Blood group H type

The intermediate trisaccharide (270) on deprotection gave the blood-group H (type 1) trisaccharide (278), and (271) was also condensed with tetra-O-benzyl-galactopyranosyl bromide in the presence of silver carbonate — silver perchlorate or mercury (II) cyanide to give a tetrasaccharide derivative which was converted into the blood-group B (type 1) tetrasaccharide (279). The blood-group A (type 2) tetrasaccharide (280) was prepared from the a-anomer of the bromide (275) by Paulsen and co-workers [156] via an intermediate trisaccharide used for the preparation of the blood-group B (type 2) tetrasaccharide (see Sect. 6.1). 

Nashed and Anderson [155] prepared an isomer of the blood-group B (type 2) tetrasaccharide with lactosamine substituted at the 4 -position with an a-D-galactosyl residue and at the 2 -position with an a-L-fucosyl residue. For this purpose, the lactosamine derivative (331), prepared via (330), was a-glycosylated with tetrabenzyl-galactosyl bromide in the presence of silver carbonate and silver triflate and the benzoyl group removed from the product so that the 2 -position could be fucosylated with the bromide (302) in the presence of bromide ion. If the fucose residue was added first to the lactosamine derivative (332), then the product (333) [which was converted into the trisaccharide of the blood group H (type 2)] would not react with the tetrabenzyl-galactosyl bromide. 

The blood-group H (type 2) trisaccharide L-fuc-a-(l —>2)-gal-P-(l —>4)-7VAcglc was also prepared by Matta and co-workers [230] by glycosidation of the lactosamine derivative (340) with the fucosyl bromide (322) in the presence of bromide ion and subsequent deprotection. 

P. A. Prieto, R. D. Larsen, M. Cho, H. N. Rivera, A. Shilatifard, J. B. Lowe, R. D. Cummings, D. F. Smith, Expression of human H-type alpha 1,2-fucosyltransferase encoding for blood group H(0) antigen in Chinese hamster ovary cells. Evidence for preferential fucosylation and truncation of polylactosamine sequences, J Biol Chem, (1997), 272, 2089-97. 

The ABO substances have been isolated and their structures determined simphfied versions, showing only their nonreducing ends, are presented in Figure 52—6. It is important to first appreciate the structure of the H substance, since it is the precursor of both the A and B substances and is the blood group substance found in persons of type O. H substance itself is formed by the action of a fiicosyltransferase, which catalyzes the addition of the terminal fiicose in al —> 2 linkage onto the terminal Gal residue of its precursor ... 

Figure 52-6. Diagrammatic representation of the structures of the H, A,and B blood group substances. R represents a long complex oligosaccharide chain, joined either to ceramide where the substances are glycosphingolipids, or to the polypeptide backbone of a protein via a serine or threonine residue where the substances are glycoproteins. Note that the blood group substances are biantenna ry ie, they have two arms, formed at a branch point (not indicated) between the GIcNAc—R, and only one arm of the branch is shown. Thus, the H, A,and B substances each contain two of their respective short oligosaccharide chains shown above. The AB substance contains one type A chain and one type B chain.

Scheme 2.9 Solid-phase synthesis of an H-type 2 blood group determinant.

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