Current Organic Chemistry - Volume 18, Issue 13, 2014

Methodologies for the synthesis of polyhydroxylated carbocyclic derivatives with medium (7- and 8-member) rings are reviewed. Polyhydroxylated carbocyclic derivatives with larger rings are practically unknown; only few examples can be found in the literature. This review is focused on the methods of preparation rather than on the size of cyclitols. Various types of compounds with medium carbocyclic rings are discussed. Selected examples of polyhydroxylated derivatives with very large rings, containing also heteroatoms in the cyclic framework, are also reported.

Carbohydrates have been utilized as starting materials for the synthesis of pyranopyrans, which are important building blocks for the total synthesis of polyethers and other natural products. This review focuses on the synthesis of pyranopyrans from carbohydrates, with emphasis on the stereoselective functionalization of sugars and on the methods used to construct additional rings onto a carbohydrate template. Anhydro sugars, deoxy sugars, lactones, glycals, glycosides and other derivatives of carbohydrates have been used as starting materials for the synthesis of natural products such as ansamycins, halichondrin B, okadaic acid, dactomelynes, thyrsiferol, and polyethers brevetoxin A, ciguatoxin, and brevisin. Methods for ring closure are covered and show a progression toward the increased use of metal-catalyzed processes.

Carbapyranoses, i.e., pyranose derivatives whose ring oxygen has been replaced by a methylene group, are currently recognized as valuable carbohydrate mimetics. A plethora of methods are available for their preparation, and among them the radical cyclization of suitably functionalized carbohydrate derivatives has already positioned itself as a reliable synthetic method. The present review aims to give an overview of the different synthetic strategies based on radical cyclization that have been employed in their preparation. Recent contributions from our research group are included, which will serve to delineate the scope and limitations of these methods.

This review provides a comprehensive compilation of available literature concerning the synthesis and applications of cyclic nitrones derived from sugars and hydroxyacids. The most important recent developments and concepts related to this topic are emphasized.

Recent advances in stereocontrolled Wittig olefination of sugars with stabilized and semi-stabilized phosphoranes are reviewed. Transformations of free and protected sugars for chain elongation at both reducing and terminal ends, and branched chain construction at the carbon atoms 2, 3 and 5 demonstrate the usefulness of this reaction in the preparation of a number of biologically active molecules and their precursors, starting from readily available sugars. Higher sugars, bicyclic structures, and C-C linked oligosaccharides lie amongst the diversity of compounds shown in this review that are synthesized by this reaction, easily carried out and efficient in terms of reaction yield and stereoselectivity, depending on reagents and reaction conditions. The analogy of aza-Wittig reaction, based on reaction of N-alkyl-triphenyl-λ5-phosphanimines with aldehydes or ketones, encouraged us to consider its contribution for the synthesis of N-linked sugars and imino sugars, which have biological and - some of them - industrial application as inhibitors of glycoprocessing enzymes. The use of this reaction for the preparation of pseudonucleosides with the N-linked appendages, N-linked and thiazolidinone-linked saccharides, and a diversity of imino sugars will be highlighted and the reaction stereocontrol discussed.

This review describes the applications of carbohydrate-derived ligands in enantioselective transition metal catalysis since 2008 year. The areas of hydrogenation with molecular hydrogen and transfer hydrogenation, allylic substitution, 1,4-conjugate addition, epoxidation, cyclopropanation and addition to carbon-heteroatom double bonds are covered.

Chemical reactions using isomaltulose as the starting material leading to advanced functional carbohydrate derivatives are reviewed. A focus is made notably on the synthesis and application of different kinds of carboxylic acids and lactones obtained by oxidation of isomaltulose and the strategies using its triply dehydrated derivative, glycosyloxymethylfurfural.

The increased appreciation of the role of carbohydrates in the biological sciences has resulted in a multidisciplinary interest in carbohydrate chemistry. The widespread use of these materials is due to both their availability as well as the need for green and renewable bio-based materials. Moreover, sugar-containing synthetic polymers are being increasingly investigated as biodegradable, biocompatible and biorenewable materials. Among the carbohydrates, sucrose, produced from renewable sources, is the most abundant sugar, but only a small percentage of its production is used as a chemical reagent. However, one major drawback for the direct use of sucrose for industrial processes is its polyfunctionality. Consequently, the control of chemoselectivity is a major challenge in the development of its potential applications. This article reviews the recent trends in the chemoselective synthesis of sucrose building blocks and the synthesis and characterization of synthetic sucrose-based polymeric materials