Coupling reactions of O-(trimethylsilyl) glycosides and 6-O-(tert-butyldiphenylsilyl)-protected galactosides in the presence of trimethylsilyl triflate. A new method of forming .beta.-(1 .fwdarw. 6)-oligosaccharidic linkages

Isolation, Synthesis, and Antiplatelet Aggregation Activity of Resveratrol 3-O-β-d-Glucopyranoside and Related Compounds

“…This approach, however, proved less convenient since the protective acetyl group was partially removed during both the Wittig and the glucosylation reactions and the chemical yield of the Wittig reaction was lower (72%). In addition, direct treatment of the Wittig adduct ( E )-3,5-bis[( tert -butyldimethylsilyl)oxy]-4‘-acetoxystilbene with 1- O -(trimethylsilyl)-2,3,4,6-tetra- O -acetylglucose , which a priori appeared to be the most straightforward glucosidation procedure, led to recovery of starting material (48%), accompanied by a mixture of the tetra- O -acetyl-3-β- O -glucopyranosides of ( E )-3,5-dihydroxy-4‘-acetoxystilbene, ( E )-4‘-acetoxy-5-[( tert -butyldimethylsilyl)oxy]-3-hydroxystilbene, and ( E )-3,4‘-dihydroxy-5-[( tert -butyldimethylsilyl)oxy]stilbene. Acetylation of the mixture gave the tetra- O -acetyl-3- O -β- d -glucopyranoside of 4‘,5-diacetoxy-3-hydroxystilbene, identical in all respect to an authentic sample.…”

Catalytic Decarboxylative Glycosylation Promoted by Hafnium(IV) ­Trifluoromethanesulfonate: β-Selective Glycosylation via a Mixed Carbonate of an Acyl-Protected Donor Sugar

“…In conclusion, we have reported b-selective glycosylation reactions that are efficiently catalyzed by Hf(OTf) 4 . We believe that this method provides great advantages for the solid phase synthesis of oligosaccharides, and we are currently exploring such applications.…”

“…In the prevailing methods, the catalytic glycosylation will be usually disturbed by deactivation of a promoter due to interaction with the conjugate acid of the leaving group or inefficiency in the nucleophilicity of the alcohol oxygen of an accepter. In the past few decades, it has been successful to use (CH 3 ) 3 Si, 3 t-Bu(CH 3 ) 2 Si, 4 or a trityl group 5 as a cap of the acceptor alcohol. In all cases, the use of a drying agent or more than 10 mol% of a promoter was required for completion of the catalytic reaction.…”

Catalytic Glycosylations in Oligosaccharide Synthesis

“…0.5 equiv) (Scheme ). Acetylated galactosyl- and glucosyl donors were coupled to the 6-O of a sugar acceptor with galacto stereochemistry (up to a trisaccharide). Acetyl, benzoyl, and p -phenylbenzoyl groups were tolerated under the relatively mild conditions (i.e., CH 2 Cl 2 or C 2 H 4 Cl 2 at low temperature, from −78 to −30 °C), giving good yields in the range of 47 to 76%.…”