Four-component one-pot synthesis of a branched manno-pentasaccharide: tert-butyldiphenylsilyl ether as an in situ removable carbohydrate-protecting group

Use of iodine for efficient and chemoselective glycosylation with glycosyl ortho-alkynylbenzoates as donor in presence of thioglycosides

“…The reason may be attributed to the increased reactivity of 3-OH induced by free 2-OH. 17,21 (see Scheme 3) In conclusion, we have developed a simple and highly efficient glycosylation protocol for glycosyl ortho-alkynylbenzoates, which are easily prepared and stable under standard laboratory conditions. Glycosylation occurs at room temperature utilizing iodine as the mild promoter, which is cheap, easily available, non-toxic and convenient to use.…”

One‐Pot Methods for the Protection and Assembly of Sugars

“…Remarkably, the application of donors having the thiobenzoxazolyl, thioethyl, and thiothiazolyl leaving groups allowed three glycosidic bond formations in a one‐pot sequence 44. The notable structures assembled using this technique included diosgenyl saponins,45 a mucin core branched pentasaccharide,46 a glycosylated amino acid,47 sialosides,43a,48 a flaccidoside II trisaccharide fragment,49 glycosaminoglycans,50 oligomannosides,51 and the Forssman antigen pentasaccharide and derivatives 52…”

“…Similar approaches were implemented in one pot using protecting groups that could be removed or manipulated in situ . Because glycosylations typically occur in an acidic environment, acid‐labile protecting groups, such as PMB,88 TBS,32,89 and TBDPS51 groups, were successfully utilized. For the procedure to work, glycosylations were performed at subzero temperatures and the deprotection stage required raising the reaction temperature and addition of more acid catalyst (TfOH, TMSOTf, or BF 3 ⋅Et 2 O).…”

Convergent Synthesis of the Pentasaccharide Repeating Unit of the O-Antigen of Escherichia coli O36

“…To synthesize trisaccharide 15, a number of suitable functionalized monosaccharide intermediates 9, 10, 21 and 11 22 were prepared from the reducing sugars following reported reaction conditions in the literature (Scheme 1). Transformation of L-fucose tetraacetate (6) into 4-methoxyphenyl 2,3,4-tri-O-acetyl-β-L-fucopyranoside (7) was carried out in 77% yield by treatment with 4-methoxyphenol and boron trifluoride-diethyl ether at 0 °C.…”