Carbohydrate, numbering system

The scope of this cycloaddition reaction was very promising. Subsequently, removal of the CC-double bond and stereoselective functionalizations at positions 4 and 5 (carbohydrate numbering) was investigated for the synthesis of carbohydrates and related natural products, to provide C-3 branched carbohydrate derivatives (or C-4 heteroatom substituted derivatives after carbon/he-teroatom exchange reactions). However, the desired hydrogenation of such systems with various hydrogen donors has mainly resulted in low yields and/or side reactions due to the inherent stability of the formal CC-double bond (12., 15). ... 

Two numbering systems are used in this review. According to the first, which is based on the nomenclature of heterocyclic systems, the anomeric carbon atom is denoted as C(2) (number in parentheses). If carbohydrate convention is applied, this carbon atom becomes Cl, and the number is not in parentheses. 

Figure 2 Carbohydrate and Ether Appendage Numbering System (a) 2,3,6-Tri-O-methylcellulose Repeat Unit, 2 (b) 2,3,6-Tri-O-allylcellulose Repeat Unit, 3 (c) 2,3,6-Tri-O-crotylcellulose Repeat Unit, 4 (d) 6-Phenyl-6-deoxy-2,3-di-0-methyl-cellulose Repeat Unit, 9...

Fig. 4.9. Sequences in the Ch regions of human y chains (four subclasses) and of the rabbit y chain. The numbering system of protein Eu (IgGl) is used (2). References for human IgGl (y,) are 2, 59, 78, and 92 for IgG2 (y ) 79, 89, 90, and 168 IgG3 (yi) 80, 167, and 168 IgG4 (74) 88 and 167 rabbit IgG 71, 61-63, 169. The symbols L or H adjacent to a Cys group indicate a disulfide bond linking that Cys to an L or H chain, respectively. Other Cys residues are involved in intrachain disulfide loops. The symbol, CHO, represents carbohydrate. Allotype-related substitutions, shown in the table, are discussed in Chapter 9.

Fig. 4.12. Amino acid sequences and sites of enzymatic cleavage in the hinge regions of human and rabbit-y chains. The symbol H represents the site of an interheavy chain disulfide bond and the symbol L designates the site of a heavy-light chain disulfide bond. The halfcystine at position 220 of the rabbit y-chain forms an intrachain disulfide loop with Cys 131 or 132. The Eu numbering system is used (2). Pap, Pep, and T refer to cleavage sites for papain, pepsin, and trypsin, respectively. The site of cleavage of the rabbit H chain by papain is that for molecules of allotype dll. Hydrolysis by papain of molecules of allotype dl2 is described in the text. Cleavage of the rabbit H chain by trypsin at position 220 occurs only after reduction and aminoethylation (by ethyleneimine) of Cys-220. The symbol CHO represents carbohydrate. References are given in the legend of Fig. 4.9.

The most well known and most widely used compounds mentioned in the chapter are the doubly protected monosaccharide derivatives (cf. Schemes 16-18 and 27-29), which serve as building blocks for the regio- and stereospecific synthesis of a host of more complex carbohydrates. A number of newly discovered alkaloids contain fused 5 6 6-triheterocyclic systems these compounds may come from not only traditional (plant) sources, for example, compounds 96, 292-294, 446, and 447, but also insects (compounds 531-533), marine animals of various kinds, for example, sponges (compounds 58 R = H or OH) and ascidians (compound 289), and amphibians (compound 535). Although the majority of these alkaloids are known to be toxic in sufficient quantity, any possible therapeutic applications have apparently not yet been disclosed. 

Fluorescent pseudomonads are capable of synthesizing poly(3HAMCL)s from a large number of substrates. Work on the biotechnological production of poly(3HAMCL) has focused mainly on two model systems - Pseudomonas oleo-vorans and P. putida. P. oleovorans is able to use alkanes and alkenes as substrate due to the presence of the OCT-plasmid while P. putida, which does not have this plasmid, cannot. In contrast to P. oleovorans, however, P. putida can use carbohydrates such as glucose and fructose for the production of poly(3HAMCL). 

The water-soluble vitamins generally function as cofactors for metabolism enzymes such as those involved in the production of energy from carbohydrates and fats. Their members consist of vitamin C and vitamin B complex which include thiamine, riboflavin (vitamin B2), nicotinic acid, pyridoxine, pantothenic acid, folic acid, cobalamin (vitamin B12), inositol, and biotin. A number of recent publications have demonstrated that vitamin carriers can transport various types of water-soluble vitamins, but the carrier-mediated systems seem negligible for the membrane transport of fat-soluble vitamins such as vitamin A, D, E, and K. 

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