Natural carbohydrate derivatives, biological

Stereoselective intramolecular oxymercuration of carbohydrate derivatives was proposed as the key reaction for efficient preparation of mono- and dihydroxylated unsymmetrical bis-tetrahydrofuran skeletons present in naturally occurring biologically active acetogenins. The trans- and. mz-selective intramolecular oxymercurations were explored in an enantioselective synthesis of the bis-tetrahydrofuran skeleton of mucoxin (Fig. 57).73... 

Contents B. FRASER-REID and R. C. ANDERSON, Carbohydrate Derivatives in the Asymmetric Synthesis of Natural Products — H. JONES and G. H. RASMUSSON, Recent Advances in the Biology and Chemistry of Vitamin D — S. LIAAEN-JENSEN, Stereochemistry of Naturally Occurring Carotenoids — T. KASAI and P. O. LARSEN, Chemistry and Biochemistry of y -Glutamyl Derivatives from Plants Including Mushrooms (Basidiomycetes) - Author Index - Subject Index. 

Carbohydrate derivatives found in nature are almost always linked to each other by glycosidic bonds. There has been increasing interest in the synthesis of biologically active ohgo- and polysaccharides and reliable methods for the formation of gjyco-sidic linkages have been the subject of intensive study. 

The widespread occurrence and biological significance of polyoxygenated carbocycles provided the impetus to apply RCM to sugar-derived dienes. Carbohydrate carbocyclization based on a sequence of Vasella reductive opening of iodo-substituted methyl glycosides [25], and RCM of the dienes available from the resulting unsaturated aldehydes, were used to prepare a series of natural compounds (Schemes 5-7). 

First, the above-mentioned sensors have major drawbacks, as the detection and recognition event is a function of the nature and characteristics of the side chains, and the side chain functionalization of the CP requires advanced synthesis and extensive purification of numerous monomeric and polymeric derivatives. Second, this generation of sensors primarily employed optical absorption as the source for detection, resulting in lower sensitivity when compared with other sensing systems for biological processes. However, the use of fluorescence detection within these sensing systems could justify continued development. More recent examples include a fluorescent polythiophene derivative with carbohydrate functionalized side chains for the detection of different bacteria [15] and novel synthesis schemes for ligand-functionalization of polythiophenes [16]. 

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