In the present work new coupling reagents (couplers) and N-acetylamino-2-deoxy-ß-D-glucosamine (GlcNAc) derivatives for the preparation of biofunctionalised hydrogel layers were designed. Aim was to develop a flexible tool box and a method for immobilisation of glycanes, which are of interest for glycobiology, implant coatings and diagnostic applications.
On the basis of trimethylolpropane two 6-membered ring carbonate couplers were prepared, which were substituted with reactive side groups: an imidazolyl carbamate and a phenyl carbonate. Their syntheses and characterisations are described and compared to known ring carbonate couplers from the literature. These couplers have two functional groups, which are highly reactive towards amines, never the less can be selectively addressed and therefore are useful for reactions under mild reaction conditions. Starting from these couplers two orthogonal reactive couplers were synthesized, which have a 6-membered ring carbonate and a propargyl or an azide reactive side group. These orthogonal couplers have highly reactive functional groups for conversion at mild reaction conditions. In a model reaction tert-butyl- N-(3-aminopropyl) carbamate was condensed with (5-ethyl-2-oxo-1,3-dioxan-5-yl)methyl prop-2-ynylcarbamate by an addition-reaction and 2-azidoethyl 2-N-acetylamino-2-deoxy-ß- D-glucopyranose was linked by a 1,3-dipolar cycloaddition.
This principle to connect two building blocks by a coupler was used for the preparation of multifunctional polymers or multifunctional surface coatings. Because of the mild reaction conditions temperature sensitive components can be used, too. Possible applications are the preparation of glycoconjugates like glycopolymers or glycoarrays. 5-Ethyl-5-((prop-2ynyloxy)methyl)-1,3-dioxan-2-one was synthesised in a 4-step-synthesis. This orthogonal reactive coupler was used to bind a biologically active N-acetylglucosamine azide to an amino-reactive microtiter plate and a microtiter plate, which was coated with a sP(EO-stat- PO) hydrogel layer. The biological activity of immobilised carbohydrates was determined using an enzyme-linked lectin assay (ELLA). It was shown, that this coupler binds N- acetylglucosamine azide on amino reactive substrates, without loss of the biological activity. This flexible immobilisation technique could be assign for glycanes known from literature. Hydrogel layers from sP(EO-stat-PO) are known for their ability to prevent biological adhesion on surfaces. Highly selective biofunctional hydrogel layers were prepared, which are interesting for glycobiology, implant coatings and diagnostic applications.
The reactivity of the presented couplers were investigated for the preparation of trifunctional couplers and the preparation of new poly(urethane)s with primary hydroxy groups in the side chain. The latter were synthesised from (5-ethyl-2-oxo-1,3-dioxan-5-yl)methyl phenyl carbonate and (5-ethyl-2-oxo-1,3-dioxan-5-yl)methyl imidazolyl carbonate with 1,2ethylenediamine, 1,4-butanediamine and 1,6-hexenediamine. These low molecular weight poly(hydroxyurethane) building blocks were characterised by SEC, DSC, TGA and by means of NMR and IR spectroscopy and the results were compared to previously reported results of PHUs prepared from phenoxycarbonyl-oxymethyl ethylene carbonate with the corresponding diamines.