Potential peptidic proteasome inhibitors by incorporation of an electrophilic trap based on amino acid derived α-substituted sulfonyl fluorides

Peptido sulfonyl fluoride derivatives were designed and synthesized containing a substituent on the alpha position (αPSFs) with respect to the sulfonyl fluoride electrophilic trap. The chemical reactivity of these α-substituted amino sulfonyl fluorides was studied and compared with the previously described β-substituted amino sulfonyl fluorides in order to get a deeper insight into the importance of the immediate structural environment of the sulfonyl fluoride moiety. Unfortunately, the poor solubility of the resulting αPSFs precluded a proper evaluation of their biological activity

Proteasome inhibition by new dual warhead containing peptido vinyl sulfonyl fluorides

The success of inhibition of the proteasome by formation of covalent bonds is a major victory over the long held-view that this would lead to binding the wrong targets and undoubtedly lead to toxicity. Great challenges are now found in uncovering ensembles of new moieties capable of forming long lasting ties. We have introduced peptido sulfonyl fluorides for this purpose. Tuning the reactivity of this electrophilic trap may be crucial for modulating the biological action. Here we describe incorporation of a vinyl moiety into a peptido sulfonyl fluoride backbone, which should lead to a combined attack of the proteasome active site threonine on the double bond and the sulfonyl fluoride. Although this led to strong proteasome inhibitors, in vitro studies did not unambiguously demonstrate the formation of the proposed seven-membered ring structure. Possibly, formation of a seven-membered covalent adduct with the proteosomal active site threonine can only be achieved within the context of the enzyme. Nevertheless, this dual warhead concept may provide exclusive possibilities for duration and selectivity of proteasome inhibition

Potent and highly selective inhibitors of the proteasome trypsin-like site by incorporation of basic side chain containing amino acid derived sulfonyl fluorides

A unique category of basic side chain containing amino acid derived sulfonyl fluorides (SFs) has been synthesized for incorporation into new proteasome inhibitors targeting the trypsin-like site of the 20S proteasome. Masking the former α-amino functionality of the amino acid starting derivatives as an azido functionality allowed an elegant conversion to the corresponding amino acid derived sulfonyl fluorides. The inclusion of different SFs at the P1 site of a proteasome inhibitor resulted in 14 different peptidosulfonyl fluorides (PSFs) having a high potency and an excellent selectivity for the proteolytic activity of the β2 subunit over that of the β5 subunit. The results of this study strongly indicate that a free N-terminus of PSFs inhibitors is crucial for high selectivity toward the trypsin-like site of the 20S proteasome. Nevertheless, all compounds are slightly more selective for inhibition of the constitutive over the immunoproteasome

Targeted Covalent Inhibition of Prolyl Oligopeptidase (POP): Discovery of Sulfonylfluoride Peptidomimetics

Prolyl oligopeptidase (POP), a serine protease highly expressed in the brain, has recently emerged as an enticing therapeutic target for the treatment of cognitive and neurodegenerative disorders. However, most reported inhibitors suffer from short duration of action, poor protease selectivity, and low blood-brain barrier (BBB) permeability, which altogether limit their potential as drugs. Here, we describe the structure-based design of the first irreversible, selective, and brain-permeable POP inhibitors. At low-nanomolar concentrations, these covalent peptidomimetics produce a fast, specific, and sustained inactivation of POP, both in vitro and in human cells. More importantly, they are >1,000-fold selective against two family-related proteases (DPPIV and FAP) and display high BBB permeability, as shown in both lipid membranes and MDCK cells

Synthesis of monophosphoryl lipid A using 2-naphtylmethyl ethers as permanent protecting groups

Lipid A, which is a conserved component of lipopolysaccharides of gram-negative bacteria, has attracted considerable interest for the development of immuno-adjuvants. Most approaches for lipid A synthesis rely on the use of benzyl ethers as permanent protecting groups. Due to the amphiphilic character of lipid A, these compounds aggregate during the hydrogenation step to remove benzyl ethers, resulting in a sluggish reaction and by-product formation. To address this problem, we have developed a synthetic approach based on the use of 2-naphtylmethyl ether (Nap) ethers as permanent protecting group for hydroxyls. At the end of a synthetic sequence, multiple of these protecting groups can readily be removed by oxidation with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ). Di-allyl N,N-diisopropylphosphoramidite was employed to install the phosphate ester and the resulting allyl esters were cleaved using palladium tetrakistriphenylphosphine. The synthetic strategy allows late stage introduction of different fatty acids at the amines of the target compound, which is facilitated by Troc and Fmoc as orthogonal amino-protecting groups

Expedient synthesis of a novel asymmetric selectively deprotectable derivative of the ATAC scaffold

An efficient multigram scale synthesis of a new asymmetric triazacyclophane scaffold, the ATAC (Asymmetric-TAC) scaffold, bearing three selectively removable groups is described. This scaffold is slightly more rigid than our frequently used TAC (TriAzaCyclophane) scaffold. The synthesis of the required triamine is very high yielding without difficult steps or purifications and was also applied to a much improved synthesis of our original TAC scaffold. Especially the tedious first reaction step, that is, mono-oNBS-protection of a triamine could be omitted. The rigidity of the triazacyclophane ring in both TAC- and ATAC scaffolds has also been investigated using variable temperature 1H NMR experiments

Change in the financial sector and trends in housing finance markets

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Delayed fibril formation of amylin(20-29) by incorporation of alkene dipeptidosulfonamide isosteres obtained by solid phase olefin cross metathesis

The synthesis of a new peptidomimetic structure, the alkene dipeptidosulfonamide isostere, is described. The synthesis is based on a cross metathesis reaction between two allylic building blocks, both in solution and on the solid phase. This method was also applicable to the solid phase synthesis of alkene dipeptide isosteres. Derivatives of amylin(20-29) containing the alkene dipeptidosulfonamide isostere as well as the alkene dipeptide isostere were successfully synthesized using the solid phase cross metathesis method. Investigation of relations between structure and fibril formation of these amylin(20-29) derivatives showed retardation of fibril formation and altered secondary structures, compared to native amylin(20-29). © 2007 Elsevier Ltd. All rights reserved