Bacterial resistance is increasing rapidly, requiring urgent identification of new antibacterial drugs that are effective against multidrug-resistant pathogens. Novel bacterial topoisomerase inhibitors (NBTIs) provide a new strategy for investigating the well-validated DNA gyrase and topoisomerase IV targets while preventing cross-resistance issues. On this basis, starting from a virtual screening campaign and subsequent structure-based hit optimization guided by X-ray studies, a novel class of piperazine-like NBTIs with outstanding enzymatic activity against Staphylococcus aureus and Escherichia coli DNA gyrase and topoisomerase IV was identified. Notably, compounds (±)-33, (±)-35, and (±)-36 with potent and balanced multitarget enzymatic profiles exhibited excellent efficacy against selected Gram-positive and Gram-negative pathogens, as well as clinically relevant resistant strains. Overall, the new NBTI chemotype described herein, owing to the broad-spectrum antibacterial activity and favorable in vitro safety profile, might serve as a basis for the development of novel treatments against serious infections.

An expeditious preparation of the 6-exo-hydroxybicyclo[2.2.2]octan-2-one ethylene dithioacetal 2b, a key intermediate in the synthesis of (þ)-13-stemarene (4) and (þ)-18-deoxystemarin (5) is described. Compound 2b was obtained as the major product by equilibrating the endo rich mixture of 6-hydroxybicyclo[2.2.2]octan-2-one ethylene dithioacetals 2 with TsOH in benzene at reflux, easily available from the corresponding hydroxy ketones 9. The model experiments which preceeded the above transformation, not previously described in the literature, are also presented.Introduction. By Raney-Ni desulfurization, hydroxydithioacetals 1 and 2b were in fact transformed into bicyclo[2.2.2]octan-2-ols 6 and 7, and the latter rearranged 3 ) to the stemarane system (Scheme 1).Compounds 1 and 2b were efficiently prepared from the corresponding 6-exohydroxybicyclo[2.2.2]octan-2-ones 8 and 9b by thioacetalization with 1,2-ethanedithiol in the presence of BF 3 · Et 2 O [2] [6]. Given that 6-exo-hydroxybicyclo[2.2.2]octan-2-ones of the type of 8 and 9b are the minor products (endo/exo 85 : 15) of the intramolecular aldol condensation of a 3-oxocyclohexaneacetaldehyde [7] [8] (Scheme 2), the efficiency of the synthesis of stemarane diterpenoids, by this approach,

Microsomal prostaglandin E synthase-1 (mPGES-1) constitutes an inducible glutathione-dependent integral membrane protein that catalyzes the oxido-reduction of cyclooxygenase derived PGH₂ into PGE₂. mPGES-1 is an essential enzyme involved in a variety of human diseases or pathological conditions, such as rheumatoid arthritis, fever, and pain; it is therefore regarded as a primary target for development of next-generation anti-inflammatory drugs. Several compounds targeting human mPGES-1 have been reported in the literature. However, none of them is really specific for mPGES-1, and quite surprisingly, all of these compounds have very low or no activity against murine mPGES-1, making preclinical development hard and very expensive. In order to overcome this unresolved question, the current study focuses on the elucidation of the molecular determinants of murine mPGES-1 ligand binding modes combining protein homology modeling and site-directed mutagenesis approaches. We have developed, for the first time, two murine mPGES-1 models, describing both the closed and the open/active conformation of the enzyme. The 3D structure of human mPGES-1 having been recently disclosed, the main differences between the human and the murine enzyme models are described, emphasizing the smaller dimensions of the rodent substrate binding site, which could account for different activity of a ligand toward the two species. Furthermore, active binding modes are hypothesized, highlighting the most likely important residues for inhibition activity, whose identification is supported by in-house mutagenesis experiments. The results of our work could provide grounds for a rational structure-based drug design aimed to identify new inhibitors active against both human and murine mPGES-1.