Glycopeptide treatment

Glycopeptides. — Treatment with sodium in liquid ammonia has been used as a novel method of benzyl- and benzylidene-group deprotection in glycopeptide synthesis. ... 

Removal of the oligosaccharide chain from the glycoprotein usually involves the use of one of three main methods treatment with NaOH-NaBH4, hydrazinolysis, or proteolysis.34-36 The NaOH-NaBH4 treatment is used to release, somewhat specifically, oligosaccharides O-linked to serine and threonine. Hydrazinolysis is used to break N-linkages, and proteolysis, to isolate glycopeptides. Each method apparently still has some drawbacks. 

Garg and Jeanloz85,129 131 made extensive use of this procedure in order to obtain L-serine-containing mono-, di-, and tri-glycopeptide derivatives of 2-amino-2-deoxy-D-glucose. Thus, treatment of 6 with the... 

With respect to application of MS to deprotection reactions, Mizuno et al.105 observed an unexpected O-acetyl cleavage in a building block of an N-glycopeptide by simple treatment with absolute methanol that had been stored over 3 A MS. When acetates from other sugars were submitted to the same conditions, similar results were obtained, whereas no O-acetyl cleavage was observed when using absolute methanol that had not been dried over 3 A MS. This deacetylation was evidently promoted by a... 

The detachment of the glycopeptide from the resin and deprotection of the amino acid side chains as well as the removal of the acid-labile carbohydrate protecting groups were simultaneously carried out using TFA/H20/thioanisole/ethanedithiol (87.5 5 5 2.5). This treatment proceeded without affecting the glycosidic bonds and furnished the target molecule 38. 

The four glycopeptides were detached from the resin by treatment with... 

A hexaglycine spacer was attached to the solid support to give a substitution of 0.2 mmol g of dry silica and the excess amino groups were then capped using acetic anhydride. In the next step a selectively cleavable, a-chymotrypsin sensitive, phenylalanine ester (2) was implemented for the release of the products from the solid support under mild conditions. Subsequently it was transformed to (3) followed by reactions with glycosyl transferases to yield (4). Finally, the desired glycopeptide was cleaved from the solid support in high yield by treatment of (4) with a-chymotrypsin (Scheme 10.1). 

Tertiary treatment implemented Genes encoding D-alanine D-alanine ligases with a broad substrate specificity confer inducible resistance to the glycopeptides antibiotics, as vancomycin World Health Organization Wild-type... 

Other inhibitors of cell wall synthesis. Bacitracin and vancomycin interfere with the transport of pepti-doglycans through the cytoplasmic membrane and are active only against gram-positive bacteria. Bacitracin is a polypeptide mixture, markedly nephrotoxic and used only topically. Vancomycin is a glycopeptide and the drug of choice for the (oral) treatment of bowel inflammations occurring as a complication of antibiotic therapy (pseudomembranous enterocolitis caused by Clostridium difficile), it is not absorbed. 

Vancomycin (40) [85] is a glycopeptide antibiotic that is widely used in the treatment of Gram-positive bacterial infections (Fig. 19). It was discovered in a soil sample from the jungles of Borneo during a research program carried out by the pharmaceutical company Eli Lilly in the mid-1950s. Streptomyces orientalis (later... 

---