Biological selectivity, carbohydrates

Some years ago, we started a project aimed at the development of simple and efficient enzymatic methods for the synthesis of biologically-active carbohydrates on a preparative scale. The use of enzymes as catalysts for the synthesis of carbohydrates has many potential advantages, such as enabling selective, stereo specific syntheses with a minimum of reaction steps under mild conditions and in aqueous solutions in which carbohydrates are highly soluble. Moreover, many enzymes now can be produced in quantity by fermentation and can be immobilized and reused. 

Regioselective reactions are particularly important in the synthesis of biologically interesting carbohydrates, where selective protection and deprotection of... 

Abstract To understand how membrane-active peptides (MAPs) function in vivo, it is essential to obtain structural information about them in their membrane-bound state. Most biophysical approaches rely on the use of bilayers prepared from synthetic phospholipids, i.e. artificial model membranes. A particularly successful structural method is solid-state NMR, which makes use of macroscopically oriented lipid bilayers to study selectively isotope-labelled peptides. Native biomembranes, however, have a far more complex lipid composition and a significant non-lipidic content (protein and carbohydrate). Model membranes, therefore, are not really adequate to address questions concerning for example the selectivity of these membranolytic peptides against prokaryotic vs eukaryotic cells, their varying activities against different bacterial strains, or other related biological issues. 

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... 

The selective introduction of fluorine is of continuing interest not only because of the synthetic challenge but also because of the possibility of a dramatic change in biological activity. The fluoride-ion displacement of carbohydrate trifluoromethanesulfonates using tris(dimethylamino)sulfonium... 

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