Synthesis from Amino-sugars

2 Synthesis from Amino-sugars. - The 2,4-diamino-2,4,6-trideoxy-D-guloside 

The L-sugar analogue 118 was prepared by C-5 inversion (sulfonate displacement) in an open chain intermediate en route to 117 (X=N3). A precursor for purpurosamine synthesis, 6-acetamido-3,4,6-trideoxy-D-glucal, was obtained in 63% e.e. by lipase-catalysed enantioselective JV-acetylation of the corresponding racemic acrolein-derived amine. Syntheses of various 4-deoxy-4-guanadino-analogues of. -acetylneuraminic acid and its 2-deoxy-2,3-unsaturated derivative, are covered in Chapter 16. 

Chilton, A.M. Stomp, V. Beringue, H. Bouzar, V. Vaudequin-Dransart, A. Pettit and Y. Dessaux, Phytochemistry, 1995,40, 619. 

Vega-Perez, J.I. Candela, M. Vega and F. Iglesias-Guerra, Carbohydr. Res., 1995,279, C5. 

Sharma and S. Singh, Indian J. Chem., Sect. B Org. Chem. Inch Med. Chem., 1994,33B, 851 Chem. Abstr., 1995,122,106 310) 

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Figure 20.2 A summaiy of the pathways for synthesis of the major macromolecules or macrostructures that are required to complete a cell cycle. These processes, except for formation of amino sugars and ATP generation, are described and discussed in this chapter. The synthesis of amino sugars is described in Appendix 6.2. The pathways for the generations of ATP from both glucose and glutamine are described in Chapters 6, 9 and 11. The role of the glycocalyx in the cell is discussed in Chapters 4 and 5.

Stereoselective elongation of the carbon skeleton is the central point of the synthesis of amino sugars from a-amino acids and their derivatives (Scheme 1). 

Literature data on the carbon skeleton elongation may be classified according to the number of carbon atoms added. Such a classification, although far from being ideal, is useful from the synthetic viewpoint. Scheme 2 illustrates the usefulness of a-amino acids (in particular a-amino-(3-hydroxy acids e.g., serine, threonine, and their homologues) in the synthesis of amino sugars. 

P. M. Collins and W. G. Overend, The synthesis of amino-sugars from glycopyranosi-duloses, J. Chem. Soc., (1965) 3448-3456. 

Some reference should be made in this review to Fischer and Leuchs synthesis of glucosamine from o-arabinose through the essential steps of the Fischer higher-carbon sugar process. However, the subject of the synthesis of amino sugars, which was later developed so extensively by P. A. Levene, has been reviewed in his monograph. 

De novo synthesis of amino sugars starts from glucose-6-phosphate, but salvage pathways can also operate. Some reactions involved are shown in Figure 15-18. Incorporation of amino sugars into biological macromolecules is described in Chapter 16. 

Ureas prepared from primary allylic amines slowly decomposed under the conditions listed without providing any cyclized products. Furthermore, the synthesis of amino sugars by the IBX-mediated cyclization protocol was also accomplished. This method was found to be stereoselective. A few examples are listed below ... 

R. Kuhn, G. Kruger, J. Haas, and A. Seeliger, Amino sugar synthesis. XXXIV. Pyrazine formation from amino sugars, Justus Liebigs Ann.Chem., 644 (1961) 122-127. 

In several syntheses, nitrogen is derived directly from the amide group of L-glutamine, e.g. in histidine synthesis conversion of chorismate into anthranilate (see Tryptophan synthesis) synthesis of amino sugars amination of UTP to CTP. 

By its very nature, the process of chemical bond formation between hyaluronan maao-molecules and organic compounds under the joint action of pressure and plastic deformation is similar to the reaction of polypeptide synthesis from amino acids or polysaccharides formed from simple sugar. The formation of chemical bonds can be visualized as a joining of -OH, -COOH and -NH groups accompanied by removal of the water molecule. However, in aqueous mediums, equilibrium of this type of reaction is shifted towards parent substances rather than the products of the reaction. Therefore, such reactions, both in living systems and under laboratory conditions, are achieved as a result of a complex multistage process, far from being similar to a simple process of water removal. The proposed solid-phase... 

The synthesis of amino-sugars from smaller chiral starting materials has again featured in several reports. 3-Benzamido-2,3-... 

A number of synthesis of amino-sugars from chiral non-carbohydrate starting materials have been reported. A reaction sequence used previously to synthesize 2-amino-2-deoxy-D-ribose from 2,3-0-isopropylidene-D-glyceraldehyde (V0I.I6, p.92-3) has been improved K) achieve better stereoselectivity in the initial aldol condensation used to extend the chain by two carbon atoms. The synthesis of a 6,6,6-trifluoro-L-daunosamine derivative from 2,3-0-cyclohexylidene-D-glyceraldehyde is covered in Chapter 8, and of 2,5-dideoxy-2,5-imino-pentonic acids from tartaric acid in Chapter 16. 

Synthesis of amino-sugar glycosides is covered in Chapter 3, the formation of 2-acetamido-2-deoxy-D-glucosides from diazirines via glycosyl carbenes in Chapter 10, and the conversion of a deoxynojirimycin derivative into 2,6-dideoxy-2,6-imino-L-gulonic acid in Chapter 18. 

Scheme 15 Nicolaou s IBX-mediated synthesis of amino-sugar templates from allylic alcohols and aryl isocyanate.

As shown in Figure 45.1, the bases appear in complementary pairs, A with T and G with C in this particular example, the sequence for one strand of DNA is A-T-C-G-T- while the other strand is -T-A-G-C-A-. The sequences of the bases attached to the sugar-phosphate backbone direct the production of proteins from amino acids. Along each strand, groups of three bases, called codons, correspond to individual amino acids. For example, in Figure 45.1, the triplet CGT, acting as a codon, would correspond to the amino acid serine. One codon, TAG, indicates where synthesis should begin in the DNA strand, and other codons, such as ATT, indicate where synthesis should stop. 

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