A versatile approach for the synthesis of sequence-controlled multiblock copolymers, using a combination of solid phase synthesis and step-growth polymerization by photoinduced thiol-ene coupling (TEC) is presented. Following this strategy, a series of sequence-controlled glycopolymers is derived from the polymerization of a hydrophilic spacer macromonomer and different glycomacromonomers bearing between one to five α-d-Mannose (Man) ligands. Through the solid phase assembly of the macromonomers, the number and positioning of spacer and sugar moieties is controlled and translates into the sequence-control of the final polymer. A maximum M̅ of 16 kDa, corresponding to a X̅ of 10, for the applied macromonomers is accessible with optimized polymerization conditions. The binding behavior of the resulting multiblock glycopolymers toward the model lectin Concanavalin A (ConA) is studied via turbidity assays and surface plasmon resonance (SPR) measurements, comparing the ability of precision glycomacromolecules and glycopolymers to bind to and cross-link ConA in dependence of the number of sugar moieties and overall molecular weight. The results show that there is a clear correlation between number of Man ligands and Con A binding and clustering, whereas the length of the glycooligomer- or polymer backbone seems to have no effect.
Supramolecular acid–acid interactions lead to competing monomeric and dimeric pathways in phosphoric acid catalysis – so that stereoselectivities depend on catalyst concentration.
Heterobifunctional rotaxanes serve as efficient catalysts for the addition of malonates to Michael acceptors. We report a series of four different heterobifunctional rotaxanes, featuring an amine‐based thread and a chiral 1,1′‐binaphthyl‐phosphoric‐acid‐based macrocycle. High‐level DFT calculations provided mechanistic insights and enabled rational catalyst improvements, leading to interlocked catalysts that surpass their non‐interlocked counterparts in terms of reaction rates and stereoselectivities.
A series of covalently linked bis‐ and trisphosphoric acids was investigated for their application in the stereoselective transfer‐hydrogenation of quinolines. In a combined experimental and theoretical study, it was found that the number and relative positioning of the chiral 1,1′‐binaphthyl‐phosphoric acid groups strongly influences the stereoselectivity of the reaction, based on two competing reaction mechanisms. While a single 3‐monosubstituted phosphoric acid moiety gives rise to little enantioselectivity, correct positioning of two phosphoric acids allows a cooperative mechanism, resulting in significantly higher stereoselectivities.
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