Synthesis and SAR of novel histamine H3 receptor antagonists

Core-Shell Nano-Cobalt Catalyzed Chemoselective Reduction of N-Heteroarenes with Ammonia Borane

An easily prepared core-shell heterogeneous nanocobalt catalyst was reported, which could achieve selective reduction of N-heteroarenes with ammonia borane under mild conditions and ambient atmosphere. Various quinoline, quinoxaline, naphthyridine, isoquinoline, acridine, and phenanthroline derivatives were hydrogenated with high selectivity and efficiency. Notably, substrates bearing sensitive functional groups under molecular hydrogen reduction conditions, such as cyano, ester, and halogens were well tolerated by the catalytic system. Moreover, with our novel method several bioactive molecules were prepared. Also, this catalyst could be applied in the liquid organic hydrogen storage system by reversible hydrogenation and dehydrogenation of heteroarene in high efficiencies.

A robust iron catalyst for the selective hydrogenation of substituted (iso)quinolones

By applying N-doped carbon modified iron-based catalysts, the controlled hydrogenation of N-heteroarenes, especially (iso)quinolones, is achieved. Crucial for activity is the catalyst preparation by pyrolysis of a carbon-impregnated composite, obtained from iron(ii) acetate and N-aryliminopyridines. As demonstrated by TEM, XRD, XPS and Raman spectroscopy, the synthesized material is composed of Fe(0), Fe3C and FeN x in a N-doped carbon matrix. The decent catalytic activity of this robust and easily recyclable Fe-material allowed for the selective hydrogenation of various (iso)quinoline derivatives, even in the presence of reducible functional groups, such as nitriles, halogens, esters and amides. For a proof-of-concept, this nanostructured catalyst was implemented in the multistep synthesis of natural products and pharmaceutical lead compounds as well as modification of photoluminescent materials. As such this methodology constitutes the first heterogeneous iron-catalyzed hydrogenation of substituted (iso)quinolones with synthetic importance.

Evaluation of Antibacterial Activity and Reactive Species Generation of N-Benzenesulfonyl Derivatives of Heterocycles

Two N-benzenesulfonyl (BS) derivatives of 1,2,3,4-tetrahydroquinoline (THQ) were designed, prepared, and screened for antibacterial activity. This approach was based on combining the two privileged structures, BS and THQ, which are known to be active. The objective of this study was to evaluate the antibacterial activity of BS-THQ and its analogue 4-NH2BS-THQ, and to investigate the roles of reactive oxygen species and reactive nitrogen species in their lethality. Both showed bactericidal activity against Staphylococcus aureus ATCC 29213 and methicillin-resistant S. aureus (MRSA) ATCC 43300, with transmission electron microscopy revealing a disturbed membrane architecture. Furthermore, an increase of reactive oxygen species (ROS) in strains treated with BS-THQ with respect to the control was detected when fluorescent microscopy and spectrophotometric techniques were used. The analogue 4-NH2BS-THQ demonstrated a broader spectrum of activity than BS-THQ, with a minimum inhibitory concentration of 100 µg/mL against reference strains of S. aureus, Escherichia coli and Pseudomonas aeruginosa. The assayed compounds represent promising structures for the development of new synthetic classes of antimicrobials.

TD-DFT calculations of UV absorption bands and their intensities in the spectra of some tetrahydroquinolines

A detailed analysis of the MOs involved in the electronic transitions of 1-benzenesulfonyl-1,2,3,4-tetrahydroquinolines is presented for the first time.

Dual histamine H3R/serotonin 5-HT4R ligands with antiamnesic properties: pharmacophore-based virtual screening and polypharmacology

In recent years, preclinical and clinical studies have generated considerable interest in the development of histamine H3 receptor (H3R) antagonists as novel treatment for degenerative disorders associated with impaired cholinergic function. To identify novel scaffolds for H3R antagonism, a common feature-based pharmacophore model was developed and used to screen the 17,194 compounds of the CERMN (Centre d'Etudes et de Recherche sur le Médicament de Normandie) chemical library. Out of 268 virtual hits which have been gathered in 34 clusters, we were particularly interested in tricyclic derivatives also exhibiting a potent 5HT4R affinity. Benzo[h][1,6]naphthyridine derivatives showed the highest H3R affinity, and compound 17 (H3R Ki = 41.6 nM; 5-HT4R Ki = 208 nM) completely reversed the amnesiant effect of scopolamine at 3 mg/kg in a spatial working memory experiment. For the first time we demonstrated the feasibility to combine H3R and 5-HT4R activities in a single molecule, raising the exciting possibility that dual H3R antagonist/5HT4R agonist have potential for the treatment of neurodegenerative diseases such as Alzheimer's disease.

Development of 3,4-dihydroisoquinolin-1(2H)-one derivatives for the Positron Emission Tomography (PET) imaging of σ₂ receptors

σ₂ Receptors are promising biomarkers for cancer diagnosis given the relationship between the proliferative status of tumors and their density. With the aim of contributing to the research of σ₂ receptor Positron Emission Tomography (PET) probes, we developed 2-[3-[6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl]propyl]-3,4-dihydroisoquinolin-1(2H)-one (3), with optimal σ₂ pharmacological properties and appropriate lipophilicity. Hence, 3 served as the lead compound for the development of a series of dihydroisoquinolinones amenable to radiolabeling. Radiosynthesis for compound 26, which displayed the most appropriate σ₂ profile, was developed and σ₂ specific binding for the corresponding [(18)F]-26 was confirmed by in vitro autoradiography on rat brain slices. Despite the excellent in vitro properties, [(18)F]-26 could not successfully image σ₂ receptors in the rat brain in vivo, maybe because of its interaction with P-gp. Nevertheless, [(18)F]-26 may still be worthy of further investigation for the imaging of σ₂ receptors in peripheral tumors devoid of P-gp overexpression.

