Oxidation of p-Cresol was investigated by using ozonation process. The aim of this research is to assess the effectiveness
of ozonation on oxidation of micropollutant such as p-Cresol. Ozonation performance was evaluated based on p-Cresol
concentration reduction and chemical oxidation demand (COD) reduction. It was found ozonation at pH11 achieved
the highest p-Cresol degradation, with 95.8% of p-Cresol reduced and 96.0% of COD reduced, for an initial 50 mgL-1
of p-Cresol. The degradation of p-Cresol could be expressed by second-order of kinetic model. The second-order rate
constant k increases as the initial pH increased, but decreases with the increasing of initial p-Cresol concentrations.
Besides, the absorption spectra of p-Cresol over ozonation time were analyzed by spectrophotometry. The evolution of
absorption spectra of p-Cresol degradation suggests that the oxidation of p-Cresol follows three stages mechanisms
with cycloaddition as the first step to produce aromatic intermediates followed by ring-opening reactions, degradation
of the intermediates, and subsequently achieved mineralization.
Within a small, interconnected reaction network, orthogonal recognition processes drive the assembly and replication of a [2]rotaxane. Rotaxane formation is governed by a central, hydrogen-bonding-mediated binding equilibrium between a macrocycle and a linear component, which associate to give a reactive pseudorotaxane. Both the pseudorotaxane and the linear component undergo irreversible, recognition-mediated 1,3-dipolar cycloaddition reactions with a stoppering maleimide group, forming rotaxane and thread, respectively. As a result of these orthogonal recognition-mediated processes, the rotaxane and thread can act as auto-catalytic templates for their own formation and also operate as cross-catalytic templates for each other. However, the interplay between the recognition and reaction processes in this reaction network results in the formation of undesirable pseudorotaxane complexes, causing thread formation to exceed rotaxane formation in the current experimental system. Nevertheless, in the absence of competitive macrocycle-binding sites, realization of a replicating network favoring formation of rotaxane is possible.
The copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction has proven to be a pivotal advance in chemical ligation strategies with applications ranging from polymer fabrication to bioconjugation. However, application in vivo has been limited by the inherent toxicity of the copper catalyst. Herein, we report the application of heterogeneous copper catalysts in azide-alkyne cycloaddition processes in biological systems ranging from cells to zebrafish, with reactions spanning from fluorophore activation to the first reported in situ generation of a triazole-containing anticancer agent from two benign components, opening up many new avenues of exploration for CuAAC chemistry.
Aiming for glycolipid-based vesicles for targeted drug delivery, cationic Guerbet glycosides with spacered click functionality were designed and synthesized. The cationic charge promoted the distribution of the glycolipids during the formulation, thereby leading to homogeneously small vesicles. The positive surface charge of the vesicles stabilizes them against unwanted fusion and promotes interactions of the drug carriers with typical negative charge-dominated target cells. High bioconjugation potential of the functionalized glycolipids based on the copper-catalyzed azide alkyne cycloaddition makes them highly valuable components for targeted drug delivery systems.
The synthesis of a pentacyclic indole compound corresponding to the core structure of the misassigned indole alkaloid, tronoharine (1), is presented. The key reactions were a formal [3 + 3] cycloaddition of an indol-2-yl carbinol with an azadiene for the construction of the 6/5/6/6 tetracyclic system containing an all-carbon quaternary center and an intramolecular substitution reaction of an amine and a triflate for the creation of the bridged azepine ring. In addition, some other interesting transformations discovered during the synthetic studies are also discussed.
A series of hitherto unreported anthracene-embedded dispirooxindoles has been synthesized via a one-pot three-component 1,3-dipolar cycloaddition reaction of an azomethine ylide, generated in situ from the reaction of isatin and sarcosine to 10-benzylideneanthracen-9(10H)-one as a dipolarophile in 1-butyl-3-methylimidazolium bromide([bmim]Br), an ionic liquid. This reaction proceeded regio- and diastereoselectively, in good to excellent yields.
Novel tricyclic keto diesters have been synthesized by a one-pot three-component procedure via DABCO-catalyzed domino Knoevenagel-Michael addition reactions. Also, an efficient four-component reaction for the synthesis of another new group of tricyclic keto diesters has been developed via domino Knoevenagel-intramolecular oxo-Diels-Alder reactions. A selective thermal isomerization of the synthesized chromenes to fumarates is also described. X-ray analyses confirm unambiguously the structures of the products.
Understanding enzymatic Diels-Alder (DA) reactions that can form complex natural product scaffolds is of considerable interest. Sch 210972 1, a potential anti-HIV fungal natural product, contains a decalin core that is proposed to form through a DA reaction. We identified the gene cluster responsible for the biosynthesis of 1 and heterologously reconstituted the biosynthetic pathway in Aspergillus nidulans to characterize the enzymes involved. Most notably, deletion of cghA resulted in a loss of stereoselective decalin core formation, yielding both an endo (1) and a diastereomeric exo adduct of the proposed DA reaction. Complementation with cghA restored the sole formation of 1. Density functional theory computation of the proposed DA reaction provided a plausible explanation of the observed pattern of product formation. Based on our study, we propose that lipocalin-like CghA is responsible for the stereoselective intramolecular [4+2] cycloaddition that forms the decalin core of 1.
A series of fourteen dispiropyrrolidines were synthesized using [3+2]-cycloaddition reactions and were screened for their antimycobacterial activity against Mycobacterium tuberculosis H(37)Rv in HTS (High Throughput Screen). Most of the compounds showed moderate to good activity with MIC of less than 20 μM. Compound 4'-(4-bromophenyl)-1'-methyldispiro[acenaphthylene-1,2'-pyrrolidine-3',2″-indane]-2,1″(1H)-dione (4c) was found to be the most active with MIC of 12.50 μM.
A series of novel dimethoxyindanone embedded spiropyrrolidines were synthesized in ionic liquid, [bmim]Br and were evaluated for their inhibitory activities towards cholinesterases. Among the spiropyrrolidines, compound 4f exhibited the most potent activity with an IC50 value of 1.57 µM against acethylcholinesterase (AChE). Molecular docking simulation for the most active compound was employed with the aim of disclosing its binding mechanism to the active site of AChE receptor.