Carbohydrates amino

The [3+2] cycloaddition strategy provides an effective method to access valuable intermediates for the construction of biologically important alkaloids, amino acids, amino carbohydrates and P-lactams [58-62]. The reaction involves the concerted pericyclic addition of a dipole and a dipolarophile and considerable efforts have been made to render these reactions asymmetric nsing Lewis acid catalysis and chiral anxiliaries [63]. 

Kunz and Pfrengle [96] introduced the formation of a-amino-acid derivatives by U-4CR with chiral O-acylated amino-carbohydrates like 2i and formic acid 3f. Usually, their products are formed relatively stereoselectively, and generally in good yield. It seems that the use of formic acid 3f proceeds in the U-4CRs better than do other acid components of 3A, as its amine components like 2i are sterically hindered. The essential disadvantage of the products 18p is that subsequent cleavage of its C-N bond into 33 and 34 can be accomplished only by strong acids such as HC1. Thus, it is doubtful if delicate chiral a-amino acid derivatives or peptides can be prepared successfully in this manner. 

Later, several other types of 1-amino-carbohydrate derivatives like 2j and 2k were used, in order to obtain products of peptide derivatives 18A by the U-4CR. These could be cleaved more efficiently, but not yet well enough [97]. 

Recently, some other amino carbohydrates (e.g. 21) were introduced whose endocyclic oxygen was replaced by nitrogen derivatives like 36 - 21. It appears that all such a-amine components of peptide syntheses by U-4CRs have desirable properties [75]. 

Some mononuclear Cu(II) complexes have been also reported to act as catalysts in the catechol oxidation 146,151,165). The efficiency of these systems is very low and in general it is always possible that the actual species responsible for catechol oxidation is a dimeric species resulting from aggregation of two mononuclear units, as it has been recently shown for an amino-carbohydrate-copper(II) system 156). 

A survey of the utility of 1-thiazoles as masked aldehyde equivalents in amino-carbohydrate synthesis has appeared and describes routes to a range of 2-amino-sugars, azasugars and higher amino-sugars (including desmotic acid and lincosamine). ... 

We mentioned in Section 7 6 that the d l system of stereochemical notation while outdated for most purposes is still widely used for carbohydrates and amino acids Likewise Fischer projections find their major application m these same two families of compounds... 

Polyethylene (Section 6 21) A polymer of ethylene Polymer (Section 6 21) Large molecule formed by the repeti tive combination of many smaller molecules (monomers) Polymerase chain reaction (Section 28 16) A laboratory method for making multiple copies of DNA Polymerization (Section 6 21) Process by which a polymer is prepared The principal processes include free radical cationic coordination and condensation polymerization Polypeptide (Section 27 1) A polymer made up of many (more than eight to ten) amino acid residues Polypropylene (Section 6 21) A polymer of propene Polysaccharide (Sections 25 1 and 25 15) A carbohydrate that yields many monosacchande units on hydrolysis Potential energy (Section 2 18) The energy a system has ex elusive of Its kinetic energy... 

Biosynthetic Human Insulin from E. coli. Insulin [9004-10-8] a polypeptide hormone, stimulates anaboHc reactions for carbohydrates, proteins, and fats thereby producing a lowered blood glucose level. Porcine insulin [12584-58-6] and bovine insulin [11070-73-8] were used to treat diabetes prior to the availabiHty of human insulin [11061 -68-0]. AH three insulins are similar in amino acid sequence. EH LiHy s human insulin was approved for testing in humans in 1980 by the U.S. EDA and was placed on the market by 1982 (11,12). 

Early investigators grouped alkaloids according to the plant families in which they are found, the stmctural types based on their carbon framework, or their principal heterocycHc nuclei. However, as it became clear that the alkaloids, as secondary metaboUtes (30—32), were derived from compounds of primary metabohsm (eg, amino acids or carbohydrates), biogenetic hypotheses evolved to link the more elaborate skeletons of alkaloids with their simpler proposed pregenitors (33). These hypotheses continue to serve as valuable organizational tools (7,34,35). 

Fig. 3. Fluman LH, FSH, and TSH a suburnt [69431-84-1]. Amino acid numbering is relative to maximum homology between species (48). Note the 4 amino acid deletion in human a suburnt between positions 6 and 9. Consensus glycosylation sites are at Asn-56 and 82. GHO = carbohydrate chain.

Fig. 3. Human CG, hLH, and equine CG (eCG) P-subunits. Amino acid numbeiing is relative to maximum homology between the three subunits. Consensus glycosylation sites ate at Asn-13 and 30. = same amino acid as hCG/3. Underlined Asn residues indicate attachment of N-linked carbohydrate chains. Serines at positions 121, 127, 132, and 138 of hCGP are underlined to indicate sites of O-linked carbohydrate attachment. Residues 115—118,...

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