Synthesis of 4- C-sulfoaminosugar derivatives: isomerization of 4- C-sulfogalactosamine to its gluco epimer

• Published in: Tetrahedron: asymmetry Vol. 14; no. 23; pp. 3761 - 3768
• Main Authors: Fernández-Bolaños, José G., Garcı́a, Salud, Fernández-Bolaños, José, Diánez, M a Jesús, Estrada, M a Dolores, López-Castro, Amparo, Pérez-Garrido, Simeón
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 28-11-2003
• ISSN: 0957-4166; 1362-511X
• DOI: 10.1016/j.tetasy.2003.10.004

Methyl 2-benzamido-3,6-di-
O-benzoyl-2,4-dideoxy-α-
d-glucopyranoside-4-
C-sulfonate sodium salt
9 and its
galacto epimer
10 were prepared by oxidation with hydrogen peroxide in acetic acid of methyl 4-
S-acetyl-2-benzamido-3,6-di-
O-benzoyl-2-deoxy-4-thio-α-
d-glucopyranoside
7 and its
galacto epimer
8, respectively. The 4-thioglucoside
7 was prepared from methyl 2-benzamido-3,6-di-
O-benzoyl-2-deoxy-α-
d-glucopyranoside by double inversion through triflation, inversion at C-4 with NaNO
2, triflation of the resulting methyl 2-benzamido-3,6-di-
O-benzoyl-2-deoxy-α-
d-galactopyranoside, followed by displacement with potassium thioacetate. Deacylation of
9 with refluxing aqueous sodium hydroxide followed by deionisation yielded methyl 2-amino-2,4-dideoxy-α-
d-glucopyranoside-4-
C-sulfonic acid
11. Deacylation of the galactopyranoside
10 under the same conditions also gave
11, due to base catalysed isomerisation of
galacto to the more stable
gluco configuration. The structure of
11, crystallized as the monohydrate, was confirmed by X-ray crystallographic analysis. The asymmetric unit contains two sugar molecules in two unique but similar conformations and two water molecules. The sulfo and the amino groups form a zwitterion, with each ammonium group hydrogen bonded to the sulfonate groups of two other molecules related by symmetry.
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