Design, synthesis and structure-activity-relationship of 1,5-tetrahydronaphthyridines as CETP inhibitors

Organocalcium Hydride-Catalyzed Intramolecular C(sp3)-H Annulation of Functionalized 2,6-Lutidines

This work reports an intramolecular C(sp³)-H annulation of functionalized 2,6-lutidines catalyzed by an organocalcium hydride [{(^DIPPnacnac)CaH(thf)}₂] (^DIPPnacnac = CH{(CMe)(2,6-ⁱPr₂-C₆H₃N)}₂). This reaction constitutes a streamlined approach for producing a new family of tetrahydro-1,5-naphthyridines and hexahydropyrido[3,2-b]azocines derivatives in good to excellent yields with high atom efficiency and broad substrates scope. A calcium alkyl complex was isolated from the stoichiometric reaction between calcium hydride and the substrate through deprotonation, which was structurally characterized and confirmed as the catalytic intermediate.

Aromaticity indices, electronic structural properties, and fuzzy atomic space investigations of naphthalene and its aza-derivatives

The aromaticity and CDFT properties of naphthalene and its aza-derivatives were theoretically investigated using density functional theory (DFT) electronic structure method. The reactivity and chemistry of Azanaphthalene (1-AN), 1, 2-diazanaphthalene (1, 2-DAN), 1, 3-diazanaphthalene (1, 3-DAN), 1, 4-diazanaphthalene (1,4-DAN), 1, 5-diazanaphthalene (1, 5-DAN), 1, 6-diazanaphthalene (1, 6-DAN), 1, 7-diazanaphthalene (1,7-DAN) and 1, 8-diazanaphthalene (1, 8-DAN) were thoroughly explored and predicted focusing more on the fuzzy atomic space analysis, quantum chemical descriptors (CDFT), natural bond orbital (NBO), and structural electronic properties. The CDFT is focused on predicting the condensed Fukui function and dual descriptors along with condensed local electrophilicity and nucleophilicity investigation. From the aromaticity computational study, 1,7-DAN gave PDI, FLU, FLU- π , PLR, HOMA, BIRD and LOLIPOP values of approximately one (1) was found to be the most aromatic in the group, and strongest π -stacking ability. The aromaticity follows the trend: 1, 7-DAN > 1, 8-DAN > 1, 5-DAN > 1, 6-DAN > 1, 4-DAN > 1, 2-DAN > 1-AN > naphthalene. The second order perturbation energy NBO analysis revealed that the 3 highest stabilization energies in the molecules are C₆-N_a to C₃-C₄ ( π ∗ - π ∗ 236.90 kcal/mol) of 1, 6-DAN, C₃-C₄ to C₁-C₂ ( π ∗ - π ∗ 236.37 kcal/mol) of 1-AN and C₇-N₁₀ to C₂-C₄ ( π ∗ - π ∗ 235 kcal/mol) of 1, 3-DAN.

Ruthenium/acid co-catalyzed reductive α-phosphinoylation of 1,8-naphthyridines with diarylphosphine oxides

By an in situ coupling-interrupted transfer hydrogenation strategy, a direct construction of novel α-phosphinoyl 1,2,3,4-tetrahydronaphthyridines via ruthenium/acid co-catalyzed reductive α-phosphinoylation of 1,8-naphthyridines with diarylphosphine oxides is demonstrated.

Synthetic Strategies, Reactivity and Applications of 1,5-Naphthyridines

This review covers the synthesis and reactivity of 1,5-naphthyridine derivatives published in the last 18 years. These heterocycles present a significant importance in the field of medicinal chemistry because many of them exhibit a great variety of biological activities. First, the published strategies related to the synthesis of 1,5-naphthyridines are presented followed by the reactivity of these compounds with electrophilic or nucleophilic reagents, in oxidations, reductions, cross-coupling reactions, modification of side chains or formation of metal complexes. Finally, some properties and applications of these heterocycles studied during this period are examined.

Transition metal-free α-methylation of 1,8-naphthyridine derivatives using DMSO as methylation reagent

A practical approach to the direct α-methylation of 1,8-naphthyridines under mild reaction conditions has been developed using simple and readily available DMSO as a convenient and environmentally friendly carbon source. This method is transition metal-free and highly chemoselective, shows good functional group tolerance, and uses DMSO as a methyl source, providing efficient and rapid access to an important compound class, 2-methyl-1,8-naphthyridines.

