title: Synthesis of linear beta-(1 --> 4)-galacto-hexa- and heptasaccharides and studies directed towards cyclogalactans.
abstract: Synthesis of an exclusively beta-(1 --> 4)-linked galactohexa- and heptasaccharide is described by coupling a 2-O-pivaloyl-3,6-O-allyl-protected thiogalactobioside donor with an equally protected, yet terminally 4-OH-free galactopentaoside. The same approach though failed to elaborate cyclic oligomers, as neither cyclodimerization of the correspondingly protected thiogalactotriosides with a 4"-OH could be effected, nor intramolecular glycosidation of the respective hexa- and heptagalactosides with an unprotected 4-OH at one, and phenylthio or sulfoxido groups at the reducing end. The causative factors underlying this are attributed to an inadequate predisposition of the linear beta-(1 --> 4)-galactan chains to adopt the tightly coiled molecular geometry necessary for cyclization--at least at the hexa- and heptasaccharide stage.
authors.affiliation: Institut für Organische Chemie, Technische Universität Darmstadt, Petersenstrasse 22, D-64287 Darmstadt, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Oberthür
authors.forename: Siegfried
authors.initials: S
authors.lastname: Peters
authors.forename: Saibal
authors.initials: S
authors.lastname: Kumar Das
authors.forename: Frieder W
authors.initials: FW
authors.lastname: Lichtenthaler
mesh_terms: D002236:Carbohydrate Conformation; D003500:Cyclization; D005685:Galactans / Q000138:chemical synthesis* / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D013862:Thiogalactosides
chemical_list: D005685:Galactans; D009844:Oligosaccharides; D013862:Thiogalactosides