Abstract:Recently, the strategy of multivalency has been widely employed to design glycosidase inhibitors, as glycomimetic clusters often induce marked enzyme inhibition relative to monovalent analogs. Polyhydroxylated pyrrolidines, one of the most studied classes of iminosugars, are an attractive moiety due to their potent and specific inhibition of glycosidases and glycosyltransferases, which are associated with many crucial biological processes. The development of multivalent pyrrolidine derivatives as glycosidase i… Show more
Multivalency represents an appealing option to modulate selectivity in enzyme inhibition and transform moderate glycosidase inhibitors into highly potent ones. The rational design of multivalent inhibitors is however challenging because global affinity enhancement relies on several interconnected local mechanistic events, whose relative impact is unknown. So far, the largest multivalent effects ever reported for a non‐polymeric glycosidase inhibitor have been obtained with cyclopeptoid‐based inhibitors of Jack bean α‐mannosidase (JBα‐man). Here, we report a structure‐activity relationship (SAR) study based on the top‐down deconstruction of best‐in‐class multivalent inhibitors. This approach provides a valuable tool to understand the complex interdependent mechanisms underpinning the inhibitory multivalent effect. Combining SAR experiments, binding stoichiometry assessments, thermodynamic modelling and atomistic simulations allowed us to establish the significant contribution of statistical rebinding mechanisms and the importance of several key parameters, including inhitope accessibility, topological restrictions, and electrostatic interactions. Our findings indicate that strong chelate‐binding, resulting from the formation of a cross‐linked complex between a multivalent inhibitor and two dimeric JBα‐man molecules, is not a sufficient condition to reach high levels of affinity enhancements. The deconstruction approach thus offers unique opportunities to better understand multivalent binding and provides important guidelines for the design of potent and selective multiheaded inhibitors.
Multivalency represents an appealing option to modulate selectivity in enzyme inhibition and transform moderate glycosidase inhibitors into highly potent ones. The rational design of multivalent inhibitors is however challenging because global affinity enhancement relies on several interconnected local mechanistic events, whose relative impact is unknown. So far, the largest multivalent effects ever reported for a non‐polymeric glycosidase inhibitor have been obtained with cyclopeptoid‐based inhibitors of Jack bean α‐mannosidase (JBα‐man). Here, we report a structure‐activity relationship (SAR) study based on the top‐down deconstruction of best‐in‐class multivalent inhibitors. This approach provides a valuable tool to understand the complex interdependent mechanisms underpinning the inhibitory multivalent effect. Combining SAR experiments, binding stoichiometry assessments, thermodynamic modelling and atomistic simulations allowed us to establish the significant contribution of statistical rebinding mechanisms and the importance of several key parameters, including inhitope accessibility, topological restrictions, and electrostatic interactions. Our findings indicate that strong chelate‐binding, resulting from the formation of a cross‐linked complex between a multivalent inhibitor and two dimeric JBα‐man molecules, is not a sufficient condition to reach high levels of affinity enhancements. The deconstruction approach thus offers unique opportunities to better understand multivalent binding and provides important guidelines for the design of potent and selective multiheaded inhibitors.
This account describes our recent studies in the field of glycomimetics. Our efforts in understanding the structural basis of multivalent effects in glycosidase inhibition have led to decisive mechanistic insights supported by X-ray diffraction analyses and to the discovery of multimeric iminosugars displaying one of the largest binding enhancements reported so far for a non-polymeric enzyme inhibitor. Pushing the limits of the inhibitory multivalent effect has also driven progress in synthetic methodology. The unexpected observation of side products en route to the synthesis of our targets has been the starting point of several new synthetic methodologies, including metal-free deoxygenation of alcohols and one-pot double thioglycosylation. In parallel to our work on ‘giant’ neoglycoclusters, we have developed access to original constrained glycomimetics based on a 4-membered ring (‘square sugars’). Carbohydrates with a quaternary (pseudo)anomeric position were also synthesized from exo-glycals through catalytic hydrogen atom transfer and a novel oxidative radical-polar crossover process.1 Introduction2 Sweet Giants3 Multivalency Spin-Offs4 Sweet Curiosities4.1 Square Sugars4.2 From C,C-Glycosides to Formal Glycosylation of Quinones5 Conclusion
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