Potential Inhibitors of the Activity of the Cholesterol-Ester Transfer Protein

The cholesterol-ester transfer protein (CETP) exchanges lipids between high-density lipoproteins (HDLs) and low-density lipoproteins (LDLs). The excessive transport of lipids from HDLs to LDLs mediated by this protein can cause an alteration in the deposition of lipoproteins onto the arterial walls, thus promoting the development of arteriosclerosis. Different CETP inhibitors have been tested in recent years, but none has been confirmed as being effectively palliative for the disease. We employed in silico databases and molecular docking as a computational method to predict how potential CETP inhibitors could interact with the active site of the CETP protein. Upon previously comparing two computer software packages to determine which generated a greater number of accurate CETP-inhibitor-complex structures, we chose the more appropriate program for our studies. We then abstracted a series of databases of known CETP inhibitors and noninhibitors exhibiting different 50% concentrations of CETP-inhibitory (INH) activity, to generate virtual structures for docking with different combinations of the CETP receptor. From this process, we obtained as the most suitable structure 4F2A_1OB_C_PCW-it accordingly having a greater area under the receiver operating characteristic curve. The molecular docking of known compounds in comparison with the respective conformation of this inhibitor enabled us to obtain ΔGs (in kcal/mol) from which data we made a first exploration of unknown compounds for CETP-INH activity. Thus, the 4F2A_1OB_C_PCW structure was docked with DrugBank-Approved commercial compounds in an extensive database, whose status had already been established from pharmacokinetics and toxicology. In this study, we present a group of potential compounds as CETP-inhibitor candidates.

Transfer hydrogenative para-selective aminoalkylation of aniline derivatives with N-heteroarenes via ruthenium/acid dual catalysis

By ruthenium/acid dual catalysis, a novel transfer hydrogenative para-selective aminoalkylation of aniline derivatives with N-heteroarenes has been demonstrated.

Hydrogen-Transfer-Mediated α-Functionalization of 1,8-Naphthyridines by a Strategy Overcoming the Over-Hydrogenation Barrier

A general catalytic hydrogen transfer-mediated α-functionalization of 1,8-naphthyridines is reported for the first time that benefits from a hydrogen transfer-mediated activation mode for non-activated pyridyl cores. The pyridyl α-site selectively couples with the C8-site of various tetrahydroquinolines (THQs) to afford novel α-functionalized tetrahydro 1,8-naphthyridines, a class of synthetically useful building blocks and potential candidates for the discovery of therapeutic and bio-active products. The utilization of THQs as inactive hydrogen donors (HDs) appears to be a key strategy to overcome the over-hydrogenation barrier and address the chemoselectivity issue. The developed chemistry features operational simplicity, readily available catalyst and good functional group tolerance, and offers a significant basis for further development of new protocols to directly transform or functionalize inert N-heterocycles.

The Synthesis of 5-Amino-dihydrobenzo[b]oxepines and 5-Amino-dihydrobenzo[b]azepines via Ichikawa Rearrangement and Ring-Closing Metathesis

The combination of Ichikawa's rearrangement and a ring-closing metathesis reaction of allyl carbamates is presented as a method for the preparation of 5-amino-substituted 2,5-dihydro-benzo[b]oxepines, 2,5-dihydro-benzo[b]azepines, and 2,5-dihydro-benzo[b]thiepins. It was demonstrated that the use of nonracemic allyl carbamates enables the synthesis of enantioenriched benzo-fused seven-membered heterocycles. Finally, it was shown that further functionalization of the obtained structures allows access to pharmacologically active 5-amino-substituted 2,3,4,5-tetrahydro-1-benzo[b]oxepine scaffolds.

Molecular inflation, attrition and the rule of five

Physicochemical properties underlie all aspects of drug action and are critical for solubility, permeability and successful formulation. Specific physicochemical properties shown to be relevant to oral drugs are size, lipophilicity, ionisation, hydrogen bonding, polarity, aromaticity and shape. The rule of 5 (Ro5) and subsequent studies have raised awareness of the importance of compound quality amongst bioactive molecules. Lipophilicity, probably the most important physical property of oral drugs, has on average changed little over time in oral drugs, until increases in drugs published after 1990. In contrast other molecular properties such as average size have increased significantly. Factors influencing property inflation include the targets pursued, where antivirals frequently violate the Ro5, risk/benefit considerations, and variable drug discovery practices. The compounds published in patents from the pharmaceutical industry are on average larger, more lipophilic and less complex than marketed oral drugs. The variation between individual companies' patented compounds is due to different practices and not to the targets pursued. Overall, there is demonstrable physical property attrition in moving from patents to candidate drugs to marketed drugs. The pharmaceutical industry's recent poor productivity has been due, in part, to progression of molecules that are unable to unambiguously test clinical efficacy, and attrition can therefore be improved by ensuring candidate drug quality is 'fit for purpose.' The combined ligand efficiency (LE) and lipophilic ligand efficiency (LLE) values of many marketed drugs are optimised relative to other molecules acting at the same target. Application of LLE in optimisation can help identify improved leads, even with challenging targets that seem to require lipophilic ligands. Because of their targets, some projects may need to pursue 'beyond Ro5' physicochemical space; such projects will require non-standard lead generation and optimisation and should not dominate in a well-balanced portfolio. Compound quality is controllable by lead selection and optimisation and should not be a cause of clinical failure.