Rhodium-catalyzed hydroformylation in fused azapolycycles synthesis

N-Heterocycles, including fused ones, have proven to be an important class of compounds since they possess biological and pharmacological activities themselves and serve as valuable intermediates for synthetic drug discovery. My interest in the synthesis of these compounds stems from studies dealing with the hydroformylation (oxo) of olefins. The dihydroindolizines and benzofused ones are easily generated via rhodium-catalyzed hydroformylation of N-allylpyrroles and indoles: the butanal intermediate undergoes an intramolecular cyclodehydration giving the final polycyclic compound. This chapter reports my results in the area of the conversions of oxo aldehydes with additional C,C-bond-forming reactions together with relevant work from other laboratories on additional C,N-bond-forming reactions, encountered in the field of Azapolycycles synthesis over the last 5 years or so. The intramolecular sequences for polycylization will be especially emphasized using rhodium complexes to effect these transformations, under both conventional and microwave heating.

Synthesis of a unique isoindoline/tetrahydroisoquinoline-based tricyclic sultam library utilizing a Heck-aza-Michael strategy

The synthesis of a unique isoindoline- and tetrahydroisoquinoline (THIQ)-containing tricyclic sultam library, utilizing a Heck-aza-Michael (HaM) strategy is reported. Both isoindoline and THIQ rings are installed through a Heck reaction on a vinylsulfonamide, followed by one-pot deprotection and intramolecular aza-Michael reaction. Subsequent cyclization with either paraformaldehyde condensation or 1,1'-carbonyldiimidazole coupling generates a variety of tricyclic sultams. Overall, a 160-member library of these sultams, together with their isoindolines/THIQ and secondary sulfonamides precursors, were constructed using this strategy.

A novel class of H3 antagonists derived from the natural product guided synthesis of unnatural analogs of the marine bromopyrrole alkaloid dispyrin

This Letter describes the natural product guided synthesis of unnatural analogs of the marine bromopyrrole alkaloid dispyrin, and the resulting SAR of H(3) antagonism. Multiple rounds of iterative parallel synthesis improved human H(3) IC(50) approximately 33-fold, and afforded a new class of H(3) antagonists based on the novel bromotyramine core of dispyrin.

Histamine H3 receptor ligands break ground in a remarkable plethora of therapeutic areas

The neurotransmitter histamine exerts its action through four distinct histamine receptors. The histamine H(1) and H(2) receptor are well established drug targets, whereas the histamine H(4) receptor is undergoing rigorous characterisation at present. The histamine H(3) receptor (H(3)R) is a G(i/o)-protein coupled receptor and is mostly expressed in the CNS. A remarkably large and different array of therapeutic areas, in which ligands for the H(3)R may prove useful, has been identified and a massive research undertaking is underway to substantiate the high expectations for H(3)R ligands. At present, several ligands for the H(3)R are being evaluated in clinical studies. In this review, the many potential therapeutic areas for H(3)R antagonists, inverse agonists and agonists is discussed. Promising medicinal chemistry and toxicological developments, as well as the advancement of several H(3)R ligands into the clinic, will be highlighted. This review also describes the problems that have been overcome and the questions that remain in developing H(3)R-related drugs. Considering the tremendous efforts by industry, it can be expected that the first H(3)R drugs will reach the market soon.

Cyclopentanone Ring Expansion Leading to Functionalized δ-Lactams: Short Synthesis of Simple Sedum Alkaloids

Monosubstituted epoxides react with (cyclopentenyloxy)trimethylsilane to afford, after subsequent oxidative fragmentation, a pair of diastereomeric 8-membered iodolactones. When these lactones are separately treated with sodium azide, followed by reduction over Lindlar's catalyst, lactone ring contraction yields 6-membered monosubstituted lactams. When (R)-1,2-epoxypentane is used in this 5 + 3 - 2 overall ring expansion sequence, one final step involving delta-lactam to piperidine reduction yields natural (-)-halosaline and (-)-epihalosaline in five steps and 12% and 23% overall yields, respectively.

Dual serotonin transporter/histamine H3 ligands: Optimization of the H3 pharmacophore

A series of tetrahydroisoquinolines acting as dual histamine H3/serotonin transporter ligands is described. A highly regio-selective synthesis of the tetrahydroisoquinoline core involving acid mediated ring-closure of an acetophenone intermediate followed by reduction with NaCNBH3 was developed. In vitro and in vivo data are discussed.

Rhodium(i)-catalyzed hydroaminomethylation of 2-isopropenylanilines as a novel route to 1,2,3,4-tetrahydroquinolines

A new atom economical approach for the preparation of 1,2,3,4-tetrahydroquinolines can be achieved by means of the intramolecular hydroaminomethylation of 2-isopropenylanilines, mediated by an ionic diamino rhodium catalyst that does not require phosphine--this reaction is highly chemo- and regioselective, and it occurs in good isolated yields.