials

Spatial changes of NSI (a) and NUE (b) during 2000–2010 in the Yangtze River Basin.

<p>Spatial changes of NSI (a) and NUE (b) during 2000–2010 in the Yangtze River Basin.</p

The Process of acquisition of the bourgeoisie in the early modern society - the example of New Town in Prague in the years 1582-1612

Diploma thesis "The proces of acquisition of the bourgeoisie in the early modern society - the example of New Town in Prague in the years 1582 - 1612" deals with the processes related to the acquisition of burgher rights during the reign of Rudolph II., focusing on the formation of the relationship odopted townsmen - surety; craft and the place of origin by acquirer burgher rights. Powered by TCPDF (www.tcpdf.org

Factors associated with the change of synthetic fertilizer N application rate and cropland area in upper, middle and lower reaches of the Yangtze River Basin.

<p>Factors associated with the change of synthetic fertilizer N application rate and cropland area in upper, middle and lower reaches of the Yangtze River Basin.</p

Contributions of various parameters to variability of N budget of 2000.

<p>Contributions of various parameters to variability of N budget of 2000.</p

Relative contributions of cropland area and synthetic fertilizer N application rate to fertilizer N input during 2000–2010.

<p>Relative contributions of cropland area and synthetic fertilizer N application rate to fertilizer N input during 2000–2010.</p

Factors associated with the change of synthetic fertilizer N application rate and cropland area in upper, middle and lower reaches of the Yangtze River Basin.

<p>Factors associated with the change of synthetic fertilizer N application rate and cropland area in upper, middle and lower reaches of the Yangtze River Basin.</p

Location of the Yangtze River Basin in China.

<p>Location of the Yangtze River Basin in China.</p