Advances In Synthetic Methodologies Research Articles

Controlled Synthesis of Monodisperse Magnetic Nanoparticles in Solution Phase

Magnetic nanoparticles (NPs) show interesting size/shape-dependent magnetism and magnetic transition from ferromagnetism to superparamagnetism. Such unique nanomagnetism has been studied extensively in the hope to optimize magnetic NPs for future magnetic data storage, energy storage and biomedicine applications. To achieve any of these application goals, the size, composition, shape and surface structure of these NPs must be first controlled so that their magnetic properties can be tuned for specific applications. Recent advances in synthetic methodology have led to the formation of various magnetic NPs with the desired dimension controls. This review focuses on solution phase based chemical syntheses of monodisperse magnetic NPs. It starts with a brief introduction of nanomagnetism and a general overview of colloid chemistry in the synthesis of monodisperse NPs. It further illustrates several typical examples on chemical syntheses of Fe, Co, FePt, CoFe and iron oxide NPs. The review concludes with the challenges and future perspective in magnetic NP synthesis and applications.

Click Chemistry with Polymers, Dendrimers, and Hydrogels for Drug Delivery

During the last decades, great efforts have been devoted to design polymers for reducing the toxicity, increasing the absorption, and improving the release profile of drugs. Advantage has been also taken from the inherent multivalency of polymers and dendrimers for the incorporation of diverse functional molecules of interest in targeting and diagnosis. In addition, polymeric hydrogels with the ability to encapsulate drugs and cells have been developed for drug delivery and tissue engineering applications. In the long road to this successful story, pharmaceutical sciences have been accompanied by parallel advances in synthetic methodologies allowing the preparation of precise polymeric materials with enhanced properties. In this context, the introduction of the click concept by Sharpless and coworkers in 2001 focusing the attention on modularity and orthogonality has greatly benefited polymer synthesis, an area where reaction efficiency and product purity are significantly challenged. The purpose of this Expert Review is to discuss the impact of click chemistry in the preparation and functionalization of polymers, dendrimers, and hydrogels of interest in drug delivery.

Total synthesis of palau'amine.

Total synthesis of palau'amine.

Development of Novel Conjugated Donor Polymers for High-Efficiency Bulk-Heterojunction Photovoltaic Devices

Solar cells are one attractive method for harnessing inexhaustible clean energy from the sun. Organic photovoltaic technology is emerging as a potential competitor to silicon-based photovoltaic cells (PVCs), and their power conversion efficiencies (PCE) can now exceed 6%. Polymeric bulk-heterojunction (BHJ) PVCs, whose photoactive layer is composed of a blend of bicontinuous and interpenetrating donors and acceptors, can maximize interfacial area between the donor and the acceptor. Classic polymer donors, such as dialkoxy-substituted poly(para-phenylene vinylene)s (PPVs) and poly(3-hexylthiophene) (P3HT), have been widely investigated. However, advances in synthetic methodology provide new avenues for the development of novel conjugated polymer donors with improved power conversion efficiencies. Recently, researchers have achieved great advances in this area. This Account primarily focuses on novel donor polymers that have shown power conversion efficiencies greater than 1%. 2,1,3-Benzothiadiazole, thiophene, thieno[3,4-b]pyrazine, quinoxaline, and silole have emerged as useful heterocycles for constructing a variety of conjugated polymers for photovoltaic applications. We summarize useful information, such as molecular weights, absorption, bandgap, energy levels, and their photovoltaic performances with detailed device parameters (see comparison tables), about these novel donor polymers. We use statistical summaries to evaluate several important parameter relationships among these polymer donors including open-circuit voltage versus HOMO, power conversion efficiency versus bandgap, and power conversion efficiency versus hole mobility. Further statistical analysis of the data listed in these tables may guide further structural design and evaluation of polymer donor materials.

Pattern Recognition in Retrosynthetic Analysis: Snapshots in Total Synthesis.

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Pattern Recognition in Retrosynthetic Analysis: Snapshots in Total Synthesis

In this Perspective, the value of small molecule natural products (SMNPs) in the discovery of active biological agents is discussed. The usefulness of the natural products-based method of potential pharma discovery is much augmented by the capacities of chemical synthesis. The great advances in synthetic methodology allow for major editing of the natural product in the hopes of optimizing potency and therapeutic index. As a consequence of the enormous increase in the power of multistep chemical synthesis, one can now approach structures of previously impractical complexity. In constructing a plan for a multistep synthesis, two complementary thought styles are often encountered. One is the traditional and extremely powerful concept of prioritized strategic bond disconnections. The other, which we term "pattern recognition," involves the identification of moieties within the target, which are associated with reliable chemistry, and can serve to facilitate progress to the target. Recognition of such targets may require substantial recasting of the target structure to connect it to well-established types of transformations. Some of our older ventures, where ideas about pattern recognition were first being fashioned and used productively, are revisited. In addition, we provide snapshots of recently achieved total syntheses of SMNPs of novel biological potential. These vignettes serve to harmonize insights occasioned by pattern recognition, in concert with transformations enabled by the enormous growth in the power of synthesis.

