In this paper, highly selective core-shell molecularly imprinted polymers (MIPs) of tadalafil on the surface of magnetic nanoparticles (MNPs) were prepared. Three widely used functional monomers 2-(trifluoromethyl) acrylic acid (TFMAA), acrylic acid (AA), and methacrylic acid (MAA) were compared theoretically as the candidates for MIP preparation. MIP-coated magnetic nanoparticles (MIP-coated MNPs) showed large adsorption capacity, high recognition ability, and fast binding kinetics for tadalafil. Furthermore, because of the good magnetic properties, MIP-coated MNPs can achieve rapid and efficient separation with an external magnetic field simply. The resulting MIP-coated MNPs were used as dispersive solid-phase extraction (DSPE) materials coupled with HPLC-UV for the selective extraction and detection of tadalafil from medicines (herbal sexual health products). Encouraging results were obtained. The amounts of tadalafil that were detected from the herbal sexual health product was 43.46 nmol g(-1), and the recoveries were in the range of 87.36-90.93% with the RSD < 6.55%.
The highly enantioselective cinchona alkaloid-catalyzed Mannich reaction of dicarbonyl compounds with alpha-amido sulfones as acyl imine precursors is described. The reaction requires 10 mol % of the cinchona alkaloid catalyst, which serves as a general base to generate acyl imines in situ, and aqueous Na2CO3 to maintain the concentration of free alkaloid catalyst. The reaction products are obtained in good yields and high enantioselectivities, and in diastereoselectivities that range from 1:1 to >95:5. The cinchonine-catalyzed reactions provide practical access to highly functionalized building blocks which have been employed in the synthesis of chiral dihydropyrimidones, a class of compounds rich in diverse biological activity. Dihydropyrimidone modifications include a highly diastereoselective hydrogenation of the enamide moiety, using an H-Cube flow hydrogenator and a Rh(II)-mediated 1,3-dipolar cycloaddition to afford highly functionalized complex heterocycles.
The first asymmetric synthesis of 1,2-dioxolane-3-acetic acids is reported. Key features include the stereoselective opening of enantiomerically enriched oxetanes by hydrogen peroxide, conversion of the resulting 4-hydroperoxy-2-alkanols to 3-alkoxy-1,2-dioxolanes, and Lewis acid mediated homologation of the latter with a thioester silyl ketene acetal. The approach is modeled on 3,5-dimethyl-5-hexadecyl-1,2-dioxolane-3-acetic acid (1a), an unnamed natural product, and an optimized strategy is applied to the synthesis of four stereoisomers of plakinic acid A (2), allowing a configurational assignment of this incompletely characterized natural product.
An efficient general method using a clean and transition-metal-free photochemical strategy for the direct Csp 2 -H radical difluoromethylation of coumarins with HCF 2 SO 2 Na was developed. The visible-light-promoted strategy proceeds with 5 mol % Eosin Y under mild reaction conditions and showed excellent functional group compatibility. The control experiments illustrated that O 2•− participated in this process and plays an important role in the reactions. Moreover, the representative products exhibited excellent antifungal activities in vitro. It was noted that the EC 50 value of compound 3a was determined to be as low as 1.5463 μg/mL against Rhizoctorzia solani, which was better than Boscalid (EC 50 = 2.9767 μg/mL).
In an effort to expand the stereochemical and structural complexity of chemical libraries used in drug discovery, the Center for Chemical Methodology and Library Development at Boston University has established an infrastructure to translate methodologies accessing diverse chemotypes into arrayed libraries for biological evaluation. In a collaborative effort, the NIH Chemical Genomics Center determined IC 50 's for Plasmodium falciparum viability for each of 2,070 members of the CMLD-BU compound collection using quantitative high-throughput screening across five parasite lines of distinct geographic origin. Three compound classes displaying either differential or comprehensive antimalarial activity across the lines were identified, and the nascent structure activity relationships (SAR) from this experiment used to initiate optimization of these chemotypes for further development.T he synthesis of compound libraries embodying structural diversity and complexity is one potential avenue to enabling the discovery of potent and selective bioactive agents (1-3). Synthetic methodology aimed at library design and distribution is the focus of the Center for Chemical Methodology and Library Development at Boston University (CMLD-BU). Currently the CMLD-BU maintains a collection of approximately 2,500 compounds derived from reaction methodologies developed in the Center and associated groups. The CMLD-BU has developed a workflow that leverages focused methodology development (4) and identification of new scaffolds and chemical reactions utilizing multidimensional reaction screening (5) for the synthesis of libraries.In a collaboration between the CMLD-BU and the NIH Chemical Genomics Center (NCGC), an effort to discover unique chemotypes which inhibit the viability of P. falciparum, the causative agent of malaria, is underway. Malaria not only inflicts tremendous suffering and morbidity on the human population, but has dramatically influenced the course of civilization with profound sociological and economic implications (6). In response, there have been significant screening efforts for new antimalarial agents (7,8). Effective treatments continue to be needed in part due to acquired resistance of P. falciparum. Identification of molecular targets affecting the viability of malaria is necessary for efficient drug development as is the discovery of chemotypes active across a variety of geographic isolates. With an aim to improve the process of identifying new compounds and targets, we have used quantitative high-throughput screening (qHTS) to achieve pharmacological fingerprints of chemical libraries (9). This technique tests each compound as a seven point titration covering four orders of magnitude in concentration thus allowing sufficient resolving power by virtue of IC 50 determinations to reveal subtle differences in compound activities between parasite lines. A compound with a differential chemical phenotype (DCP) can enable mapping of target genes using genetic recombination wherein the DCP emerges between two or more...
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