Asymmetric 1,3-Dipolar Cycloaddition Reactions

Introduction Cationic domino reactions Anionic domino reactions Radical domino reactions Pericyclic domino reactions Photochemically induced domino processes Transition metal catalysis Domino reactions initiated by oxidation or reduction Enzymes in domino reactions Multicomponent reactions Special techniques in domino reactions

Domino Reactions in Organic Synthesis

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.

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

Increased understanding of the important roles that oligosaccharides and glycoconjugates play in biological processes has led to a demand for significant amounts of these materials for biological, medicinal, and pharmacological studies. Therefore, tremendous effort has been made to develop new procedures for the synthesis of glycosides, whereby the main focus is often the formation of the glycosidic bonds. Accordingly, quite a few review articles have been published over the past few years on glycoside synthesis; however, most are confined to either a specific type of glycoside or a specific strategy for glycoside synthesis. In this Review, new principles for the formation of glycoside bonds are discussed. Developments, mainly in the last ten years, that have led to significant advances in oligosaccharide and glycoconjugate synthesis have been compiled and are evaluated.

New principles for glycoside-bond formation.

Anomeric-oxygen activation for glycoside synthesis: the trichloroacetimidate method.

Although Nature uses carbohydrates as synthetic precursors of many functionalized carbocyclic compounds, both saturated and aromatic, until recently chemists have paid only slight attention to the possibilities offered by this approach. It is the intention of this review to bring together the range of methods now available for producing functionalized, chiral cyclohexane and cyclopentane derivatives from sugars and to indicate how these have been applied. The progress made in recent years (>80% of the papers to appear on the subject have been published in the last decade) represents a small part of the new age of carbohydrate chemistry in which sugars have changed from being considered unmanageable to being controllable source materials for synthesis of a myriad of complex, chiral compounds. Several reviews have dealt with the use of sugars in the syntheses of natural compounds. Particular attention is drawn to a new survey which concentrates on the use of monosaccharides for the synthesis of natural products which contain carbocyclic ring systems. While it tends to deal with major features of such syntheses, the current review focuses on the chemical features of the cyclization processes. 338 refs.

The conversion of carbohydrate derivatives into functionalized cyclohexanes and cyclopentanes

A potentially versatile synthesis of glycosides

Glycals (or usually their O-substituted derivatives) are readily converted into 2,3-unsaturated glycosyl compounds with O-, C-, N-, S- or otherwise linked substituents at the anomeric position. These products have been found to be useful for a range of synthetic purposes. In particular, the C-glycosidic compounds have served as readily available starting materials for the preparation of useful non-carbohydrate compounds. While these allylic rearrangement processes are usually conducted under the influence of Lewis acid catalysts, adaptations that involve activation of the allylic substituents of the starting glycals as leaving groups under neutral conditions have been developed. General features of the reactions are described as well as applications in synthesis and extensions of the basic processes.

Substitution-with-Allylic-Rearrangement Reactions of Glycal Derivatives

Heating of the unsaturated glycoside triester (1) in refluxing aqueous acetone with mercury(II) chloride gave the cyclohexenone derivative (4) in high yield in a reaction which represents a new means of obtaining functionalised carbocyclic compounds from carbohydrates. From compound (4), the substituted cyclohexenone (5) and thence the phenol (6) were prepared.

Robert J. Ferrier

Papers

The conversion of carbohydrate derivatives into functionalized cyclohexanes and cyclopentanes

A potentially versatile synthesis of glycosides

Substitution-with-Allylic-Rearrangement Reactions of Glycal Derivatives

Unsaturated carbohydrates. Part 21. A carbocyclic ring closure of a hex-5-enopyranoside derivative

Synthesis of 1,2-trans-related 1-thioglycoside esters