Synthesis and Lectin Recognition of Glyco Star Polymers Prepared by "Clicking" Thiocarbohydrates onto a Reactive Scaffold

Glycopolymers with a four-arm star architecture were prepared from poly(vinyl benzyl chloride) (PVBC) star polymers as reactive scaffold and 1-thio-beta-D-glucose sodium salt. The star polymer was prepared via RAFT polymerization using 1,2,4,5-tetrakis(thiobenzoylthiomethyl)benzene as a rate-retarding RAFT Latent at a polymerization temperature of 120 degrees C. The occurrence of known side reactions such as star-star coupling Was partly suppressed by optimizing the reaction conditions. The molecular weight distribution in the early stages of the polymerization (< 50% monomer conversion) remained narrow (PDI < 1.3), but side reaction became more pronounced at higher conversions. The polymers were reacted with equimolar amounts of 1-thio-beta-D-glucose sodium salt in DMSO in the absence of any catalyst. The rate of reaction was monitored using H-1 NMR, confirming full conversion alter a reaction time of 110 h. Six different glyco star polymers with number of repeating units N ranging from 40 to 680 were tested regarding their ability to bind to Concanavalin A (ConA) using turbidity assay. The rate of reaction and t(1/2), the time to reach half of the maximum absorption, was found to reach it maximum and minimum, respectively, at a medium molecular weight. The same molecular weight dependency was obtained using precipitation assay, which determines the amount of ConA conjugated to the glycopolymer. Comparison with linear glycopolymers reveals however that the amount of bound ConA and the rate of clustering are not superior in the star architecture.