Enhancing the enthalpic contribution of hydrogen bonds by solvent shielding.

In biological systems, polar interactions are heavily burdened by high desolvation penalties resulting from strong solute-solvent interactions. As a consequence thereof, enthalpic contributions of hydrogen bonds to the free energy of binding are severely diminished. However, this effect is strongly attenuated for interactions within solvent-shielded areas of proteins. In microcalorimetric experiments, we show that the bacterial lectin FimH utilizes conformational adaptions to effectively shield its binding site from solvent. The transition into a lower dielectric environment results in an enthalpic benefit of approximately -13 kJ mol-1 for mannoside binding. However, this effect can be abrogated, if the hydrogen bond network within the binding site is disturbed by deoxygenation of the ligand. Conformational adaption leading to reduced local dielectric constants could represent a general mechanism for proteins to enable enthalpy-driven recognition of polar ligands.

Improvement of Aglycone π-Stacking Yields Nanomolar to Sub-nanomolar FimH Antagonists.

Antimicrobial resistance has become a serious concern for the treatment of urinary tract infections. In this context, an anti-adhesive approach targeting FimH, a bacterial lectin enabling the attachment of E. coli to host cells, has attracted considerable interest. FimH can adopt a low/medium-affinity state in the absence and a high-affinity state in the presence of shear forces. Until recently, mostly the high-affinity state has been investigated, despite the fact that a therapeutic antagonist should bind predominantly to the low-affinity state. In this communication, we demonstrate that fluorination of biphenyl α-d-mannosides leads to compounds with perfect π-π stacking interactions with the tyrosine gate of FimH, yielding low nanomolar to sub-nanomolar KD values for the low- and high-affinity states, respectively. The face-to-face alignment of the perfluorinated biphenyl group of FimH ligands and Tyr48 was confirmed by crystal structures as well as 1 H,15 N-HSQC NMR analysis. Finally, fluorination improves pharmacokinetic parameters predictive for oral availability.

Glucosylceramide mimics: highly potent GCase inhibitors and selective pharmacological chaperones for mutations associated with types†1 and 2 Gaucher disease.

A series of iminoxylitol derivatives carrying a C-linked di-O-acyl or di-O-alkyl glyceryl substituent were prepared and characterized. All of these compounds, which were designed as glucosylceramide (GlcCer) mimics, were nanomolar inhibitors of lysosomal ß-glucosidase (glucocerebrosidase, GCase). Two of these pseudoglycolipids were further evaluated for their ability to enhance the activity of mutant GCase in human Gaucher cells. Although the di-O-hexyl ether was surprisingly devoid of chaperoning activity on both N370S and L444P GCases, the di-O-decanoyl ester was a potent chaperone of the L444P hydrolase, capable of increasing the residual activity of the enzyme by a factor of two at a very low concentration (50 nM); such a significant effect on the L444P mutation in human fibroblasts has not yet been observed. In heat-stress studies, the diether was found to be much more effective in stabilizing the wild-type enzyme than the diester. Four representative pseudoglycolipids were also assayed as inhibitors of GlcCer synthase, because such compounds could find use in the substrate reduction therapy approach to treat lysosomal storage diseases, but these compounds revealed only moderate activity. As efficient pharmacological chaperones, new structures such as the di-C10 -ester constitute leads for the development of therapeutic agents for types 2 and 3 Gaucher disease, the most severe neuronopathic forms of this lysosomal disease.

Synthesis of new beta-1-C-alkylated imino-L-iditols: A comparative study of their activity as beta-glucocerebrosidase inhibitors.

A short synthesis of new beta-1-C-alkyl-1,5-dideoxy-1,5-imino-l-iditols by means of the diastereoselective addition of Grignard reagents onto a glucopyranosylamine is described. These compounds were evaluated as beta-glucocerebrosidase inhibitors and their activity was compared with that of related iminosugar derivatives in the d-gluco and d-xylo series. The results allowed us to conclude on the influence of the hydroxymethyl moiety and of the piperidine-ring conformation on the inhibitory activity.