4-Thiopyranoside and 4-thiofuranoside derivatives of d-galactosamine
摘要:
Methyl 2-benzamido-2-deoxy-4-thio-alpha-D-galactopyranoside (7) was prepared in different ways starting from methyl 2-benzamido-3,6-di-O-benzoyl-2-deoxy-alpha-D-glucopyranoside (1). A 4,6-epidithiogalactopyranoside was obtained from the 4-O-mesyl derivative of 1. The transformations of 7 into 2-benzamido-2-deoxy-4-thio-D-galactofuran and into the corresponding methyl alpha- and beta-4-thio-D-galactofuranosides are reported. The T-2(3) conformation is proposed for the alpha anomers of the prepared furanoid compounds. (C) 1998 Elsevier Science Ltd.
4-Thiopyranoside and 4-thiofuranoside derivatives of d-galactosamine
摘要:
Methyl 2-benzamido-2-deoxy-4-thio-alpha-D-galactopyranoside (7) was prepared in different ways starting from methyl 2-benzamido-3,6-di-O-benzoyl-2-deoxy-alpha-D-glucopyranoside (1). A 4,6-epidithiogalactopyranoside was obtained from the 4-O-mesyl derivative of 1. The transformations of 7 into 2-benzamido-2-deoxy-4-thio-D-galactofuran and into the corresponding methyl alpha- and beta-4-thio-D-galactofuranosides are reported. The T-2(3) conformation is proposed for the alpha anomers of the prepared furanoid compounds. (C) 1998 Elsevier Science Ltd.
Methyl 2-benzamido-3,6-di-O-benzoyl-2,4-dideoxy-alpha-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-alpha-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-alpha-D-glucopyranoside by double inversion through triflation, inversion at C-4 with NaNO2, triflation of the resulting methyl 2-benzamido-3,6-di-O-benzoyl-2-deoxy-alpha-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-alpha-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. (C) 2003 Elsevier Ltd. All rights reserved.