Alessio Porta

Electrophilic Cyclopentenone Neuroprostanes Are Anti-inflammatory Mediators Formed from the Peroxidation of the ω-3 Polyunsaturated Fatty Acid Docosahexaenoic Acid

The ω-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) possesses potent anti-inflammatory properties and has shown therapeutic benefit in numerous inflammatory diseases. However, the molecular mechanisms of these anti-inflammatory properties are poorly understood. DHA is highly susceptible to peroxidation, which yields an array of potentially bioactive lipid species. One class of compounds are cyclopentenone neuroprostanes (A4/J4-NPs), which are highly reactive and similar in structure to anti-inflammatory cyclopentenone prostaglandins. Here we show that a synthetic A4/J4-NP, 14-A4-NP (A4-NP), potently suppresses lipopolysaccharideinduced expression of inducible nitric-oxide synthase and cyclooxygenase-2 in macrophages. Furthermore, A4-NP blocks lipopolysaccharide-induced NF-κB activation via inhibition of Iκ kinase-mediated phosphorylation of IκBα. Mutation on Iκ kinase β cysteine 179 markedly diminishes the effect of A4-NP, suggesting that A4-NP acts via thiol modification at this residue. Accordingly, the effects of A4-NP are independent of peroxisome proliferator-activated receptor-γ and are dependent on an intact reactive cyclopentenone ring. Interestingly, free radical-mediated oxidation of DHA greatly enhances its anti-inflammatory potency, an effect that closely parallels the formation of A4/J4-NPs. Furthermore, chemical reduction or conjugation to glutathione, both of which eliminate the bioactivity of A4-NP, also abrogate the anti-inflammatory effects of oxidized DHA. Thus, we have demonstrated that A4/J4-NPs, formed via the oxidation of DHA, are potent inhibitors of NF-κB signaling and may contribute to the anti-inflammatory actions of DHA. These findings have implications for understanding the anti-inflammatory properties of ω-3 fatty acids, and elucidate novel interactions between lipid peroxidation products and inflammation.

A Simple and Versatile Re‐Catalyzed Meyer–Schuster Rearrangement of Propargylic Alcohols to α,β‐Unsaturated Carbonyl Compounds

Rhenium does the job! A readily available rhenium complex efficiently catalyzed the direct Meyer-Schuster-like rearrangement of different alkyl- and aryl-substituted propargylic secondary and tertiary alcohols to the corresponding alpha,beta-unsaturated compounds, which were produced with virtually complete E stereoselectivity. The reaction proceeded under neutral conditions and no racemization of potentially enolizable stereocenters was observed.

2-Carboxyquinoxalines Kill Mycobacterium tuberculosis through Noncovalent Inhibition of DprE1

Phenotypic screening of a quinoxaline library against replicating Mycobacterium tuberculosis led to the identification of lead compound Ty38c (3-((4-methoxybenzyl)amino)-6-(trifluoromethyl)quinoxaline-2-carboxylic acid). With an MIC99 and MBC of 3.1 μM, Ty38c is bactericidal and active against intracellular bacteria. To investigate its mechanism of action, we isolated mutants resistant to Ty38c and sequenced their genomes. Mutations were found in rv3405c, coding for the transcriptional repressor of the divergently expressed rv3406 gene. Biochemical studies clearly showed that Rv3406 decarboxylates Ty38c into its inactive keto metabolite. The actual target was then identified by isolating Ty38c-resistant mutants of an M. tuberculosis strain lacking rv3406. Here, mutations were found in dprE1, encoding the decaprenylphosphoryl-d-ribose oxidase DprE1, essential for biogenesis of the mycobacterial cell wall. Genetics, biochemical validation, and X-ray crystallography revealed Ty38c to be a noncovalent, noncompetitive DprE1 inhibitor. Structure-activity relationship studies generated a family of DprE1 inhibitors with a range of IC50s and bactericidal activity. Co-crystal structures of DprE1 in complex with eight different quinoxaline analogs provided a high-resolution interaction map of the active site of this extremely vulnerable target in M. tuberculosis.

Thiophenecarboxamide Derivatives Activated by EthA Kill Mycobacterium tuberculosis by Inhibiting the CTP Synthetase PyrG.

Summary To combat the emergence of drug-resistant strains of Mycobacterium tuberculosis, new antitubercular agents and novel drug targets are needed. Phenotypic screening of a library of 594 hit compounds uncovered two leads that were active against M. tuberculosis in its replicating, non-replicating, and intracellular states: compounds 7947882 (5-methyl-N-(4-nitrophenyl)thiophene-2-carboxamide) and 7904688 (3-phenyl-N-[(4-piperidin-1-ylphenyl)carbamothioyl]propanamide). Mutants resistant to both compounds harbored mutations in ethA (rv3854c), the gene encoding the monooxygenase EthA, and/or in pyrG (rv1699) coding for the CTP synthetase, PyrG. Biochemical investigations demonstrated that EthA is responsible for the activation of the compounds, and by mass spectrometry we identified the active metabolite of 7947882, which directly inhibits PyrG activity. Metabolomic studies revealed that pharmacological inhibition of PyrG strongly perturbs DNA and RNA biosynthesis, and other metabolic processes requiring nucleotides. Finally, the crystal structure of PyrG was solved, paving the way for rational drug design with this newly validated drug target.

