Abstracts


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Recent Applications of Click Chemistry for the Synthesis of Radiotracers for Molecular Imaging
Constantin Mamat, Theres Ramenda and Frank R. Wuest

Click chemistry has received considerable attention as powerful modular synthesis approach, which has found numerous applications in many areas of modern organic chemistry, drug discovery and material science. Recently, click chemistry, and in particular the copper-mediated 1,3-dipolar [3+2] cycloaddition between azides and alkynes, has also entered the field of radiopharmaceutical sciences. This review addresses the recent developments of click chemistry for the synthesis of various radiotracers for molecular imaging purposes. Click chemistry-based radiotracers that will be covered include peptides and small organic molecules containing the short-lived positron emitter fluorine-18, and the gamma-emitters technetium-99m, indium-111, and iodine-125.


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Asymmetric vinylogous Mukaiyama aldol reactions using vinylketene N,O-acetals in total syntheses of natural products
Seijiro Hosokawa and Kuniaki Tatsuta

Asymmetric vinylogous aldol reaction is a powerful methodology to introduce a multi functional group in the stereoselective manner. Recently, we have developed highly stereoselective vinylogous Mukaiyama aldol reactions using vinylketene N,O-acetals possessing the chiral oxazolidone. Our methodology has been applied to the asymmetric syntheses of natural products to establish the short and efficient routes. This review focuses on the asymmetric vinylogous Mukaiyama aldol reactions using vinylketene N,O-acetals in total syntheses of natural products.


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Hydrocarbon Oxygenations with Peroxides Catalyzed by Metal Compounds
Georgiy B. Shul’pin

Recent works devoted to the oxygenations of saturated, aromatic as well as olefinic hydrocarbons are surveyed, and the emphasis is made on the author’s own publications. Both soluble metal complexes and solid metal compounds catalyze oxidative transformations of hydrocarbons. Hydrogen peroxide, alkyl peroxides, and peroxy acids were used in these reactions as oxidants. The catalytic systems often include obligatory co-catalysts, for example, nitrogen-containing bases or acids (inorganic, carboxylic or amino acids).


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Recent applications of phosphinite POCOP pincer complexes towards organic transformations
David Morales-Morales

Pincer complexes have represented a group of very important species in organometallic chemistry in the last decade. Among these, phosphinite POCOP pincer complexes have recently been used profusely in metal mediated organic transformations due to the easiness on their synthesis, high thermal stability and enhanced catalytic activity. This minireview presents the evolution and recent advances in the chemistry and applications of this important group of compounds in different cross coupling reactions and other transformations relevant in organic synthesis.


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Recent advances in positron emission tomography (PET) imaging of biomolecules: From chemical labeling to cancer diagnostics
Katsunori Tanaka and Koichi Fukase

The recent advances of PET using biomolecules, such as peptides, monoclonal antibodies, oligonucleotides, and glycoproteins will be described. So far, PET of biomolecules has been used mainly for diagnosis of cancers. The biomolecules have been conjugated with DOTA ligand, labeled with radiometals as the ß+ emitter, and targeted to specific tumors, where they have enabled visualization of even small metastatic lesions, due to the high sensitivity of the PET scanners.


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Recent developments in 5 '-terminal cap analogs: Synthesis and biological ramifications
Anilkumar R. Kore, Irudaya Charles, Muthian Shanmugasundaram, Zejun Xiao and Richard C. Conrad

The 5'-terminus of eukaryotic messenger RNA (mRNA) molecules contains a unique ‘cap’ structure: 7-methylguanosine (m⁷G) linked by a 5'-5'-triphosphate bridge to the first nucleoside in the standard polymer chain. This 5'-cap is recognized by numerous enzymes involved in the transport and translation of mRNA, as well as its processing, both in terms of generating mature mRNA from the initial transcript and its natural degradation. In vitro generation of capped RNAs uses a cap analog in which two nucleosides are joined in a 5'-5' triphosphate linkage, allowing incorporation of the cap along with the first nucleotide in the polymer chain. The conventional cap analog, m⁷G[5']ppp[5']G, has a 3'-OH on both nucleoside moieties, resulting in the incorporation of the dinucleotide in either orientation. This results in one-third to one-half of the mRNAs containing a non-methylated cap and a methylated initial nucleotide. These ‘reverse cap’ structures bind poorly to elF4E and other cap binding proteins, greatly reducing the overall translational efficiency in vitro and biological activity in vivo. This drawback of the conventional cap analog has been addressed by creating an "anti-reverse cap analog" (ARCA), m₂⁷,³'-OG[5']ppp[5']G, in which the 3'-OH of the ribose connected to the m⁷Guo moiety is replaced with a 3'-O-methyl group, allowing incorporation only in the forward orientation due to the presence of the single extendable 3'-OH group. In addition to the chemical modification at the 3'-OH group of the ribose connected to the m⁷G moiety, modifications at the 2'-OH group also preclude attachment of a second nucleotide by polymerase, again forcing the forward orientation. This mini-review focuses on recent developments in the synthesis of novel cap analogs, highlighting modifications at several positions including; the heterocyclic bases, the sugars, and the a-, β-, and γ-phosphates in the triphosphate chain, and assessing their impact on biological activity.


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Microwave-assisted Claisen and aza-Claisen rearrangements
Dmytro O. Tymoshenko

This review covers the key advances in the study of Claisen rearrangement under microwave irradiation conditions. It surveys [3,3] sigmatropic rearrangements of vinyl allyl ethers, aryl allyl ethers, ortho-ester and aza Claisen rearrangements. Applications of the method for the synthesis of heterocyclic and natural compounds are surveyed.


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Recent advances in free radical chemistry of C-C bond formation in aqueous media: From mechanistic origins to applications
V.T. Perchyonok and I.N. Lykakis

Recent advances in free radical chemistry have expanded the versatility and flexibility of carbon-carbon bond formation in water or aqueous media. This review highlights the substantial progress, which has been made in the last decade to “tame” the reactive free radical species in aqueous phase reactions. This review focused on recent advances in several classes of widely useful free radical reactions in water leading to the formation of C-C bonds. The review will also explore the recent advances in performing stereo-selective free radical reactions in an aqueous medium and its application in synthesis of natural and unnatural amino acids, preparation of novel materials and solid support chemistry. Some practical hints for help design high yielding free radical reactions in aqueous medium are also presented.


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Recent Advances on Cyclopeptide-Based Glycoclusters
Olivier Renaudet

Many important biological processes including fertilization, tissue formation, cell adhesion, antigen/antibody interactions, cancer metastasis or pathogen infection involve polyvalent interactions between oligomeric proteins and carbohydrate-based ligands. The synthesis of multitopic, molecularly-defined structures that display both clustered sugars and immobilization or bioactive agents represents an attractive approach for the discovery of new diagnostics and therapeutics. This mini-review updates the current developments in this field by focusing on the recent interests on cyclopeptide-based glycoclusters.