title: Synthesis of non-glycosidic 4,6'-thioether-linked disaccharides as hydrolytically stable glycomimetics.
abstract: Michael addition of 1,2:3,4-di-O-isopropylidene-6-thio-alpha-D-galactose (2) to 2-propyl 6-O-acetyl-3,4-dideoxy-alpha-D-glycero-hex-3-enopyranosid-2-ulose (1) afforded, as the major diastereoisomer, 2-propyl 6-O-acetyl-3-deoxy-4-S-(6-deoxy-1,2:3,4-di-O-isopropylidene-alpha-D-galactopyranos-6-yl)-4-thio-alpha-D-threo-hexopyranosid-2-ulose (3, 91% yield). Reduction of the carbonyl group of 3, followed by O-deacetylation gave the two epimers 7 (alpha-D-lyxo) and 8 (alpha-D-xylo) in a 1:2 ratio. On removal of the protecting groups of 8 by acid hydrolysis, formation of an 1,6-anhydro bridge was observed in the 3-deoxy-4-thiohexopyranose unit (10). The free non-glycosidic thioether-linked disaccharide 3-deoxy-4-S-(6-deoxy-alpha,beta-D-galactopyranos-6-yl)-4-thio-alpha,beta-D-xylo-hexopyranose (11) was obtained by acetolysis of 10 followed by O-deacetylation. A similar sequence starting from the enone 1 and methyl 2,3,4-tri-O-benzoyl-6-thio-alpha-D-glucopyranoside (12) led successfully to 2-propyl 3-deoxy-4-S-(methyl 6-deoxy-alpha-D-glucopyranos-6-yl)-4-thio-alpha-D-lyxo-hexopyranoside (17) and its alpha-D-xylo analog (19, major product). In this synthetic route, orthogonal sets of protecting groups were employed to preserve the configuration of both reducing ends and to avoid the formation of the 1,6-anhydro ring.
authors.affiliation: CIHIDECAR-CONICET, Depto. Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, Ciudad Universitaria, 1428 Buenos Aires, Argentina.
authors.forename: María Laura
authors.initials: ML
authors.lastname: Uhrig
authors.forename: László
authors.initials: L
authors.lastname: Szilágyi
authors.forename: Katalin E
authors.initials: KE
authors.lastname: Kövér
authors.forename: Oscar
authors.initials: O
authors.lastname: Varela
mesh_terms: D002236:Carbohydrate Conformation; D004187:Disaccharides / Q000138:chemical synthesis* / Q000737:chemistry*; D006027:Glycosides; D007004:Hypoglycemic Agents / Q000737:chemistry; D008958:Models, Molecular; D013440:Sulfides
chemical_list: D004187:Disaccharides; D006027:Glycosides; D007004:Hypoglycemic Agents; D013440:Sulfides; C510695:coyolosa