| Popis: |
We prepared several kinds of 1- C -alkyl-2,3,4,6-tetra- O -benzyl-α- d -glucopyranose derivatives containing methyl, ethyl, n -butyl, and benzyl groups as the alkyl groups at their anomeric positions. The Lewis acid- or Bronsted acid-catalyzed O-glycosidations using them as the glycosyl donors to synthesize 1- C -alkyl- d -glucopyranosides were investigated. Using 10 mol % of triphenylmethyl perchlorate efficiently catalyzed the glycosidation of 2,3,4,6-tetra- O -benzyl-1- C -methyl-α- d -glucopyranosyl dimethylphosphinothioate. The glycosidation using the 1- C -alkyl-2,3,4,6-tetra- O -benzyl-α- d -glucopyranosyl acetates smoothly proceeded in the presence of only 5 mol % of scandium(III) trifluoromethanesulfonate. The dehydration–condensation type glycosidation using the 1- C -alkyl-2,3,4,6-tetra- O -benzyl-α- d -glucopyranoses was significantly promoted using 5 mol % of bis(trifluoromethane)sulfonimide. These glycosidations successfully afforded various 1- C -alkyl-α- d -glucopyranosides in good yields with high α-stereoselectivities. |
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