II. Synthesis of Heteroarotinoid Scaffolds for Anticancer Agents

An efficient route to synthesize various heterocycles has been developed based on tandem reactions initiated by a dissolving metal reduction. New methods have been developed which involves either the use of a tandem reduction-reductive amination, reduction-cyclization or a reduction-lactamization sequence to achieve potentially valuable target molecules. The key steps involved in the procedure are (i) reduction of an aromatic nitro group using iron in presence of an acid followed by (ii) intramolecular cyclization with either an aldehyde, ketone, ester or alpha, Beta-unsaturated ketone. Different heterocycles such as carbazoles, pyridoindolones, spiro-fused 3,4-dihydro-2(1H)-quinolinone derivative, two tricyclic linear fused rings system, aryl and alkyl dihydro-4(1H)-quinazolinones, 4(1H)-quinolinones and dihydroquinolinones were successfully synthesized by this method. The use of these mild procedures allows reasonable structural variation and avoids the use of hazardous reagents or expensive catalysts. Some of the heterocyclic targets prepared by this method are currently used as drugs or are precursors to drugs in advanced clinical studies. A commercial route for the sythesis of SHetA2 heteroarotinoid ring was developed. Syntheses of metabolites of SHetA2 were developed using a 17-step synthetic route.Chemistry Departmen

Small Molecule Inhibitors of the BfrB-Bfd Interaction Decrease Pseudomonas aeruginosa Fitness and Potentiate Fluoroquinolone Activity

© 2019 American Chemical Society. All rights reserved. The iron storage protein bacterioferritin (BfrB) is central to bacterial iron homeostasis. The mobilization of iron from BfrB, which requires binding by a cognate ferredoxin (Bfd), is essential to the regulation of cytosolic iron levels in P. aeruginosa. This paper describes the structure-guided development of small molecule inhibitors of the BfrB-Bfd protein-protein interaction. The process was initiated by screening a fragment library and followed by obtaining the structure of a fragment hit bound to BfrB. The structural insights were used to develop a series of 4-(benzylamino)- A nd 4-((3-phenylpropyl)amino)-isoindoline-1,3-dione analogs that selectively bind BfrB at the Bfd binding site. Challenging P. aeruginosa cells with the 4-substituted isoindoline analogs revealed a dose-dependent growth phenotype. Further investigation determined that the analogs elicit a pyoverdin hyperproduction phenotype that is consistent with blockade of the BfrB-Bfd interaction and ensuing irreversible accumulation of iron in BfrB, with concomitant depletion of iron in the cytosol. The irreversible accumulation of iron in BfrB prompted by the 4-substituted isoindoline analogs was confirmed by visualization of BfrB-iron in P. aeruginosa cell lysates separated on native PAGE gels and stained for iron with Ferene S. Challenging P. aeruginosa cultures with a combination of commercial fluoroquinolone and our isoindoline analogs results in significantly lower cell survival relative to treatment with either antibiotic or analog alone. Collectively, these findings furnish proof of concept for the usefulness of small molecule probes designed to dysregulate bacterial iron homeostasis by targeting a protein-protein interaction pivotal for iron storage in the bacterial cell

Recent Syntheses of 1,2,3,4-Tetrahydroquinolines, 2,3-Dihydro-4(1H)-quinolinones and 4(1H)-Quinolinones using Domino Reactions

A review of the recent literature is given focusing on synthetic approaches to 1,2,3,4-tetrahydroquinolines, 2,3-dihydro-4(1H)-quinolinones and 4(1H)-quinolinones using domino reactions. These syntheses involve: (1) reduction or oxidation followed by cyclization; (2) SNAr-terminated sequences; (3) acid-catalyzed ring closures or rearrangements; (4) high temperature cyclizations and (5) metal-promoted processes as well as several less thoroughly studied reactions. Each domino method is presented with a brief discussion of mechanism, scope, yields, simplicity and potential utility

OSU-6: A Highly Efficient, Metal-Free, Heterogeneous Catalyst for the Click Synthesis of 5-Benzyl and 5-Aryl-1H-tetrazoles

OSU-6, an MCM-41 type hexagonal mesoporous silica with mild Brönsted acid properties, has been used as an efficient, metal-free, heterogeneous catalyst for the click synthesis of 5-benzyl and 5-aryl-1H-tetrazoles from nitriles in DMF at 90 °C. This catalyst offers advantages including ease of operation, milder conditions, high yields, and reusability. Studies are presented that demonstrate the robust nature of the catalyst under the optimized reaction conditions. OSU-6 promotes the 1,3-dipolar addition of azides to nitriles without significant degradation or clogging of the nanoporous structure. The catalyst can be reused up to five times without a significant reduction in yield, and it does not require treatment with acid between reactions

Evaluation of New Dihydrophthalazine-Appended 2,4-Diaminopyrimidines against Bacillus anthracis: Improved Syntheses Using a New Pincer Complex

The synthesis and evaluation of ten new dihydrophthalazine-appended 2,4-diaminopyrimidines as potential drugs to treat Bacillus anthracis is reported. An improved synthesis utilizing a new pincer catalyst, dichlorobis[1-(dicyclohexylphosphanyl)-piperidine]palladium(II), allows the final Heck coupling to be performed at 90 °C using triethylamine as the base. These milder conditions have been used to achieve improved yields for new and previously reported substrates with functional groups that degrade or react at the normal 140 °C reaction temperature. An analytical protocol for separating the S and R enantiomers of two of the most active compounds is also disclosed. Finally, the X-ray structure for the most active enantiomer of the lead compound, (S)-RAB1, is given

Synthesis and Biological Evaluation of 2,4-Diaminopyrimidine-Based Antifolate Drugs against Bacillus anthracis

Due to the innate ability of bacteria to develop resistance to available antibiotics, there is a critical need to develop new agents to treat more resilient strains. As a continuation of our research in this area, we have synthesized a series of racemic 2,4-diaminopyrimidine-based drug candidates, and evaluated them against Bacillus anthracis. The structures are comprised of a 2,4-diaminopyrimidine ring, a 3,4-dimethoxybenzyl ring, and an N-acryloyl-substituted 1,2-dihydrophthalazine ring. Various changes were made at the C1 stereocenter of the dihydrophthalazine moiety in the structure, and the biological activity was assessed by measurement of the MIC and Ki values to identify the most potent drug candidate