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The in situ-generated thiocarbonyl S-methanides derived from cycloaliphatic thioketones undergo (3+2) cycloaddition onto the C=C bond of levoglucosenone yielding anticipated, polycyclic tetrahydrothiophene derivatives in a regio- and stereoselective manner. The cycloaddition process occurred stereoselectively via the less hindered exo-face approach; exo-diastereoisomers were formed in all studied reactions. Some of the obtained crystalline (3+2) cycloadducts were studied by the monocrystal X-ray diffraction analysis, which unambiguously confirmed the postulated structure. Stable (3+2) cycloadducts were isolated in good yields (50-80%).

Heterocyclic sulfur and nitrogen containing compounds capable of forming an equilibrium: thiol/imine = thione/amine (N=C-S-H ⇌ H-N-C=S) were reacted with levoglucosenone (LG) in the presence of triethylamine. Unexpectedly, the only isolated products were the result of the aza-Michael addition. No S-adducts were detected. All products were crystalline with good to excellent yields. The structure of products was determined using NMR, MS, and single-crystal X-ray analysis.

The in situ-generated N-aryl nitrile imines derived from trifluoroacetonitrile smoothly undergo (3+2)-cycloadditions onto the enone fragment of the levoglucosenone molecule, yielding the corresponding, five-membered cycloadducts. In contrast to the ‘classic’ C(Ph),N(Ph) nitrile imine, reactions with fluorinated C(CF3),N(Ar) analogues lead to stable pyrazolines in a chemo- and stereoselective manner. Based on the result of X-ray single crystal diffraction analysis, their structures were established as exo-cycloadducts with the location of the N-Ar terminus of the 1,3-dipole at the α-position of the enone moiety. The DFT computation demonstrated that the observed reaction pathway results from the strong dominance of kinetic control over thermodynamic control.

Levoglucosenone (LGO) smoothly undergoes microwave-assisted hetero-Diels–Alder reactions with thiochalcones in THF solution at 60 °C. The studied reactions are completed after 10 min, and the expected tricyclic 2,3-dihydro-4H-thiopyran derivatives are formed in a highly regio- and moderately stereoselective manner via competitive exo- and endo-attacks of the 1-thiadiene moiety onto the activated C=C bond of dienophile LGO. Although eight isomers are possible, only the formation of exo,exo- (major) and exo,endo- (minor) cycloadducts was observed. In most cases, isomeric products were separated by preparative layer chromatography and identified by means of spectroscopic methods. Some of the cycloadducts were obtained as single crystalline solids, and X-ray analyses enabled unambiguous confirmation of their structures. In order to explain the observed selectivity of the studied hetero-Diels–Alder reactions, DFT studies were carried out to determine the thermodynamic and kinetic properties of all regio- and stereoisomers. The results of these calculations predict the preferred formation of the two experimentally observed isomers. In addition, remarkable details on the electronic structure of E-1,3-diphenylprop-2-en-1-thione and on involved and hypothetical transition states could be elucidated.

Lays the foundation for new methods and applications of carbohydrate click chemistry Introduced by K. Barry Sharpless of The Scripps Research Institute in 2001, click chemistry mimics nature, giving researchers the tools needed to generate new substances quickly and reliably by joining small units together. With contributions from more than thirty pioneering researchers in the field, this text explores the many promising applications of click chemistry in glycoscience. Readers will learn both the basic concepts of carbohydrate click chemistry as well as its many biomedical applications, including synthetic antigens, analogs of cell-surface receptors, immobilized enzymes, targeted drug delivery systems, and multivalent cancer vaccines. Click Chemistry in Glycoscience examines a broad range of methodologies and strategies that have emerged from this rapidly evolving field. Each chapter describes new approaches, ideas, consequences, and applications resulting from the introduction of click processes. Divided into four sections, the book covers: Click chemistry strategies and decoupling Thio-click chemistry of carbohydrates Carbohydrate click chemistry for novel synthetic targets Carbohydrate click chemistry in biomedical sciences Thoroughly researched, the book reflects the most recent findings published in the literature. Diagrams and figures throughout the book enable readers to more easily grasp complex concepts and reaction processes. At the end of each chapter, references lead to the primary literature for further investigation of individual topics. The application of click chemistry to carbohydrates has tremendous implications for research. With this book as their guide, researchers have a solid foundation from which they can develop new methods and applications of carbohydrate click chemistry, including new carbohydrate-based therapeutics.

Thiosugars, containing a sulfur atom as heteroatom or a disaccharide linked via a sulfur bridge, possess unique physicochemical properties such as water solubility, which differs from conventional functionalized monosaccharides. The differences in biological activities between thiosugars and their oxygen analogs depend on geometric, conformational, and flexibility differences. They depend also on their electronic differences, the sulfide function being less electronegative and more polarizable than the ethereal moiety. Many functionalized thiosugars occur naturally and are potential targets for the development of carbohydrate-based therapeutics. Among the few new examples of the potential new targets are salacinol and kotalanol, tagetitoxin, thiolactomycin and analogues, mycothiol and analogues, and S-nitrosothiols. These new developments and representative examples of functionalized thiosugar prototypes as potential new targets are presented in this mini review.[PUBLICATION ABSTRACT]