Preparation and Evaluation of Unimolecular Pentavalent and Hexavalent Antigenic Constructs Targeting Prostate and Breast Cancer: A Synthetic Route to Anticancer Vaccine Candidates

Several novel, fully synthetic, carbohydrate-based antitumor vaccines have been assembled. Each construct consists of multiple cancer-related antigens displayed on a single polypeptide backbone. Recent advances in synthetic methodology have allowed for the incorporation of a complex oligosaccharide terminating in a sialic acid residue (i.e., GM2) as one of the carbohydrate antigens. Details of the vaccine synthesis as well as the results of preliminary immunological investigations are described herein.

Preface

_ The most easterly point of North America was the setting for the 11th International Symposium on Novel Aromatic Compounds (ISNA-11), which took place on 14-18 August 2005 in the picturesque harbor city of St. John's, Newfoundland and Labrador, Canada. An atypically small, but nevertheless enthusiastic, group of 135 delegates representing 17 countries and 64 academic and industrial institutions participated in ISNA-11. The scientific program consisted of 107 posters (two sessions), 26 plenary lectures, and the Nozoe lecture, which was presented by Prof. Koichi Komatsu of Kyoto University.The inaugural ISNA meeting was held in Sendai, Japan in 1970. Since then, ISNA meetings have been held at three- to four-year intervals at locations that cycle between Asia, North America, and Europe. In its infancy, the ISNA community was focused primarily on the definition and quantification of aromaticity, as well as the synthesis and study of compounds that exhibited the phenomenon, whatever it may be. Nourished by advances in synthetic methodology, analytical techniques, separation capabilities, and computational power, ISNA has blossomed over the intervening 35 years to embody a much broader and deeper set of interests. In particular, the twin issues of function and applications have emerged as integral components of ISNA's collective being.The scientific topics of ISNA-11 were selected with an eye toward balancing the traditional areas of interest with its expansion in new directions. The 15 articles that appear in this issue embody these themes, which include:the synthesis of aromatic compoundstheoretically interesting aromatic moleculesstructural aspects of aromaticityaromatic compounds for devicesfullerenes and nanotubesmolecular switches and machinesmacrocyclic aromatic compoundsDebate about the status and future direction of ISNA was actively encouraged, and the overwhelming response was that ISNA is more vibrant and relevant than ever before. It is healthy and growing in many ways. It was therefore decided to move subsequent ISNA meetings to a two-year cycle. This will commence with ISNA-12, which will be held on Awaji Island (located near Kobe) in Japan on 22-27 July 2007. Professor Yoshito Tobe (Osaka University) will serve as conference chair. The responsibility for ISNA-13 was also awarded. It will be organized by Prof. François Diederich (ETH Zürich) and will be held at a yet to be determined European location in 2009.Graham BodwellRik TykwinskiConference Editors

Isosteric replacement of sulfur with other chalcogens in peptides and proteins

The review addresses the functional and structural properties of the two series of chalcogen analogues of amino acids in peptides and proteins, the methionine and the serine/cysteine series, and discusses the synthesis of the related selenium/tellurium analogues as well as their use in peptide synthesis and protein expression. Advances in synthetic methodologies and recombinant technologies and their combined applications in native and expressed protein ligation allows the isomorphous character of selenium- and tellurium-containing amino acids to be exploited for production of heavy metal mutants of proteins and thus to facilitate the phasing problem in x-ray crystallography. In addition, selenocysteine has been recognized as an ideal tool for the production of selenoenzymes with new catalytic activities. Moreover, the fully isomorphous character of disulfide replacement with diselenide is well suited to increase the robustness of cystine frameworks in cystine-rich peptides and proteins and for the de novo design of even non-native cystine frameworks by exploiting the highly negative redox potential of selenols.

Dendritic polymers composed of glycerol and succinic acid: Synthetic methodologies and medical applications

Abstract Research on dendrimers continues to expand as further advances in synthetic methodology and characterization techniques translate to additional applications. Recently, dendritic polymers composed of the natural metabolites glycerol and succinic acid were synthesized, functionalized, and evaluated as new medical materials. The design and synthesis of poly(glycerol-succinic acid) dendritic polymers are discussed, including comparing and contrasting the convergent versus the divergent methodologies for preparing such macromolecules. Finally, a photocrosslinkable dendritic macromolecule was prepared and successfully used to close linear corneal lacerations as well as to secure LASIK flaps.

ChemInform Abstract: The Continuing Magic of Benzotriazole: An Overview of Some Recent Advances in Synthetic Methodology

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The continuing magic of benzotriazole: An overview of some recent advances in synthetic methodology

The continuing magic of benzotriazole: An overview of some recent advances in synthetic methodology