A Convenient Synthesis of 4-Thio-D-galactofuranose
The synthesis of 4-thio-D-galactofuranose (15) and derivatives, starting from methyl α-D-glucopyranoside (1), is described. Esterification of 1 with N-benzoylimidazole afforded regioselectively methyl 2,3,6-tri-O-benzoyl-α-D-glucopyranoside (2c). Further sulfonylation of HO-4 of 2c gave methyl 2,3,6...
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todo:paper_00223263_v54_n8_p1884_Varela2023-10-03T14:31:18Z A Convenient Synthesis of 4-Thio-D-galactofuranose Varela, O. Cicero, D. De Lederkremer, R.M. The synthesis of 4-thio-D-galactofuranose (15) and derivatives, starting from methyl α-D-glucopyranoside (1), is described. Esterification of 1 with N-benzoylimidazole afforded regioselectively methyl 2,3,6-tri-O-benzoyl-α-D-glucopyranoside (2c). Further sulfonylation of HO-4 of 2c gave methyl 2,3,6-tri-0-benzoyl-4-0-(p-tolyl-sulfonyl)-α-D-glucopyranoside (2e) or methyl 2,3,6-tri-0-benzoyl-4-0-[(p-bromophenyl)sulfonyl]-α-D-glucopyranoside (2f). Nucleophilic substitution of the sulfonyloxy group by thiocyanate led to methyl 2,3,6-tri-0-benzoyl-4-deoxy-4-thiocyano-α-D-galactopyranoside (3). This reaction allowed the simultaneous introduction of a group precursor of thiol and the inversion of the configuration at C-4. Compound 3 was reduced to methyl 4-5-acetyl-2,3,6-tri-0-benzoyl-4-thio-α-D-galactopyranoside (4a) or methyl 2,3,6-tri-0-benzoyl-4-thio-α-D-galacto-pyranoside (4b). The latter was debenzoylated to give methyl 4-thio-α-D-galactopyranoside (5). This product was also obtained by alkaline methanolysis of 3. Ring contraction was achieved by acetolysis of 5, which produced l,2,3,5,6-penta-0-acetyl-4-thio-α-D-galactofuranose (10) and its β-anomer (11) as the main products. The product distribution in the acetolysis reaction of 4-thiopyranose derivatives would depend on the stability of the ionic intermediates involved. O-Deacetylation of 10 led to 4-thio-D-galactofuranose (15). © 1989, American Chemical Society. All rights reserved. Fil:Varela, O. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Cicero, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:De Lederkremer, R.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00223263_v54_n8_p1884_Varela |
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Universidad de Buenos Aires |
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I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| description |
The synthesis of 4-thio-D-galactofuranose (15) and derivatives, starting from methyl α-D-glucopyranoside (1), is described. Esterification of 1 with N-benzoylimidazole afforded regioselectively methyl 2,3,6-tri-O-benzoyl-α-D-glucopyranoside (2c). Further sulfonylation of HO-4 of 2c gave methyl 2,3,6-tri-0-benzoyl-4-0-(p-tolyl-sulfonyl)-α-D-glucopyranoside (2e) or methyl 2,3,6-tri-0-benzoyl-4-0-[(p-bromophenyl)sulfonyl]-α-D-glucopyranoside (2f). Nucleophilic substitution of the sulfonyloxy group by thiocyanate led to methyl 2,3,6-tri-0-benzoyl-4-deoxy-4-thiocyano-α-D-galactopyranoside (3). This reaction allowed the simultaneous introduction of a group precursor of thiol and the inversion of the configuration at C-4. Compound 3 was reduced to methyl 4-5-acetyl-2,3,6-tri-0-benzoyl-4-thio-α-D-galactopyranoside (4a) or methyl 2,3,6-tri-0-benzoyl-4-thio-α-D-galacto-pyranoside (4b). The latter was debenzoylated to give methyl 4-thio-α-D-galactopyranoside (5). This product was also obtained by alkaline methanolysis of 3. Ring contraction was achieved by acetolysis of 5, which produced l,2,3,5,6-penta-0-acetyl-4-thio-α-D-galactofuranose (10) and its β-anomer (11) as the main products. The product distribution in the acetolysis reaction of 4-thiopyranose derivatives would depend on the stability of the ionic intermediates involved. O-Deacetylation of 10 led to 4-thio-D-galactofuranose (15). © 1989, American Chemical Society. All rights reserved. |
| format |
JOUR |
| author |
Varela, O. Cicero, D. De Lederkremer, R.M. |
| spellingShingle |
Varela, O. Cicero, D. De Lederkremer, R.M. A Convenient Synthesis of 4-Thio-D-galactofuranose |
| author_facet |
Varela, O. Cicero, D. De Lederkremer, R.M. |
| author_sort |
Varela, O. |
| title |
A Convenient Synthesis of 4-Thio-D-galactofuranose |
| title_short |
A Convenient Synthesis of 4-Thio-D-galactofuranose |
| title_full |
A Convenient Synthesis of 4-Thio-D-galactofuranose |
| title_fullStr |
A Convenient Synthesis of 4-Thio-D-galactofuranose |
| title_full_unstemmed |
A Convenient Synthesis of 4-Thio-D-galactofuranose |
| title_sort |
convenient synthesis of 4-thio-d-galactofuranose |
| url |
http://hdl.handle.net/20.500.12110/paper_00223263_v54_n8_p1884_Varela |
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