Synthesis of alpha-lactosyl-(1-->3)-L-glycero-alpha-D-manno-heptopyranoside, a partial oligosaccharide structure expressed within the lipooligosaccharide produced by Neisseria gonorrhoeae strain 15253.
The glycosyl donor, hepta-O-benzyl-beta-lactosyl trichloroacetimidate (4) was prepared by treating hepta-O-benzyl-lactose with trichloroacetonitrile in the presence of potassium carbonate. The acceptor, methyl 2-O-benzyl-4,6-O-benzylidene-7,8-dideoxy-alpha-D-manno-oct-7-enopyranoside (8) was synthesized by hydrolysis of a 3,4-butane diacetal of methyl L-glycero-alpha-D-manno-oct-enopyranoside and subsequent benzylidenation. Glycosidation of the donor 4 with the acceptor 8 in 1,4-dioxane using Me(3)SiOTf as a promoter for 1 h at room temperature gave methyl (2,3,4,6-tetra-O-benzyl-beta-D-galactopyranosyl)-(1-->4)-(2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl)-(1-->3)-2-O-benzyl-4,6-O-benzylidene-7,8-dideoxy-alpha-D-manno-oct-7-enopyranoside (9) as a major product (59%). The oct-enopyranoside moiety of the trisaccharide 9 was converted to a heptopyranoside (80%) by oxidative cleavage with OsO(4)-NaIO(4) and subsequent reduction. Hydrogenolysis of the resulting trisaccharide and subsequent acetylation gave the peracetate of alpha-lactosyl-(1-->3)-Hep. Deacetylation of the peracetate afforded the title trisaccharide.
Ishii
Kazuyuku
K
Department of Biochemistry and Biotechnology, Tottori University, Koyama-Minami 4-101, Tottori 680-8553, Japan.
Kubo
Hiroyuki
H
Yamasaki
Ryohei
R
D000939:Epitopes / Q000737:chemistry; D006027:Glycosides / Q000138:chemical synthesis* / Q000737:chemistry; D008070:Lipopolysaccharides / Q000096:biosynthesis / Q000737:chemistry*; D009344:Neisseria gonorrhoeae / Q000737:chemistry* / Q000378:metabolism; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D014312:Trisaccharides / Q000138:chemical synthesis* / Q000737:chemistry
D000939:Epitopes; D006027:Glycosides; D008070:Lipopolysaccharides; D009844:Oligosaccharides; D014312:Trisaccharides; C008245:lactosides; C023023:lipid-linked oligosaccharides