Synthesis of the tetrasaccharide alpha-D-Glcp-(1-->3)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->2)-alpha-D-Manp recognized by calreticulin/calnexin.
The title compound as its methyl glycoside was efficiently synthesized using a block synthesis approach. Halide-assisted glycosidations between 6-O-acetyl-2,3,4-tri-O-benzyl-alpha-D-glucopyranosyl iodide and ethyl 2-O-acetyl-4,6-di-O-benzyl-1-thio-alpha-D-mannopyranoside using triphenylphosphine oxide as promoter yielded, with complete alpha-selectivity, a disaccharide building block in high yield. The perbenzylated derivative of this proved to be an excellent donor affording 88% of the protected target tetrasaccharide in an NIS/AgOTf-promoted coupling to a known methyl dimannoside acceptor. Deprotection through catalytic hydrogenolysis then gave the target compound in 47% overall yield.
Gemma
Emiliano
E
Department of Chemistry, Göteborg University, S-412 96 Gothenburg, Sweden.
Lahmann
Martina
M
Oscarson
Stefan
S
D037281:Calnexin / Q000737:chemistry* / Q000378:metabolism; D037282:Calreticulin / Q000737:chemistry* / Q000378:metabolism; D002240:Carbohydrate Sequence; D002384:Catalysis; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry* / Q000378:metabolism; D013865:Thioglycosides / Q000138:chemical synthesis / Q000737:chemistry
D037282:Calreticulin; D009844:Oligosaccharides; D013865:Thioglycosides; D037281:Calnexin