Carbohydrates carbohydrate antibiotics

Application of NMR spectroscopy to heterocyclic chemistry has developed very rapidly during the past 15 years, and the technique is now used almost as routinely as H NMR spectroscopy. There are four main areas of application of interest to the heterocyclic chemist (i) elucidation of structure, where the method can be particularly valuable for complex natural products such as alkaloids and carbohydrate antibiotics (ii) stereochemical studies, especially conformational analysis of saturated heterocyclic systems (iii) the correlation of various theoretical aspects of structure and electronic distribution with chemical shifts, coupling constants and other NMR derived parameters and (iv) the unravelling of biosynthetic pathways to natural products, where, in contrast to related studies with " C-labelled precursors, stepwise degradation of the secondary metabolite is usually unnecessary. 

Oligosaccharides also occur widely as components (via glycosidic bonds) of antibiotics derived from various sources. Figure 7.20 shows the structures of a few representative carbohydrate-containing antibiotics. Some of these antibiotics also show antitumor activity. One of the most important of this type is bleomycin A2, which is used clinically against certain tumors. 

Carbohydrate antibiotics Antibiotics that contain one or more amino sugars within the molecule are called carbohydrate antibiotics. For example, gentamicin is composed of three different units purpurosamine, 2-deoxystreptamine and garosamine. Other examples include streptomycin and neomycin. 

Carbohydrates, aminoacids, antibiotics PDMS PAD End-channel (on-chip) Gold [132]... 

Myriad natural products such as carbohydrates, ionophore antibiotics and many others possess polysubstituted oxygenated rings, such as furans, pyrans and lactone units, within their complex structure. Pyran and dihydropyran units are par-... 

Other cla.sses of therapeutically important compounds that have been. synthesized successfully by u.sing solid-pha.se combinatorial chemistry include carbohydrates and natural products. Polysaccharides ate important for various carbohydrate-protein interactions. Carbohydrate antibiotics, including vancomycin and aminoglycosides, have been the targets of combinatorial chemistry, as well as complex oligosaccharides like the one shown in Figure 3-9." A vari-... 

Pelyvas, I. F., Madi-Puskas, M., Toth, Z. G., Varga, Z., Hornyak, M., Batta, G., Szlaricskai, F. Synthesis of new pseudo-disaccharide amino glycoside antibiotics from carbohydrates. J. Antibiot. 1995, 48, 683-695. 

The anomeric effect is of prime consideration in synthetic carbohydrate chemistry in fact, some of the most important problems in this area, for example, the synthesis of oligosaccharides and carbohydrate-containing antibiotics, involve an understanding of the reactivity and properties of the anomeric center. In a detailed article concerned with the influence of reactant structure and solvent on glycoside synthesis, Schuerch explores how the anomeric effect of a number of reactants influences the course of kinetically controlled glycosidations. 

Bacterial RNA as targets of carbohydrate-based antibiotics in connection with resistance to the latter 01AG(E)3508. 

The c.i. mass spectra of carbohydrates exhibit few fragmentation pathways because of the mildness of the indirect ionization procedure, and the molecular weight can readily be obtained. This is well illustrated by the fact that such complex carbohydrate antibiotics as celesticetin (mol. wt. 528) and lincomycin (mol. wt. 406) show strikingly simple c.i. (ammonia) spectra the protonated molecular ion is the most... 

Wong C H, Bryan M C, Nyffeler P T, et al. (2003). Synthesis ot carbohydrate-based antibiotics. Pure Appl. Chem. 75 179-186. 

The synthetic challenge posed by the complex carbohydrate antibiotics was met by the total synthesis of the kanamycins in 1968, and, later, ribostamycin, butirosin B, and tobramycin were synthesized. The total synthesis of dihydrostreptomycin was accomplished by Umezawa and coworkers in 1973. 

Access to carbohydrate antibiotics by chemical assembly from their component sugars has presented exercises in synthetic virtuosity, but in general their production through microbial fermentation remains the most economically viable approach. 

An alternative approach for treating bacterial infections has seen the development of carbohydrate based antibiotics to target carbohydrate receptors and carbohydrate modifying enzymes [6]. 

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