The fatty acid oxidation product 15-A3t-Isoprostane is a potent inhibitor of NFκB transcription and macrophage transformation

J. Neurochem. (2011) 119, 604–616.

Improved Synthesis of (E)-12-Nitrooctadec-12-enoic acid, a Potent PPARγ Activator. Development of a “Buffer-Free” Enzymatic Method for Hydrolysis of Methyl Esters

Endogenous nitro-fatty acids, acting as partial agonist of PPARγ, are able to lower the insulin and glucose levels without the side effects associated with common antidiabetic drugs. (E)-12-Nitrooctadec-12-enoic acid, a potent activator of this peroxisome receptor, was synthesized in a very efficient sequence via a Henry-retro-Claisen ring fragmentation, followed by a novel enzymatic cleavage of methyl esters. The latter method was then applied in the last step of the synthesis of a few labile natural products, such as prostaglandins, isoprostanes, and phytoprostanes.

One‐Pot Consecutive Reactions Based on the Synthesis of Conjugated Enones by the Re‐Catalysed Meyer–Schuster Rearrangement

Re catalysis in one-pot reactions: An atom-economical, one-pot strategy that involves alkyne deprotonation and a subsequent rhenium(V)-catalysed Meyer-Schuster rearrangement of the alkynol to provide α,ß-unsaturated enones in high yield has been developed (see scheme). Subsequent in situ hydride reduction or Diels-Alder reaction of the enones provided products in good-to-high overall yields.

Enantioselective Synthesis and Olfactory Evaluation of 13‐Alkyl‐Substituted α‐Ionones

To study the influence of the steric bulk of the substituents at C(5) on the olfactory characteristics of α‐ionone, the (S)‐antipodes of compounds 8–10 were synthesized starting from (S)‐α‐cyclogeraniol (14a). The latter was available in useful preparative yield with 95% ee by enantioselective lipase‐PS‐mediated acetylation of the racemic mixture. Key step in the conversion of 14a to 8–10 was an SN2′‐type reaction of an organocuprate on the allylic phosphate 20, which appears to be a general method for the introduction of an alkyl substituent at the cyclohexene CC bond of ionones. Olfactory evaluation showed that, compared to the parent (S)‐α‐ionone (1), the odor strength and fragrance facets of the three analogues 8–10 are significantly influenced by the bulkiness of the substituent at C(13), giving further evidence that hydrophobic interactions of this group play a significant role in the chemoreception of ionones. In particular, the odor of the ethyl derivative 8 was found to be significantly stronger than that of the parent (S)‐α‐ionone (1).

Fast low-pressurized microwave-assisted extraction of benzotriazole, benzothiazole and benezenesulfonamide compounds from soil samples

Benzotriazoles (BTRs), benzothiazoles (BTs) and benzenesulfonamides (BSAs), compounds largely used in industrial and household applications, are ubiquitous emerging contaminants. In this work a novel, straightforward procedure for the simultaneous determination of two BTRs (1H-benzotriazole, 5-methyl-1H-benzotriazole), three BTs (benzothiazole, 2-hydroxybenzothiazole, 2-methylthiobenzothiazole) and two BSAs (benzenesulfonamide, toluenesulfonamide) in soil has been developed. The target analytes were extracted from soil by a single low-pressurized microwave-assisted extraction (MAE) cycle (120°C, 10min) and quantified by high-performance liquid chromatography with UV detection. For all the seven analytes, quantitative extraction yields (72-119%, n=4) were observed from recovery tests on soil samples (1g) spiked with 5, 10 and 50mg kg(-1), using 4mL water-methanol (85:15) as extracting solution. For the lower concentrations levels (100, 250 and 500μg kg(-1)), the analytes were extracted from soil samples (2-3g) using 6mL methanol, and the extract was pre-concentrated by evaporation before analysis; recoveries in the range 70-117% were obtained (n=4). Suitable intra-day and inter-day precision were observed, with values of relative standard deviation generally below 6% and 11% (n=4), respectively. Linearity was evaluated in the concentration range 0.5-10mg L(-1) by matrix-matched standards, obtaining r(2)>0.9996. The experimental method quantification limit (MQL) was 100μg kg(-1). The entire procedure has been successfully applied to the analysis of real impacted soil samples.

Stereodivergent strategy for neurofuran synthesis via palladium-catalyzed asymmetric allylic cyclization: total synthesis of 7-epi-ST-Δ(8)-10-neurofuran.

Neurofurans are formed in vivo in the human brain as a consequence of an increased oxidative stress, and they could be valuable biomarkers of the neuronal oxidative stress. In this paper, an enantioselective stereodivergent approach to two key neurofuran precursors, belonging to the AC and ST classes, has been developed starting from a single achiral precursor, the meso-diol 11. The absolute configuration of the THF cores was secured by a Pd-catalyzed asymmetric allylic alkylation using (S,S)-L1 and (R,R)-L2 ligands, respectively.