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Emergence of library-based approaches have changed the way of developing new functional molecules in materials science and pharmaceutical science. Therefore, reliable methods for rapid and systematic generation of functional molecules are highly called for in this field. We herein describe our concept of "platform synthesis" as a useful strategy for generating molecular diversity. This simple yet powerful strategy realizes the synthesis of a number of interesting multifunctional molecules, such as multisubstituted olefins, in a programmable and diversity-oriented format. As well as applications to the synthesis of pharmaceutically important molecules, such as tamoxifen and CDP840, applications to materials science, which have led to the discovery of interesting fluorescent materials and properties, are also described.  相似文献   

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The solid-phase synthesis of diverse sets of 1,3-thiazine-5-carboxylates on Wang resin is described. Acetoacetylation, followed by Knoevenagel condensation and an acid-promoted ring-closure reaction with thioureas furnished polymer-bound 1,3-thiazines. As an alternative to transesterification, a de-novo synthesis of beta-keto esters, starting from polymer-bound malonic acid through reaction with acyl imidazoles, was applied to increase the diversity. To reduce contamination, an on-bead purification of resin-bound 1,3-thiazines that makes use of differences in the reactivity of ester bonds toward alkoxides is reported. A final four-step post-cleavage modification of thiazine-5-carboxylates, derived by TFA cleavage from the Wang linker, leads to esters or amides. Twenty 1,3-thiazines were obtained in yields of up to 61 % over either 9 or 13 steps.  相似文献   

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Organocalcium chemistry is still in its infancy. The direct synthesis of activated calcium and (substituted) iodobenzenes allows for the large-scale and high-yield synthesis of aryl calcium iodides. The influence of the substitution patterns of the phenyl group, halogen atom, and solvent is discussed. Aryl calcium iodides show a Schlenk equilibrium that enables the isolation of diaryl calcium derivatives. Owing to the high reactivity of aryl calcium halides, low temperatures have to be maintained throughout the preparative procedures in order to avoid side reactions. A decrease of reactivity and, hence, an enhanced stability at higher temperatures can be achieved by shielding of the calcium atom by increasing the coordination number of the metal center or by substitution of the iodide anion by bulky groups.  相似文献   

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Some lichens were recently reported to modify the surface state of asbestos. Here we report some new insight on the physico-chemical modifications induced by natural chelators (lichen metabolites) on two asbestos samples collected in two different locations. A biomimetic approach was followed by reproducing in the laboratory the weathering effect of lichen metabolites. Norstictic, pulvinic and oxalic acid (0.005, 0.5 and 50 mM) were put in contact with chrysotile fibres, either in pure form (A) or intergrown with balangeroite, an iron-rich asbestiform phase (B). Mg and Si removal, measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), reveals an incongruent dissolution for pure chrysotile (A), with Mg removal always exceeding that of Si, while chrysotile-balangeroite (B) follows a congruent dissolution pattern in all cases except in the presence of 50 mM oxalic acid. A much larger removal of Mg than Si in the solutions of 0.5 and 50 mM oxalic acid with chrysotile (A) suggests a structural collapse, which in the case of chrysotile-balangeroite (B) only occurs with 50 mM oxalic acid; in these cases both samples are converted into amorphous silica (as detected by X-ray diffraction (XRD)). Subsequent to incubation, some new phases (Fe(2)O(3), CaMg(CO(3))(2), Ca(C(2)O(4)) x H(2)O and Mg(C(2)O(4))2 x H(2)O), similar to those observed in the field, were detected by XRD and micro-Raman spectroscopy. The leaching effect of lichen metabolites also modifies the Fenton activity, a process widely correlated with asbestos pathogenicity: pure chrysotile (A) activity is reduced by 50 mM oxalic acid, while all lichen metabolites reduce the activity of chrysotile-balangeroite (B). The selective removal of poorly coordinated, highly reactive iron ions, evidenced by NO adsorption, accounts for the loss in Fenton activity. Such fibres were chemically close to the ones observed in the field. Chrysotile-rich rocks, colonised by lichens, could be exposed to a natural bioattenuation and considered as a transient environmental hazard.  相似文献   

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The main approaches that have been taken to chemically modify polymer surfaces are introduced and reviewed. These are wet chemical oxidation, plasma treatment, classical organic chemistry, and attachment of polymer chains. The extent to which each of these approaches can produce the specific modifications desired is discussed, and any unwanted effects that commonly occur are cited. Finally, the need for using several methods of surface analysis in concert to obtain adequate surface characterization is described.  相似文献   

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How biomembranes are self‐organized to perform their functions remains a pivotal issue in biological and chemical science. Understanding the self‐assembly principles of lipid‐like molecules hence becomes crucial. Herein, we report the mesostructural evolution of amphiphilic sphere‐rod conjugates (giant lipids), and study the roles of geometric parameters (head–tail ratio and cross‐sectional area) during this course. As a prototype system, giant lipids resemble natural lipidic molecules by capturing their essential features. The self‐assembly behavior of two categories of giant lipids (I‐shape and T‐shape, a total of 8 molecules) is demonstrated. A rich variety of mesostructures is constructed in solution state and their molecular packing models are rationally understood. Giant lipids recast the phase behavior of natural lipids to a certain degree and the abundant self‐assembled morphologies reveal distinct physiochemical behaviors when geometric parameters deviate from natural analogues.  相似文献   

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Here we report the direct comparison of a conventional batch mode synthesis of Meclinertant (SR48692, 1 ), a neurotensin receptor‐1 antagonist, with its machine‐assisted flow chemistry alternative. By using these enabling tools, combined with solid‐supported reagents and scavengers, many process advantages were observed. Care, however, must be taken not to convert these techniques into expensive solutions to problems that do not exist.  相似文献   

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