ß-Sultams exhibit discrete binding preferences for diverse bacterial enzymes with nucleophilic residues.

ß-Sultams are potent electrophiles that modify nucleophilic residues in selected enzyme active sites. We here identify and characterize some of the specific bacterial targets and show a unique inhibition of the azoreductase family.

Disruption of oligomerization and dehydroalanine formation as mechanisms for ClpP protease inhibition.

Over 100 protease inhibitors are currently used in the clinics, and most of them use blockage of the active site for their mode of inhibition. Among the protease drug targets are several enzymes for which the correct multimeric assembly is crucial to their activity, such as the proteasome and the HIV protease. Here, we present a novel mechanism of protease inhibition that relies on active-site-directed small molecules that disassemble the protease complex. We show the applicability of this mechanism within the ClpP protease family, whose members are tetradecameric serine proteases and serve as regulators of several cellular processes, including homeostasis and virulence. Compound binding to ClpP in a substoichiometric fashion triggers the formation of completely inactive heptamers. Moreover, we report the selective ß-sultam-induced dehydroalanine formation of the active site serine. This reaction proceeds through sulfonylation and subsequent elimination, thereby obliterating the catalytic charge relay system. The identity of the dehydroalanine was confirmed by mass spectrometry and crystallography. Activity-based protein profiling experiments suggest the formation of a dehydroalanine moiety in living S. aureus cells upon ß-sultam treatment. Collectively, these findings extend our view on multicomponent protease inhibition that until now has mainly relied on blockage of the active site or occupation of a regulatory allosteric site.

Tailoring of integrin ligands: probing the charge capability of the metal ion-dependent adhesion site.

Intervention in integrin-mediated cell adhesion and integrin signaling pathways is an ongoing area of research in medicinal chemistry and drug development. One key element in integrin-ligand interaction is the coordination of the bivalent cation at the metal ion-dependent adhesion site (MIDAS) by a carboxylic acid function, a consistent feature of all integrin ligands. With the exception of the recently discovered hydroxamic acids, all bioisosteric attempts to replace the carboxylic acid of integrin ligands failed. We report that phosphinates as well as monomethyl phosphonates represent excellent isosters, when introduced into integrin antagonists for the platelet integrin αIIbß3. The novel inhibitors exhibit in vitro and ex vivo activities in the low nanomolar range. Steric and charge requirements of the MIDAS region were unraveled, thus paving the way for an in silico prediction of ligand activity and in turn the rational design of the next generation of integrin antagonists.

Radical arylation of phenols, phenyl ethers, and furans.

Radical arylations of para-substituted phenols and phenyl ethers proceeded with good regioselectivity at the ortho position with respect to the hydroxy or alkoxy group. The reactions were conducted with arenediazonium salts as the aryl radical source, titanium(III) chloride as the reductant, and diluted hydrochloric acid as the solvent. Substituted biaryls were obtained from hydroxy- and alkoxy-substituted benzylamines, phenethylamines, and aromatic amino acids. The methodology described offers a fast, efficient, and cost-effective new access to diversely functionalized biphenyl alcohols and ethers. Free phenolic hydroxy groups, aromatic and aliphatic amines, as well as amino acid substructures, are well tolerated. Two examples for the applicability of the methodology are the partial synthesis of a beta-secretase inhibitor and the synthesis of a calcium-channel modulator.