title: Glycosylation studies on conformationally restricted 3,5-O-(di-tert-butylsilylene)-D-galactofuranosyl trichloroacetimidate donors for 1,2-cis α-D-galactofuranosylation.
abstract: Conformationally restricted 3,5-O-di-tert-butylsilylene-D-galactofuranosyl trichloroacetimidate donors were synthesized from allyl α-D-galactofuranoside for the construction of 1,2-cis α-D-galactofuranosyl linkages. Glycosylation reactions were performed with several acceptors, including D-galactono-1,4-lactone, D-rhamnopyranosyl, and D-mannopyranosyl derivatives. The influence of the temperature and the reaction solvents was evaluated, as well as the 6-O-substitution pattern of the donor. The higher α-selectivities were obtained at -78 °C in diethyl ether as solvent. 6-O-Acetyl substitution on constrained donor increased the α-selectivity compared to the 6-O-benzyl substitution. Almost no selectivities were observed in the non-participating solvent CH(2)Cl(2). In contrast, ethereal solvents enhanced the α-selectivity suggesting a participating effect in the reaction intermediate.
authors: CIHIDECAR, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina.
authors: Mariano J
authors: MJ
authors: Tilve
authors: Carola
authors: C
authors: Gallo-Rodriguez
mesh_terms: D002236:Carbohydrate Conformation; D005663:Furans / Q000737:chemistry*; D005697:Galactosides / Q000138:chemical synthesis* / Q000737:chemistry; D006031:Glycosylation; D017646:Organosilicon Compounds / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D005663:Furans; D005697:Galactosides; D017646:Organosilicon Compounds