Crystal structure of 5-benzyl-8-bromo-2-meth-yl-1,3-oxazolo[4,5-c][1,8]naphthyridin-4(5H)-one.

The title compound, C17H12BrN3O2, was unexpectedly isolated during an attempt to synthesize pyridodiazepinediones and identified as an oxazolonaphthyridinone derivative. The almost planar oxazolonaphthyridinone ring (r.m.s. deviation = 0.016 Å) makes a dihedral angle of 61.6 (2)° with the phenyl ring. In the crystal, columns of mol-ecules stacked along the a axis are formed by π-π inter-actions between the six-membered rings of the oxazolonaphthyridone moieties [centroid-to-centroid distances = 3.494 (2)-3.906 (3) Å], which further inter-act through C-H⋯π contacts with the phenyl rings

The effect of prolyl oligopeptidase inhibitors on alpha-synuclein aggregation and autophagy cannot be predicted by their inhibitory efficacy

Previous studies have shown that prolyl oligopeptidase (PREP) negatively regulates autophagy and increases the aggregation of alpha-synuclein (alpha Syn), linking it to the pathophysiology of Parkinson's disease. Our earlier results have revealed that the potent small molecular PREP inhibitor KYP-2047 is able to increase autophagy and decrease dimerization of alpha Syn but other PREP inhibitors have not been systematically studied for these two protein-protein interaction mediated biological functions of PREP. In this study, we characterized these effects for 12 known PREP inhibitors with IC50-values ranging from 0.2 nM to 1010 nM. We used protein-fragment complementation assay (PCA) to assess alpha Syn dimerization and Western Blot of microtubule-associated protein light chain 3B II (LC3B-II) and a GFP-LC3-RFP expressing cell line to study autophagy. In addition, we tested selected compounds in a cell-free alpha Syn aggregation assay, native gel electrophoresis, and determined the compound concentration inside the cell by LC-MS. We found that inhibition of the proteolytic activity of PREP did not predict decreased alpha Syn dimerization or increased autophagy, and we also confirmed that this result did not simply reflect concentration differences of the compounds inside the cell. Thus, PREP ligands regulate the effect of PREP on autophagy and alpha Syn aggregation through a conformational stabilization of the enzyme that is not equivalent to inhibiting its proteolytic activity.Peer reviewe

The Effect of Prolyl Oligopeptidase Inhibitors on Alpha-Synuclein Aggregation and Autophagy Cannot Be Predicted by Their Inhibitory Efficacy

Previous studies have shown that prolyl oligopeptidase (PREP) negatively regulates autophagy and increases the aggregation of alpha-synuclein (αSyn), linking it to the pathophysiology of Parkinson’s disease. Our earlier results have revealed that the potent small molecular PREP inhibitor KYP-2047 is able to increase autophagy and decrease dimerization of αSyn but other PREP inhibitors have not been systematically studied for these two protein-protein interaction mediated biological functions of PREP. In this study, we characterized these effects for 12 known PREP inhibitors with IC50-values ranging from 0.2 nM to 1010 nM. We used protein-fragment complementation assay (PCA) to assess αSyn dimerization and Western Blot of microtubule-associated protein light chain 3B II (LC3B-II) and a GFP-LC3-RFP expressing cell line to study autophagy. In addition, we tested selected compounds in a cell-free αSyn aggregation assay, native gel electrophoresis, and determined the compound concentration inside the cell by LC-MS. We found that inhibition of the proteolytic activity of PREP did not predict decreased αSyn dimerization or increased autophagy, and we also confirmed that this result did not simply reflect concentration differences of the compounds inside the cell. Thus, PREP ligands regulate the effect of PREP on autophagy and αSyn aggregation through a conformational stabilization of the enzyme that is not equivalent to inhibiting its proteolytic activity.</p

Scaffold hopping from privileged diazepine derivatives towards novel tricyclic motifs

While the benzodiazepine drug class has been amongst the most prescribed medication globally since its discovery in the 1950s, the search for structurally related biologically active compounds is of major relevance to the pharmaceutical industry. In previous work in our group, we made the serendipitous finding that diazepinedione systems can undergo a rearrangement reaction, giving rise to completely new molecules with potentially interesting biological activities. These biological activities include antitumor, antimalarial, antibacterial, and central nervous system activities. In the latter case, the compounds could potentially be used in the treatment of anxiety and sleep disorders, and for the enhancement of memory. Owing to their evidently privileged topology, we have aimed to contribute to the synthetic repertoire for the preparation of both this particular class of promising scaffolds, and closely related scaffolds. Two different approaches have been developed for the preparation of these tricyclic motifs. In a first approach, annulated diazepinedione precursors were subjected to optimized rearrangement conditions to yield their corresponding tricyclic derivatives. In a second approach, tricyclic motifs were constructed by assembling the pivot heterocycle in a (3+3) cyclocondensation fashion. The key synthetic steps in the latter approach are: (1) the construction of a challenging amide linker connecting the two peripheral heterocycles; and (2) a palladium-catalyzed intramolecular C-H arylation event to form the key heterocycle. Both approaches make use of readily available starting materials. Throughout the synthetic explorations in this dissertation, continuous flow chemistry was adopted as enabling laboratory technique, and several flow protocols were developed with a much wider applicability than just our target molecules. This includes an efficient reaction protocol for the conversion of benzodiazepine materials into promising tricyclic derivatives, as well as a fast and efficient protocol for the formation of amides from low nucleophilic amines and esters. The final result was a successful preparation of the [1,3]oxazolo[4,5-c]-quinolin-4(5H)-one scaffold and the four isomeric [1,3]oxazolo[4,5-c]-1-naphthyridin-4(5H)-one scaffolds, in all cases allowing for the introduction of relevant points of diversity into the tricyclic products.status: publishe