title: Synthesis of AB4-type carbohydrate scaffolds as branching units in the glycosciences.
abstract: Carbohydrate scaffolds, functionalised according to an AB4-type, were prepared on the basis of α-D-mannopyranosides with various ethyl aglycone moieties, functionalised with 'A'. Four functional groups 'B' were installed at positions 2, 3, 4, and 6 of the sugar ring. In particular, we were interested in preparing N3(NH2)4-functionalised mannosides as multifunctional branching units for further orthogonal derivatisation or immobilisation on surfaces. A detailed synthetic study was performed which revealed that an azido function 'A' had to be installed at an advanced stage of the synthesis for successful preparation of the desired AB4-type carbohydrate scaffolds. The most successful synthetic sequence involved tetra-cyanoethylation of a 2-benzyloxyethyl mannopyranoside and subsequent reduction with in situ Boc protection to achieve (NHBoc)4 functionalisation. Finally, the benzyloxyethyl aglycon was converted into the corresponding azidoethyl moiety to gain access to the desired N3(NHBoc)4-functionalised carbohydrate scaffold. Its utilisation was exemplified by straightforward synthesis of a photosensitive glycoconjugate and a tetravalent glycocluster. Such compounds may be immobilised on functional surfaces to serve as tools in cell adhesion studies.
authors.affiliation: Otto Diels Institute of Organic Chemistry, Christiana Albertina University of Kiel, Otto-Hahn-Platz 3/4, Kiel D-24118, Germany.
authors.forename: Tobias-Elias
authors.initials: TE
authors.lastname: Gloe
authors.affiliation: Otto Diels Institute of Organic Chemistry, Christiana Albertina University of Kiel, Otto-Hahn-Platz 3/4, Kiel D-24118, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Müller
authors.affiliation: Otto Diels Institute of Organic Chemistry, Christiana Albertina University of Kiel, Otto-Hahn-Platz 3/4, Kiel D-24118, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Ciuk
authors.affiliation: Glycogroup, Institute of Organic Chemistry, Technical University Graz, Stremayrgasse 9, Graz A-8010, Austria.
authors.forename: Tanja M
authors.initials: TM
authors.lastname: Wrodnigg
authors.affiliation: Otto Diels Institute of Organic Chemistry, Christiana Albertina University of Kiel, Otto-Hahn-Platz 3/4, Kiel D-24118, Germany. Electronic address: tklind@oc.uni-kiel.de.
authors.forename: Thisbe K
authors.initials: TK
authors.lastname: Lindhorst
mesh_terms: D002241:Carbohydrates / Q000138:chemical synthesis* / Q000737:chemistry*; D015394:Molecular Structure
chemical_list: D002241:Carbohydrates
keywords: Glycoclusters; Octopus glycosides; Orthogonality, multivalency; Protecting groups