Fucose 2- deoxy derivative

Figure 9.12 Deoxy derivatives. These contain one less oxygen atom than the monosaccharide from which they are derived. 2-Deoxyribose is a most important deoxy pentose and is a major constituent of deoxyribonucleic acid (DNA). Deoxy hexoses are widely distributed among plants, animals and microorganisms especially as components of complex polysaccharides. Examples are rhamnose (6-deoxymannose), a component of bacterial cell walls, and fucose (6-deoxygalactose), which is often found in glycoproteins and is an important constituent of human blood group substances.

Replacement of a hydroxyl group by hydrogen yields a deoxy sugar. The derivative of ribose, deoxyribose, is a component of deoxyribonucleic acid (DNA). Similarly, deoxy derivatives of the two hexoses, galactose and mannose, occur as fucose and rhamnose, respectively, these being components of certain heteropolysaccharides. 

Several deoxy sugars have trivial names established by long usage, e.g. fucose (Fuc), quinovose (Qui) and rhamnose (Rha). They are illustrated here in the pyranose form. These names are retained for the unmodified sugars, but systematic names are usually preferred for the formation of names of derivatives, especially where deoxygenation is at a chiral centre of the parent sugar. (See also the alphabetical listing of trivial names in the Appendix.)... 

The legioselectivity of electrophilic additions of the C=C double bond in 7-oxabicyclo[2.2.1]hept-5-en-2-yl (7-oxanorbom-5-en-2-yl) derivatives depends on the nature of the substituents at C(2). The adducts so-obtained can be transformed into the corresponding 5,6-disubstituted 7-oxanorboman-2-ones, which can be mono-substituted at C(3) stereoselectively, giving products with the same stereochemical information as hexoses. Thus, optically pure 7-oxanorbom-5-en-2-yl derivatives can be viewed as "naked sugars" Applications to the total, asymmetric syntheses of L-daunosamine, 2-deoxy-L-fucose, D- and L-aUose, D- and L-talose, D- and L-ribose,... 

A disaccharide derivative (42) of more conventional structure has also been isolated from hen oviduct.177 Its structure was confirmed by its conversion into L-fucose and uridine 5 -(2-acetamido-2-deoxy-a-D-glucopyranosyl pyrophosphate) after treatment with a-L-fucosi-dase. Mild, acidic hydrolysis of the ester 42 produces a disaccharide whose structure was confirmed by periodate oxidation. Human milk and colostrum,178 or milk and colostrum of pig,128 are also sources of... 

Treatment of the reaction mixture with sodium borohydride-f followed by acidic hydrolysis led to major fractions of 6-deoxy-D-glucose-f and D-fucose-t, together with a minor fraction of D-galac-tose-4-f.422 This fact indicates that 109 is formed as an enzyme-bound intermediate, and allows the exclusion of a possible, alternative mechanism, shown in Fig. 3 as B, for the conversion of 107a into 108a through an intermediate glycos-5-ene derivative 111. 

Finally, the 3-deoxy-D-threo-2-hexulosonate was split291 by an aldolase into pyruvate and 3-deoxy-D-glyceraldehyde, the L-arabino derivative being a rather better substrate than that derived from D-fucose. 

Reduction of dTDP-6-deoxy-D-xy/o-hexos-4-ulose (7a) at C-4 of the hexosyl group should lead to dTDP derivatives of 6-deoxy-D-glucose (d-quinovose) and 6-deoxy-D-galactose (D-fucose). Although D-quinovose and D-fucopyranose have not been found as components of bacterial polysaccharides, the corresponding glycosyl nucleotides were identified147 in extracts of Escherichia coli Y-10. 

A similar mechanism seems probable for conversion of GDP-6-deoxy-D-(yxo-hexos-4-ulose (7c) into GDP-L-fucose (GDP-Fuc),40,159 although, in this case, the enzymes that participated in the process were not separated, and intermediate formation of the 6-deoxy-L-xy/o-hexosyl-4-ulose derivative (8b) was not demonstrated. 

The isolation of D-fucose (6-deoxy-D-galactose) instead of galactose as a major product of the catalytic oxidation-reduction was considered to be the consequence of / -elimination of the initially formed 4-ulose-derivative. The removal of water resulted in the formation of a 4-keto-5,6-glucoseen which upon catalytic reduction yielded 6-deoxy-D-glactose. Thus, it seems that it is the intrinsic property of methyl-D-xylo-4-hexu-loside to undergo molecular rearrangement spontaneously. 

Several deoxy sugars, notably 2-deoxy-D-mY/ o-pentose (2-deoxy-D-ribose) the sugar component of DNA, 6-deoxy-L-mannose (L-rhamnose), 6-deoxy-L-galactose (L-fucose), 6-deoxy-D-glucose (quinovose), and their derivatives, occur very widely in natural products. Also relevant are dideoxy and trideoxy sugars, such as 3,6-dideoxyhexoses, components of the antigenic determinants bacterial... 

Melancon CE IB, Liu HW (2007) Engineered biosynthesis of macrolide derivatives bearing the non-natural deoxysugars 4-epi-D-mycaminose and 3-N-methylamino-3-deoxy-D-fucose. J Am Chem Soc 129 4896 1899... 

Methyl-D-fucose has been prepared by two methods.68 In the first, methyl a-D-galactopyranoside was converted into the 6-tosyl derivative, from which by condensation with acetone methyl 3,4-isopropylidene-6-tosyl-a-D-galactopyranoside (LXIV) was obtained. Methylation gave the corresponding 2-methyl ether which was converted into the 6-deoxy iodide (LXV) by heating with sodium iodide in acetone solution at 140°. Reduction with Raney nickel gave sirupy methyl 2-methyl-3,4-isopro-pylidene-a-D-fucopyranoside (LXVI) from which 2-methyl-D-fucose was obtained on hydrolysis. 

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