Divalent Sialylated Precision Glycooligomers Binding to Polyomaviruses and the Effect of Different Linkers.

Divalent precision glycooligomers terminating in N-acetylneuraminic acid (Neu5Ac) or 3'-sialyllactose (3'-SL) with varying linkers between scaffold and the glycan portions are synthesized via solid phase synthesis for co-crystallization studies with the sialic acid-binding major capsid protein VP1 of human Trichodysplasia spinulosa-associated Polyomavirus. High-resolution crystal structures of complexes demonstrate that the compounds bind to VP1 depending on the favorable combination of carbohydrate ligand and linker. It is found that artificial linkers can replace portions of natural carbohydrate linkers as long as they meet certain requirements such as size or flexibility to optimize contact area between ligand and receptor binding sites. The obtained results will influence the design of future high affinity ligands based on the structures presented here, and they can serve as a blueprint to develop multivalent glycooligomers as inhibitors of viral adhesion.

Synthesis of highly controlled carbohydrate-polymer based hybrid structures by combining heparin fragments and sialic acid derivatives, and solid phase polymer synthesis.

Heparin is a polymeric carbohydrate with a variety of biomedical applications that is particularly challenging from a synthetic point of view. Here, we present the synthesis of carbohydrate-polymer based hybrid structures by combining defined heparin fragments with monodisperse, sequence-controlled glycooligo(amidoamines) suitable as glycan mimetic model compounds of heparin as demonstrated by STD-NMR binding studies with viral capsids.

Split-and-Combine Approach Towards Branched Precision Glycomacromolecules and Their Lectin Binding Behavior.

Previously, monodisperse and sequence-controlled oligo(amidoamine) scaffolds were synthesized based on the step-wise assembly of tailor-made building blocks on a solid support that allow for the multivalent presentation of sugar ligands. Here, we extend on this concept using a split-and-combine approach to gain access to a small library of linear and branched glycomacromolecules. Azide side chains were introduced in the scaffold by the use of a novel building block allowing for copper-mediated azide-alkyne cycloaddition (CuAAC) of readily available propargyl-functionalized glycans. In the first stage, after assembly of the linear scaffold on solid support, the batch was divided into two. One part of the resin-bound oligomers was end-capped and further used as backbone and the other part was functionalized with propargylated α-d-mannopyranoside in the sidechain, end capped with an alkyne functionality and finally cleaved from solid support to give the branching arm. In the second stage, the linear, glycosylated and alkynylated arms were then coupled to the end capped backbone via CuAAC. In this way, branched glycomacromolecules with two and three branches, respectively, have been synthesized carrying from two to six sugar residues per molecule. Both, linear arms and branched glycomacromolecules were then subjected to a lectin binding assay using surface plasmon resonance (SPR) and model lectin Concanavalin A (Con A) showing the effect of branching as well as valency on the binding kinetics.

Cu Elimination from Cu-Coordinating Macromolecules.

We demonstrate a simple, fast, and efficient process for the elimination of Cu impurities from water-soluble Cu-coordinating macromolecules that are difficult to purify via standard polymer purification techniques. The process is based on the complexation and precipitation of Cu by sodium diethyldithiocarbamate and was investigated for two different compound classes known to coordinate to Cu in aqueous solution. More than 99.9% of the Cu impurity was eliminated, with a remaining level below the detection limit (0.0005 wt %). Further analysis by 1H NMR, MALDI, ATR-IR, and SEC showed no degradation or side reactions of the polymers induced by the treatment. This process thus compliments the growing toolbox of Cu-catalyzed conjugation techniques as a mild, effective, and scalable tool for the removal of Cu from water-soluble and Cu-coordinating polymers.