Galactose derivatives

R = 1-BuMe2Si, = a, then D-glucose derivative,b)— = p,then D-galactose derivative... 

L2. Leloir, L. F., The enzymatic transformation of uridine diphosphate glucose into a galactose derivative. Arch. Biochem. Biophys. 33, 186-190 (1951). 

Unprotected galactose derivatives may be readily transformed into the trichloroacetimidates 8a-8g, as shown in Table VIII. Again, as demonstrated for the O-benzyl-protected compounds 8a, either the a-trichloroace-timidate 8a-a or the / -trichloroacetimidate 8a -/ may be obtained highly selectively, depending on the base used for the catalysis of the addition to the trichloroacetonitrile. 

A similar picture has been obtained very recently for novel multi-step bio-chemo cascade reactions starting from both galactose-derived polyols and aliphatic mono- and diols [29]. Galactose oxidase and alcohol oxidase show complementary synthetic use for this range of alcohols (Table 13.3) [30], allowing in situ... 

In an alternative approach the site-selective functionalization reaction has been used to incorporate a galactose derivative into a folded foux-hehx bundle protein and the effect of glycosylation on the structure of the folded protein has been identified [65]. The unfunctionalized designed four-helix bundle did not have a well-defined tertiary structure but the introduction of the sugar improved the helical content and reduced the rate of conformational exchange. Glycosylation may therefore play a role in the maturation of poorly folded proteins. 

Fig. 4. 2-Amino-2-deoxyglycoseptanosides prepared using D-glucose- and D-galactose-derived septan-sosyl donors 72 and 74, (Shown in Scheme 14) respectively.

R. Batchelor, J. E. Harvey, P. T. Northcote, P. Teesdale-Spittle, and J. O. Hoberg, Heptanosides from galactose-derived oxepenes via stereoselective addition reactions, J. Org. Chem., 74 (2009) 7627-7632. 

Alkyl (or acyl) derivatives of the 6-amino-6-deoxy carbohydrates are examples of derivatives in which the hydrophilic and hydrophobic moieties are linked at other positions than C-1. Thus 6-amino-6-deoxy-D-galactose derivatives 34 were prepared from l,2 3,4-di-0-isopropylidene-6-0-tosyl-a-D-galacto-pyranose by the following reactions (1) substitution of the leaving group at C-6 by a phthaloyl function, (2) hydrazinolysis to afford a 6-amino-6-deoxy intermediate, (3) reaction of acyl or sulfonyl chlorides at the amino function, (4) deprotection of the acetal rings to afford the expected glycolipid 34 [56]. 

Nitrile imines are related to azomethine imines, in the same manner as nitrile oxides are related to nitrones. In a single and recent report, the reactions of D-galactose derived chiral nitrile imines have been described (104). However, in reactions with nonchiral alkenes, no diastereoselection was obtained. 

Karlsson and Hogberg (291,292) applied the thiocarbonyl ylide 175 in a diastereoselective 1,3-dipolar cycloaddition with 165. The thiocarbonyl yhde was generated in situ by an elimination reaction. The reaction with 165 gave 176 (R = Bu, BnO, Ph) with selectivities of up to 64—80% de. Furthermore, the cycloaddition of a chiral galactose-derived nitrile imine with 165 has been reported (104). 

Thymidine 5 -(a-D-glucopyranosyl pyrophosphate) (4) and the analogous D-galactose derivative have been isolated from extracts of Pasteurella pseudo tuberculosis.102 The ester of thymidine 5 -pyro-phosphate with a-D-mannopyranose was found in an extract of Strep-tomyces griseus,14,103 and the occurrence of the D-ribosyl ester in the... 

An example of a sugar-derived chiral -haloketone is offered by 24. When ulosyl bromide 24 is coupled to acetaldehyde in a Grignard-type process, a mixture of isomeric adducts is formed, where the 50% is represented by 25, possessing the (R) configuration at the hydroxy ethyl substituent (equation 21). The same protocol is applied in an efficient nucleophilic C-glycosidation reaction of 24 with galactose-derived aldehyde 26 to give 27 (equation 22)20. 

The methylated D-galactose derivatives 66 and 67 were thereafter released by mild hydrolysis with acid. The product was reduced with sodium borodeuteride, the reduction product methylated with trideuteriomethyl iodide, and the ether analyzed. From the disappearance of the ethers derived from the uronic acid and the 2-substi-tuted L-rhamnose, and the appearance of the ethers 68 and 69, the... 

In addition, by using various D-galactose derivatives, deductions could be made with regard to the contributions of portions of the Gal2 molecule to its total binding-energy with these two im-... 

A. Lubineau and R. Lemoine, Regjoselective sulfation of galactose derivatives through the sttumylene procedure. New synthesis of the 3 -(>-sulfated Lewis trisaccharide. Tetrahedron Lett 35 8795 (1994). 

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