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. Can. J. Chem. 57,1244Chem. 57, (1979. Reaction of 3,4,6-tri-0-acetyl-D-galactal with excess ceric ammonium nitrate and sodium azide in acetonitrile produced 2-azido-1-nitrate addition products (53% p-galacto, 22% a-galacto, and 8% a-talo) and N-acetyl-3,4,6-tri-0-acetyl-2-azido-2-deoxy-a-~-galactopyranosylamine was formed, on hydrolysis, in 10% yield. The reaction product provides a convenient source of D-galactosamine and 3,4,6-tri-0-acetyI-2-azido-2-deoxy-a-~-galactopyranosy~ halides. The crystalline j3-chloride is also reported. The use of these glycosyl halides as reactants for the preparation of 2-azido-2-deoxy-a-and -13-D-galactopyranosides under conditions promoted by both mercuric cyanide and silver salts are reported. R. U. LEMIEUX et R. M. RATCLIFFE. Can. J. Chem. 57,1244(1979.La rkaction du tri-0-acktyl-3,4,6 D-galactal avec du nitrate d'ammonium drique en excks et de l'azoture de sodium dans l'adtonitrile conduit aux produits d'addition azido-2 nitrate-1 (53% p-galacto, 22% a-galacto et 8% a-talo); par hydrolyse, il y a formation de la N-acktyltri-0-acktyl-3,4,6 azido-2 dksoxy-2 a-D galactopyrannosylamine avec un rendement de 10%. Le produit de la rkaction s'avkre une source convenable de la D-galactosamine et des halogknures du tri-0-acktyl-3,4,6 azido-2 dksoxy-2 a-D-galactopyrannosyle. On rapporte aussi la formation du chlorure j3 cristallin. On rapporte I'utilisation de ces halogknures de glycosyle cornrne reactifs dans la prkparation des azido-2 dksoxy-2 a-et j3-D-galactopyrannosides dans des conditions favorisks par des sels de cyanure mercurique et d'argent.[Traduit par le journal] Introduction The occurrence of building units derived from 2-acetamido-2-deoxy-a-D-galactopyranose, which are 0-linked to either serine or threonine, in a wide variety of glycoproteins (1, 2) including glycophorin A (3), epiglycanin (4), antifreeze glycoproteins ( 9 , and the human blood specific glycoproteins (6) is well documented. Both a-and P-glycosidic units derived from N-acetyl-D-galactosamine occur in the oligosaccharidic antigenic determinants of a number of glycosphingolipids (7). Thus, there has developed widespread interest in achieving chemical syntheses of oligosaccharides containing these groupings both for immunochemical and enzymological studies (8). However, the lack of a readily accessible supply of either D-galactosamine or of suitable progenitors has curtailed research in this biologically important area. This work was initiated primarily to achieve the syntheses of oligosaccharides related to the A blood determinants (9) but has been extended to the synthesis of the T, T, (lo), and other important human cell-surface antigenic determinants.The major source of D-galactosamine is by way of the acid hydrolysis of chondroitin sulfate (11).

. Can. J. Chem. 58,631 (1980). Nuclear magnetic resonance properties are shown to be in good accord with those that are expected for synthetic oligosaccharides in the conformations which are predicted by hard-sphere molecular modelling and taking into consideration the important contribution by the exa-anomeric effect. The studies involve first a comparison of the PDG~I(IA~)PDGICNAC (Type I) and p~G a l - On montre que les proprietes de rmn sont en accord avec celles attendues pour les oligosaccharides synthetiques selon les conformations prevues par les modeles spheriques rigides et en tenant compte de la contribution importante de l'effet anomkrique eso. Les etudes impliquent en premier lieu une comparaison des structures des disaccharides ~~Gal(1+3)puGlcNAc (type 1) et p~G a l ( 1 4 4 ) P DGIcNAc (type 2) basee principalement sur les donnees de la rmn du I3C et en second lieu I'ttude des relations existant entre les conformations calc~llees et ies parametres de la rmn du lH et du 13C des determinants du groupe sanguin humain qui derivent du noyau disaccharide de type 1. Parmi les structures examinees on trouve le di, tri et tetrasaccharides pour le ABH et les dtterminants antigeniques de Lewis. On note certaines relations immunologiques-conformationnelles.[Traduit par le journal]

. Can. J. Chem. 60, 44 (1982). Hard-sphere (HS) calculations predict three conformers for the branched B human blood group antigenic determinant (arFuc(l+ 2)[c(~Gal(l+ 3 ) I p~G a l ) and two conformers for the linear tetrasaccharide ( a~R h a ( l + 2 ) a~R h a ( l + 3)arRha(l+ 3)-p~G l c N A c ) , which constitutes a part of the repeating unit of the Shigella jexnrri 0-antigen, which differ in conformational energy by less than 0.7 and 0.2 kcal/mol, respectively. However, a detailed 'H nmr study of specific interunit deshielding effects, quantitative treatment of spin-lattice relaxation times. and nuclear Overhauser enhancements requires that only one of the conformers thus predicted be, in fact, conformationally preferred in solution. These conformers are those predicted by hard-sphere e.uoanomeric (HSEA) calculations. [Traduit par le journal] Introduction We have recently published evidence (1) that the addition of the torsion-angle dependent exo-anomeric effect to the ground state energy of an oligosaccharide allowed the conformational preferences about the glycosidic linkages to be assessed by hard-sphere molecular modelling in good agreement with physical evidence based on nmr spectroscopy. The evidence was based mainly on specific interunit deshieldings of protons and interunit nuclear Overhauser enhancements (nOe's) (1, 2). Since then, we have gained more ready access to a