Conformationally restricted 3,5-O-(di-tert-butylsilylene)-D-galactofuranosyl thioglycoside donor for 1,2-cis a-D-galactofuranosylation
A conformationally restricted 2-O-benzyl-3,5-O-di-tert-butylsilylene-b-D-thiogalactofuranoside donor was prepared from benzyl alpha-D-galactofuranoside and its donor capability was studied for stereoselective 1,2-cis a-D-galactofuranosylation. An unusual chemical behavior on benzylation and hydrogen...
| Autores: | , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2014 |
| País: | Argentina |
| Institución: | Consejo Nacional de Investigaciones Científicas y Técnicas |
| Repositorio: | CONICET Digital (CONICET) |
| Idioma: | inglés |
| OAI Identifier: | oai:ri.conicet.gov.ar:11336/8158 |
| Acceso en línea: | http://hdl.handle.net/11336/8158 |
| Access Level: | acceso abierto |
| Palabra clave: | Glycosylation Thioglycoside 1,2-Cis Galactofuranose Solvent Effects Protecting Groups https://purl.org/becyt/ford/1.4 https://purl.org/becyt/ford/1 |
| Sumario: | A conformationally restricted 2-O-benzyl-3,5-O-di-tert-butylsilylene-b-D-thiogalactofuranoside donor was prepared from benzyl alpha-D-galactofuranoside and its donor capability was studied for stereoselective 1,2-cis a-D-galactofuranosylation. An unusual chemical behavior on benzylation and hydrogenolysis reactions was observed after the introduction of the 3,5-O-di-tert-butylsilylene protecting group into the galactofuranosyl moiety. The influence of the solvent, temperature and activating system was evaluated. The NIS/AgOTf system, widely used in 1,2-cis b-arabinofuranosylation, was not satisfactory enough for 1,2-cis galactofuranosylation. However, moderate to high alpha-selectivity was obtained with all the acceptors employed when used p-NO2PhSCl/AgOTf as a promoting system, in CH2Cl2 at -78 ºC. The order of the addition of the reactants (premixing or preactivation) did not affect substantially the stereochemical course of the glycosylation reaction. The a-D-Galf-(1-6)-D-Man linkage was achieved with complete diastereoselectivity by preactivation of the conformationally constrained thioglycoside donor. |
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