Syntheses of model oligosaccharides of biological significance. 9. Syntheses of trideuteriomethyl di-3,6-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-β-D-galactopyranoside: the I antigen branch-point trisaccharide and related disaccharides

Abstract

. Can. J. Chem. 65,693 (1987). ' The title trisaccharide, 13c, was synthesized, as well as its two component disaccharides, 10c and l l c . Four disaccharides, 3c, 4c, 5c, and 7c, were also prepared to serve as model compounds for the investigation of the 3-dimensional structure of more complex oligosaccharides. The P-1,3 linkage was formed in 75% yield by coupling 3,4,6-tri-0-acetyl-2-deoxy-2-phthalimido-P-D-glucopyranosyl bromide (9) with trideuteriomethyl2-O-benzoyl-4,6-benzylidene-~-~-galactopyranoside (2a), using silver trifluoromethanesulphonate as a promoter in the presence of the base 2,6-di-tert-butyl-4-methylpyridine. Using a silver zeolite as a promoter under a variety of conditions, both a-1,3 and P-1,3 linkages were formed. The P-1,6 linkages were prepared in high yield using 9 and silver zeolite with either trideuteriomethyl 2,3-di-0-benzoyl-P-D-galactopyranoside Chem. 65, 693 (1987). On a synthCtisC le trisaccharide mentionnC dans le titre (13c) ainsi que les deux disaccharides qui le foment (10c et l l c ) . On a aussi prCparC les quatre disaccharides 3c, 4c, 5c et 7c comme composCs modkles pour 1'Ctude de la structure tridimensionnelle d'oligosaccharides plus complexes. On a form6 la liaison P-1,3 avec un rendement de 75% en procCdant au couplage du bromure de tri-0-acttyl-3,4,6 dCoxy-2 phtalimido-2 P-D-glycopyrannosyle (9) avec le 0-benzoyl-2 benzylidkne-4,6 P-D-galactopyrannoside de trideut6romCthyle (2a), sous l'influence du trifluoromCthanesulfonate d'argent comme promoteur de la reaction et en prksence de di-tert-butyl-2,6 mCthyl-4 pyridine comme base. Si on utilise le zeolite d'argent comme promoteur, sous diverses conditions, il y a formation des liaisons a-1,3 ainsi que p-1,3. On a prCparC les liaisons P-1 ,6 avec de bons rendements en faisant rCagir le composC 9, en prCsence de zColite d'argent comme promoteur, avec soit le di-0-benzoyl-2,3 P-D-galactopyrranoside de trideutCromCthyle (86) soit le 0-benzoyl-2 0-(tri-0-acCtyl-3,4,6 dCoxy-2 phtalimido-2 P-D-g1~~0pyrann0~yl)-3 P-D-galactopyrannoside de trideutCromCthyle ( l l b ) . On a utilisC le bromure de tri-0-benzyl-2,3,4 a-L-fucopyrannosyle (lb) pour la fucosylation, catalysCe par les ions halogknures, du composC 2a ou de son isomkre 0-benzoyle-3 (26). Les glycosylations des bromures de di-0-acCtyl-3,6 0-(tCtra-0-acCtyl-2,3,4,6 P-D-gala~topyranno~y1)-4 dCoxy-2 phtalimido-2 P-D-glucopyrannosyle (66) et de 0-(tetra-0-acCtyl-2,3,4,6 P-D-galactopyrannosy1)-4 tri-0-acCtyl-2,3,6 a -D -g l~~~p y r a n n~~y l e (50) par l'heptadeutCro-isopropanol se font sous l'influence du zeolite d'argent comme promoteur.[Traduit par la revue]As part of our program of studies of complex oligosaccharides, in particular those structures related to neoplasia (I), we have synthesized trisaccharide 13c and several related disaccharides 3c, 4c, 5c, 7c, and 10c as their P-glycosides. These anomerically pure oligosaccharides are suitable for the elucidation of their 3-dimensional structures by nrnr spectroscopic techniques (2).1i is our that to understand the biol...

Pyranoside‐into‐Furanoside Rearrangement: New Reaction in Carbohydrate Chemistry and Its Application in Oligosaccharide Synthesis

“…Selective removal of the anomeric acetate in compound 28 followed by treatment with N ‐phenyltrifluoroacetimidoyl chloride afforded galactofuranoside donor 29 . The spacer‐armed glycosyl acceptor 32 was prepared from the known diol 31 37 by regioselective 2‐O‐benzoylation by the method of Szeja38 as modified by Krepinsky 39. Coupling of acceptor 32 and the galactofuranosyl donor 29 proceeded smoothly and gave disaccharide 33 in good yield.…”

Regioselective reductive openings of 4,6-benzylidene acetals: synthetic and mechanistic aspects

“…The acetal can be completely removed by for example mild acidic hydrolysis (usually 80% acetic acid in water), 13 iodine in methanol, 14,15 or by hydrogenolysis (Pd/C in acetic acid or Pd(OH) 2 in ethanol). 16,17 The benzylidene acetals can also be regioselectively opened under oxidative conditions, for example, by N-bromosuccinimide in CCl 4 under basic conditions (usually BaCO 3 ) to give a 4-O-benzoate and bromine in position 6. 18 The addition of water gives the corresponding free 6-OH.…”

Simplifying Oligosaccharide Synthesis: Boronate Diesters as Cleavable Protecting Groups

“…The 1 H and 13 C NMR spectra of 8 closely resembled the reported spectral values for a peracetylated alkyl glycoside of the same disaccharide. 15 This traditional synthesis required 5 chromatographic separations resulting in an overall yield of 42%. The sequence from 7 to pure 8 could be accomplished in 3 days reflecting the simplicity of this approach.…”