The book consists of a brief introduction, a foreward provided by professor Danishefsky of Columbia University, and about 14 - 16 chapters, each written by one or two eminent scholars/authors describing their recent research in the area of either domino reactions or intramolecular rearrangements in carbohydrate chemistry. Three or four chapters will be reviews. The domino (cascade, tandem) reactions are always intramolecular. They are usually very fast, clean and offer highly complex structures in a one pot process. Intramolecular rearrangements offer very similar advantages and often lead to highly complex products as well. Although many recently isolated carbohydrates fulfill various sophisticated functions, their structures are often very complex. The editors cover the broadest scope of novel methodologies possible. All the synthetic and application aspects of domino/cascade reactions are explored in this book. A second theme that will be covered is intramolecular rearrangement, which is also fast, stereoselective, and often constitutes one or more steps of domino / cascade process. Selected examples of intramolecular rearrangements are presented. Together, both processes offer an elegant and convenient approach to the synthesis of many complex molecules, which are normally difficult to synthesize via alternative routes. It appears that domino and intramolecular rearrangements are ideally suited to synthesize certain specific modified monosaccharides. What is particularly important is that both processes are intermolecular and almost always yield products with very well-defined stereochemistry. This high definition is absolutely crucial when synthesizing advanced, modified mono and oligosaccharides. The choice of contributors reflects an emphasis on both therapeutic and pharmacological aspects of carbohydrate chemistry.

The conjugate N-adducts of thio-1,3,4-diazole and 2-thiazoline with levoglucosenone were synthesized via a stereoselective, base-catalyzed conjugate N-Michael addition to levoglucosenone at C-4. Structural assignments were established using 1H and 13C NMR analysis, and X-ray single-crystal analysis for one of the compounds. The biological properties of the novel compounds were tested on a cell model. Cytotoxicity was analyzed via colorimetric assay. Two distinct types of cell death, apoptosis and necrosis, were analyzed by determining the phosphatidylserine levels from the outer leaflet of the plasma membrane, caspase activation, and lactate dehydrogenase release. We also evaluated DNA damage using an alkaline comet assay. The level of oxidative stress was measured with a modified comet assay and an H2DCFDA probe. The thio-1,3,4-diazole adduct (FCP23) and the 2-thiazoline adduct (FCP26) exhibit similar cytotoxicity values for cancer cells (ovarian (A2780), breast (MCF-7), cervix (HeLa), colon (LoVo), and brain (MO59J and MO59K)), but their mechanism of action is drastically different. While FCP23 induces oxidative stress, DNA damage, and necrosis, FCP26 induces apoptosis through caspase activation.

Sugars with heteroatoms other than oxygen have attained considerable importance in glycobiology and in drug design since they are often more stable in blood plasma due to their resistance to enzymes, such as glycosidases, phosphorylases and glycosyltransferases. The replacement of oxygen atoms in sugars with sulfur forms thio-sugars, which are potentially useful for the treatment of diabetes and some bacterial and viral infections. Here, we evaluated the antibacterial activity of thio-functionalized carbohydrate derivatives. A set of 21 compounds was screened against acid-fast Mycobacterium tuberculosis (Mtb), gram-negative Escherichia coli and gram-positive Staphylococcus aureus. The tested carbohydrate derivatives were most effective against tubercle bacilli, with as many as five compounds (thioglycoside 6, thiosemicarbazone 16A, thiosemicarbazone 20, aminothiadiazole 23, and thiazoline 26) inhibiting its growth with MIC50 ≤ 50 µM/CFU. Only two compounds (aminothiadiazole 23 and thiazoline 26) were able to inhibit the growth of E. coli at concentrations below 1 mM, and one of them, aminothiadiazole 23, inhibited the growth of S. aureus at a concentration ≤1 mM. The five compounds affecting the growth of mycobacteria were either thiodisaccharides (6, 16A, and 20) or thioglycosides (23 and 26). All of these compounds (6, 16A, 20, 23, and 26) were able to inhibit the growth of Mtb deposited within human macrophages. However, three of the five selected compounds (6, 23, and 26) exhibited relatively high cytotoxicity in mouse fibroblasts at micromolar concentrations. The selected thio-sugars are very promising compounds, thus making them candidates for further modifications that would decrease their cytotoxicity against eukaryotic cells without affecting their antimycobacterial potential.

The comprehensive guide to the current understanding of galectins and their promising potential in drug design This is the first book focusing on galectins. It was inspired by topics discussed at the symposium \"Galectins: Structures, Functions, and Therapeutic Targets\" that was a part of the 234th American Chemical Society meeting in 2007. To help chemists, biochemists, and others understand the challenges inherent in the study of galectins and build on recent advances in the field, the editors have compiled articles from leading experts on galectins and their biomedical applications. Galectins includes: * An overview of early galectin research * An explanation of the nature of galectins * A discussion of the structure and functions of galectins, their ligand specificity and molecular mechanisms of action, and the localization of galectins in the cell * An exploration of the roles galectins play in tumor growth and cancer, fibrosis, inflammation, and immunity * A discussion of the effect of galectins on cell migration, angiogenesis, and chemoresistance * An introduction to new approaches to designing galectin inhibitors This is the premier reference on galectins for organic, medicinal, carbohydrate, and pharmaceutical chemists, biochemists, molecular and cell biologists, pharmacologists, cancer researchers, and graduate-level students in these disciplines, as well as clinicians and drug developers.