title: Efficient synthesis of building blocks for branched rhamnogalacturonan I fragments.
abstract: Starting from allyl 2-O-acetyl-3-O-benzyl-α-l-rhamnopyranoside (3), allyl (2,3,4,6-tetra-O-benzoyl-β-d-galactopyranosyl)-(1→4)-2-O-acetyl-3-O-benzyl-α-l-rhamnopyranoside (5) was synthesized under Helferich conditions. Module 5 was converted to 2,3,4,6-tetra-O-benzoyl-β-d-galactopyranosyl-(1→4)-2-O-acetyl-3-O-benzyl-α-l-rhamnopyranosyl bromide (8) which was then coupled with methyl (allyl 2,3-di-O-benzyl-β-d-galactopyranosid)uronate (11) to provide methyl (2,3,4,6-tetra-O-benzoyl-β-d-galactopyranosyl)-(1→4)-(2-O-acetyl-3-O-benzyl-α-l-rhamnopyranosyl)-(1→4)-(allyl 2,3-di-O-benzyl-β-d-galactopyranosid)uronate (14). Alternatively, module 5 was transformed into allyl 2,3,4,6-tetra-O-benzoyl-β-d-galactopyranosyl-(1→4)-3-O-benzyl-α-l-rhamnopyranoside (9) suitable as an acceptor for the glycosylation with methyl 4-O-acetyl-2,3-di-O-benzyl-α/β-d-galactopyranosyluronate N-phenyl trifluoroacetimidate (13) to yield allyl (methyl 4-O-acetyl-2,3-di-O-benzyl-α-d-galactopyranosyluronate)-(1→2)-[2,3,4,6-tetra-O-benzoyl-β-d-galactopyranosyl]-(1→4)-3-O-benzyl-α-l-rhamnopyranoside (15). Both trisaccharides modules are suitable for the synthesis of branched pectin fragments.
authors.affiliation: University of Rostock, Institute of Chemistry, Albert-Einstein-Strasse 3a, D-18059 Rostock, Germany.
authors.forename: Amayak
authors.initials: A
authors.lastname: Pogosyan
authors.forename: Andreas
authors.initials: A
authors.lastname: Gottwald
authors.forename: Dirk
authors.initials: D
authors.lastname: Michalik
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Endress
authors.forename: Christian
authors.initials: C
authors.lastname: Vogel
mesh_terms: D002240:Carbohydrate Sequence; D060326:Chemistry Techniques, Synthetic; D005690:Galactose / Q000737:chemistry; D008969:Molecular Sequence Data; D010368:Pectins / Q000138:chemical synthesis* / Q000737:chemistry*; D013329:Structure-Activity Relationship
chemical_list: C042491:rhamnogalacturonan I; D010368:Pectins; D005690:Galactose
keywords: Glycosylation; Oligosaccharides; Pectin fragments; d-Galactosyl-l-rhamnose building block; d-Galacturonate N-phenyl trifluoroacetimidate