INVESTIGADORES
GALLO Carola
congresos y reuniones científicas
Título:
A novel route of (1-5)-b-D-galactofuran derivatives by regioselective opening of 3,5-O-di-tert-butylsilylene-D-thiogalactofuranosides
Autor/es:
MARIANO J. TILVE; CAROLA GALLO -RODRIGUEZ
Lugar:
Oporto
Reunión:
Simposio; Terceiro simposio Iberoamericano de Química Orgánica (SIBEAQO III); 2016
Institución organizadora:
Universidad de Porto
Resumen:
Galactose in the furanose form is present in several pathogenic microorganisms whereas it is not biosynthesized by mammals. The synthesis of Galf-containing oligosaccharides has gained much attention as components of tools for studying their biological functions. It requires a first choice of the galactofuranosyl template, which has to be functionalized or protected, and this selection is deeply related to the method of glycosylation employed. The use of thiogalactofuranosides as donors for the construction of oligosaccharides containing internal Galf is limited. This fact could be attributed to the difficulty to functionalize thiogalactofuranoside derivatives showing O-2, O-3 and O-5 with similar reactivities. In view of our experience with 3,5-O-di-tert-butylsilylene-D-galactofuranosyl derivatives,1,2 the differentiation between the secondary hydroxyl groups 3-OH and 5-OH was envisioned. An efficient method for complete regioselective 5-O-opening of 3,5-O-di-tert-butylsilylene-D-galactofuranoside derivatives was developed. The use of a solution nBu4NF (1.1 equiv) in CH2Cl2 on 3,5-O-DTBS derivative 1 gave the 5-OH derivative 2 which was confirmed by acetylation. 3-O-Di-tert-butylhydroxysilyl derivative 2 was a stable compound after purification and under glycosylation reactions. Preactivation of conformationally restricted thioglycoside 1 employing p-NO2-benzensulfenyl chloride/AgOTf promoting system3 followed by condensation over the 5-OH thioglycoside derivative product 2 gave the disaccharide 3 without autocondensation by-product. The disaccharide 3 was also used as a donor to afford the corresponding trisaccharide 4. Moreover, regioselective 5-O-deprotection was also successfully performed on disaccharide 3 and trisaccharide 4