Asymmetric nucleophilic dearomatization of diazarenes by anion-binding catalysis

The first highly regio- and enantioselective nucleophilic dearomatization of diazarenes by anion-binding organocatalysis is reported.

New Diterpenes from Cultures of the Fungus Engleromyces goetzii and Their CETP Inhibitory Activity

One new cleistanthane-type diterpene named engleromycenolic acid A (1), one new rosane-type diterpene named engleromycenolic acid B (2) and one new natural rosane-type diterpene, engleromycenol (3), along with three known rosane-type diterpenes, rosololactone (4), rosenonolactone (5) and 7-deoxyrosenonolactone (6) were isolated from cultures of the fungus Engleromyces goetzii, where it naturally grows on Alpine bamboo culms. The new compounds were elucidated based on their spectroscopic data. In addition, compounds 1-6 were evaluated for their cholesterol ester transfer protein (CETP) inhibition activity. This paper reports the isolation, structural elucidation, and CETP inhibition activity of these compounds.

Future of cholesteryl ester transfer protein (CETP) inhibitors: a pharmacological perspective

In almost 30 years since the introduction of HMG-CoA reductase inhibitors (statins), no other class of lipid modulators has entered the market. Elevation of high-density lipoprotein-cholesterol (HDL-C) via inhibiting cholesteryl ester transfer protein (CETP) is an attractive strategy for reducing the risk of cardiovascular events in high-risk patients. Transfer of triglyceride and cholesteryl ester (CE) between lipoproteins is mediated by CETP; thus inhibition of this pathway can increase the concentration of HDL-C. Torcetrapib was the first CETP inhibitor evaluated in phase III clinical trials. Because of off-target effects, torcetrapib raised blood pressure and increased the concentration of serum aldosterone, leading to higher cardiovascular events and mortality. Torcetrapib showed positive effects on cardiovascular risk especially in patients with a greater increase in HDL-C and apolipoprotein A-1 (apoA-1) levels. The phase III clinical trial of dalcetrapib, the second CETP inhibitor that has entered clinical development, was terminated because of ineffectiveness. Dalcetrapib is a CETP modulator that elevated HDL-C levels but did not reduce the concentration of low-density lipoprotein cholesterol (LDL-C). Both heterotypic and homotypic CE transfer between lipoproteins are mediated by some CETP inhibitors, including torcetrapib, anacetrapib, and evacetrapib, while dalcetrapib only affects the heterotypic CE transfer. Dalcetrapib has a chemical structure that is distinct from other CETP inhibitors, with a smaller molecular weight and a lack of trifluoride moieties. Moreover, dalcetrapib is a pro-drug that must be hydrolyzed to a pharmacologically active thiol form. Two other CETP inhibitors, anacetrapib and evacetrapib, are currently undergoing evaluation in phase III clinical trials. Both molecules have shown beneficial effects by increasing HDL-C and decreasing LDL-C concentration. The success of anacetrapib and evacetrapib remains to be confirmed upon the completion of phase III clinical trials in 2017 and 2015, respectively. Generally, the concentration of HDL-C has been considered a biomarker for the activity of CETP inhibitors. However, it is not clear whether a fundamental relationship exists between HDL-C levels and the risk of coronary artery diseases. The most crucial role for HDL is cholesterol efflux capacity in which HDL can reverse transport cholesterol from foam cells in atherosclerotic plaques. In view of the heterogeneity in HDL particle size, charge, and composition, the mere concentration of HDL-C may not be a good surrogate marker for HDL functionality. Recent clinical studies have reported that increased HDL functionality inversely correlates with the development of atherosclerotic plaque. Future development of CETP inhibitors may therefore benefit from the use of biomarkers of HDL functionality.