Per J. Garegg

Bio: Per J. Garegg is an academic researcher from Stockholm University. The author has contributed to research in topics: Glycosyl & Triphenylphosphine. The author has an hindex of 42, co-authored 258 publications receiving 6847 citations. Previous affiliations of Per J. Garegg include Linköping University.

Novel reagent system for converting a hydroxy-group into an iodo-group in carbohydrates with inversion of configuration. Part 2

Abstract: Isolated primary and secondary hydroxy-groups in carbohydrate derivatives are transformed into iodo-groups with inversion of configuration on treatment with either triphenylphosphine, iodine, and imidazole or triphenyl-phosphine and 2,4,5-tri-iodoimidazole at elevated temperatures. At lower temperatures, primary hydroxy-groups may be selectively replaced by iodo-groups.

Thioglycosides as glycosyl donors in oligosaccharide synthesis.

Abstract: Publisher Summary This chapter analyzes the importance of thioclycosides as the glycosyl donors in oligosaccharide synthesis. The presence and biological importance of oligosaccharide structures, usually as the components of glycolipids and glycoproteins, in bacterial capsular and cell-wall polysaccharides, in mammalian cell membranes, in cytoplasm, and in extra-cellular fluids are well documented. Acylated glycosyl thiocyanates are made by the treatment of acylated glycopyranosyl halides with potassium thiocyanate. An attractive feature of thioglycosides as the glycosyl donors in oligosaccharide synthesis is that they are readily converted into all of the other glycosyl donors. The glycosyl bromide can also be converted into a 4-pentenyl glycoside, which becomes a glycosyl donor by promotion with an iodonium compound. Tris(4-bromophenyl)ammoniurnyl hexachloroantimonate (TBPA) differs from the other promoters in the context that its cation is a radical and produces radical cationic sulfonium ions such as glycosylating species from thioglycosides. In acetonitrile as solvent, and with a nonparticipating 2-substituent in the glycosyl donor, 1,2-trans glycosides are formed as a result of solvent participant. The transfer of the Armed–Disarmed concept to thioglycoside glycosylation reactions is also elaborated in the chapter.

Thioglycosides as glycosylating agents in oligosaccharide synthesis

Abstract: A review is given of the use of thioglycosides as glycosyl donors in oligosaccharide synthesis Both indirect use, by conversion of the thioglycoside into a glycosyl halide and direct use, by electrophilic activation of the thioglycoside, are discussed

Biological Roles of Glycans

Abstract: Simple and complex carbohydrates (glycans) have long been known to play major metabolic, structural and physical roles in biological systems. Targeted microbial binding to host glycans has also been studied for decades. But such biological roles can only explain some of the remarkable complexity and organismal diversity of glycans in nature. Reviewing the subject about two decades ago, one could find very few clear-cut instances of glycan-recognition-specific biological roles of glycans that were of intrinsic value to the organism expressing them. In striking contrast there is now a profusion of examples, such that this updated review cannot be comprehensive. Instead, a historical overview is presented, broad principles outlined and a few examples cited, representing diverse types of roles, mediated by various glycan classes, in different evolutionary lineages. What remains unchanged is the fact that while all theories regarding biological roles of glycans are supported by compelling evidence, exceptions to each can be found. In retrospect, this is not surprising. Complex and diverse glycans appear to be ubiquitous to all cells in nature, and essential to all life forms. Thus, >3 billion years of evolution consistently generated organisms that use these molecules for many key biological roles, even while sometimes coopting them for minor functions. In this respect, glycans are no different from other major macromolecular building blocks of life (nucleic acids, proteins and lipids), simply more rapidly evolving and complex. It is time for the diverse functional roles of glycans to be fully incorporated into the mainstream of biological sciences.

Simple Chemical Transformation of Lignocellulosic Biomass into Furans for Fuels and Chemicals

Abstract: Lignocellulosic biomass is a plentiful and renewable resource for fuels and chemicals. Despite this potential, nearly all renewable fuels and chemicals are now produced from edible resources, such as starch, sugars, and oils; the challenges imposed by notoriously recalcitrant and heterogeneous lignocellulosic feedstocks have made their production from nonfood biomass inefficient and uneconomical. Here, we report that N,N-dimethylacetamide (DMA) containing lithium chloride (LiCl) is a privileged solvent that enables the synthesis of the renewable platform chemical 5-hydroxymethylfurfural (HMF) in a single step and unprecedented yield from untreated lignocellulosic biomass, as well as from purified cellulose, glucose, and fructose. The conversion of cellulose into HMF is unabated by the presence of other biomass components, such as lignin and protein. Mechanistic analyses reveal that loosely ion-paired halide ions in DMA−LiCl are critical for the remarkable rapidity (1−5 h) and yield (up to 92%) of this low...

Carbon-13 Nuclear Magnetic Resonance Spectroscopy of Monosaccharides

Abstract: Publisher Summary This chapter provides an overview of the 13 Carbon-nuclear magnetic resonance ( 13 C-NMR) spectroscopy of monosaccharides. The 13 C-NMR spectroscopy has become increasingly important as a tool for the characterization and structural elucidation of sugars and their derivatives. Although 13 C-NMR is closely related to 1 H-NMR spectroscopy, especially when both types of spectra are recorded with Fourier-transform instruments, the two techniques are sufficiently different to be valuable complements to each other. In many cases, in particular when dealing with complex molecules such as polysaccharides, the amount of information obtainable from 1 H-NMR spectra is limited as compared to that revealed by 13 C- NMR spectra. This chapter provides an almost complete collection of 13 C- NMR chemical shifts of monosaccharides, their methyl glycosides, and acetates, along with the examples of shift data for as many different types of monosaccharide derivative as possible. It also provides details on sampling techniques and assignment techniques, and discusses the identity of monosaccharides, their structure determination, and conformational analysis .

New Methods for the Synthesis of Glycosides and Oligosaccharides—Are There Alternatives to the Koenigs‐Knorr Method? [New Synthetic Methods (56)]

Abstract: Glycoproteins, glycolipids, and glycophospholipids (glycoconjugates) are components of membranes. The oligosaccharide residue is responsible for intercellular recognition and interaction; it acts as a receptor for proteins, hormones, and viruses and governs immune reactions. These significant activities have stimulated interest in oligosaccharides and glycoconjugates. With their help it should be possible to clarify the molecular basis of these phenomena and to derive new principles of physiological activity. Major advances in the synthesis of oligosaccharides have been made by the use of the Koenigs-Knorr method, in which glycosyl halides in the presence of heavy-metal salts are employed to transfer the glycosyl group to nucleophiles. The disadvantages of this procedure have led to an intensive search for new methods. Such methods will be discussed in this article. Emphasis is placed on glycoside and saccharide formation by 1-O-alkylation, on the trichloroacetimidate method, and on activation through the formation of glycosylsulfonium salts and glycosyl fluorides.

Applications of Continuous-Flow Photochemistry in Organic Synthesis, Material Science, and Water Treatment

Abstract: Continuous-flow photochemistry in microreactors receives a lot of attention from researchers in academia and industry as this technology provides reduced reaction times, higher selectivities, straightforward scalability, and the possibility to safely use hazardous intermediates and gaseous reactants. In this review, an up-to-date overview is given of photochemical transformations in continuous-flow reactors, including applications in organic synthesis, material science, and water treatment. In addition, the advantages of continuous-flow photochemistry are pointed out and a thorough comparison with batch processing is presented.