Concise synthesis of a hexasaccharide present in the cell wall lipopolysaccharide of Azospirillum lipoferum Sp59b

Concise chemical synthesis of a hexasaccharide repeating unit found in the cell wall lipopolysaccharide of Azospirillum lipoferum Sp59b was achieved in excellent yield. A [3+3] block synthetic strategy has been applied for the construction of the target hexasaccharide. During the synthesis, the orthogonal property of thioglycosides has been successfully exploited. Yields were high in all intermediate steps.

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4-Methoxyphenyl (2,3-di-O-benzyl-4,6-O-benzylidene-α-d-galactopyranosyl)-(1→3)-2,4,6-tri-O-benzyl-β-d-galactopyranosideC55H62O18[α]D25=+5.4 (c 1.0, CHCl3)Source of chirality: d-galactose

4-Methoxyphenyl (2,3,6-tri-O-benzyl-α-d-galactopyranosyl)-(1→3)-2,4,6-tri-O-benzyl-β-d-galactopyranosideC55H64O18[α]D25=+3.6 (c 1.0, CHCl3)Source of chirality: d-galactose

4-Methoxyphenyl (2,3-di-O-acetyl-4,6-O-benzylidene-β-d-glucopyranosyl)-(1→4)-(2,3,6-tri-O-benzyl-α-d-galactopyranosyl)-(1→3)-2,4,6-tri-O-benzyl-β-d-galactopyranosideC72H82O25[α]D25=+2.2 (c 1.0, CHCl3)Source of chirality: d-glucose, d-galactose

Ethyl 2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl-(1→3)-2-O-acetyl-4-O-benzyl-1-thio-α-l-rhamnopyranosideC29H40O12S[α]D25=-8.8 (c 1.0, CHCl3)Source of chirality: l-rhamnose

4-Methoxyphenyl (2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl)-(1→3)-(2-O-acetyl-4-O-benzyl-α-l-rhamnopyranosyl)-(1→2)-3,4-di-O-benzyl-α-l-rhamnopyranosideC54H64O18[α]d25=-6 (c 1.0, CHCl3)Source of chirality: l-rhamnose

4-Methoxyphenyl (2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl)-(1→3)-(2-O-acetyl-4-O-benzyl-α-l-rhamnopyranosyl)-(1→2)-(3,4-di-O-benzyl-α-l-rhamnopyranosyl)-(1→3)-(4,6-O-benzylidene-β-d-glucopyranosyl)-(1→4)-(2,3,6-tri-O-benzyl-α-d-galactopyranosyl)-(1→3)-2,4,6-tri-O-benzyl-β-d-galactopyranosideC131H142O31[α]D25=-10 (c 1.0, CHCl3)Source of chirality: l-rhamnose, d-glucose, d-galactose

4-Methoxyphenyl (2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl)-(1→3)-(2-O-acetyl-4-O-benzyl-α-l-rhamnopyranosyl)-(1→2)-(3,4-di-O-benzyl-α-l-rhamnopyranosyl)-(1→3)-(2-O-acetyl-4,6-O-benzylidene-β-d-mannopyranosyl)-(1→4)-(2,3,6-tri-O-benzyl-α-d-galactopyranosyl)-(1→3)-2,4,6-tri-O-benzyl-β-d-galactopyranosideC133H144O32[α]D25=-7.1 (c 1.0, CHCl3)Source of chirality: l-rhamnose, d-glucose, d-galactose

4-Methoxyphenyl (α-l-rhamnopyranosyl)-(1→3)-(α-l-rhamnopyranosyl)-(1→2)-(α-l-rhamnopyranosyl)-(1→3)-(β-d-mannopyranosyl)-(1→4)-(α-d-galactopyranosyl)-(1→3)-β-d-galactopyranosideC43H68O29[α]D25=+2.7 (c 1.0, CH3OH)Source of chirality: l-rhamnose, d-glucose, d-galactose