Optimization and Mechanistic Investigations of Novel Allosteric Activators of PKG1α.

Activation of PKG1α is a compelling strategy for the treatment of cardiovascular diseases. As the main effector of cyclic guanosine monophosphate (cGMP), activation of PKG1α induces smooth muscle relaxation in blood vessels, lowers pulmonary blood pressure, prevents platelet aggregation, and protects against cardiac stress. The development of activators has been mostly limited to cGMP mimetics and synthetic peptides. Described herein is the optimization of a piperidine series of small molecules to yield activators that demonstrate in vitro phosphorylation of vasodilator-stimulated phosphoprotein as well as antiproliferative effects in human pulmonary arterial smooth muscle cells. Hydrogen/deuterium exchange mass spectrometry experiments with the small molecule activators revealed a mechanism of action consistent with cGMP-induced activation, and an X-ray co-crystal structure with a construct encompassing the regulatory domains illustrated a binding mode in an allosteric pocket proximal to the low-affinity cyclic nucleotide-binding domain.

Invention of MK-8262, a Cholesteryl Ester Transfer Protein (CETP) Inhibitor Backup to Anacetrapib with Best-in-Class Properties.

Cholesteryl ester transfer protein (CETP) represents one of the key regulators of the homeostasis of lipid particles, including high-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles. Epidemiological evidence correlates increased HDL and decreased LDL to coronary heart disease (CHD) risk reduction. This relationship is consistent with a clinical outcomes trial of a CETP inhibitor (anacetrapib) combined with standard of care (statin), which led to a 9% additional risk reduction compared to standard of care alone. We discuss here the discovery of MK-8262, a CETP inhibitor with the potential for being the best-in-class molecule. Novel in vitro and in vivo paradigms were integrated to drug discovery to guide optimization informed by a critical understanding of key clinical adverse effect profiles. We present preclinical and clinical evidence of MK-8262 safety and efficacy by means of HDL increase and LDL reduction as biomarkers for reduced CHD risk.

Mild Condition for the Deoxygenation of α-Heteroaryl-Substituted Methanol Derivatives.

A mild condition via PPh3/I2/imidazole for the deoxygenation of substituted methanol derivatives has been identified. This metal-free process was found to proceed well on secondary or tertiary alcohols substituted with one or two heteroaryl groups, and it tolerates acid-sensitive heterocycles. This condition works for methanol derivatives substituted with 2-pyridyl, 4-pyridyl, or other heterocyclic groups, allowing the negative charge formed during the reaction to resonate to a nitrogen atom. Methanol derivatives substituted with 3-pyridyl or heterocyclic groups that do not allow the negative charge formed during the reaction to resonate to a nitrogen atom will not undergo deoxygenation under this condition.

Scalable Preparation of 4,4-Disubstituted Six-Membered Cyclic Sulfones.

We provide an account of synthetic strategies aimed at the efficient preparation of 4-amino-4-methyltetrahydro-2H-thiopyran 1,1-dioxide (3), an important cyclic sulfone building block for medicinal chemistry. A practical and scalable protocol has been developed that readily gives access to the title compound from commercially available and inexpensive starting materials. In addition, this novel approach has enabled the synthesis of various related 4,4-disubstituted cyclic sulfone derivatives that serve as valuable structural motifs for drug discovery.

A General One-Pot Protocol for Hindered N-Alkyl Azaheterocycles from Tertiary Carboxylic Acids.

In this letter, we report a general one-pot strategy that utilizes three elementary steps (decarboxylative hydrazination, Boc deprotection, and heterocycle condensation) to regioselectively prepare hindered C(sp3) substituted pyrazoles and triazoles. The operational simplicity of this sequence and ubiquity of tertiary carboxylic acids allow rapid access to hindered N-alkyl azaheterocycles that will be useful to practitioners of medicinal chemistry and agro-chemistry.

Selective N7 Alkylation of 7-Azaindazoles.

A general and mild procedure for alkylation of 7-azaindazoles at the N7 position using alkyl halides in butanone is reported, which requires no additives such as acids or bases. The scope of the reaction regarding substituents on 7-azaindazoles and the alkyl electrophiles is presented.

Discovery of [11C]MK-6884: A Positron Emission Tomography (PET) Imaging Agent for the Study of M4Muscarinic Receptor Positive Allosteric Modulators (PAMs) in Neurodegenerative Diseases.

The measurement of receptor occupancy (RO) using positron emission tomography (PET) has been instrumental in guiding discovery and development of CNS directed therapeutics. We and others have investigated muscarinic acetylcholine receptor 4 (M4) positive allosteric modulators (PAMs) for the treatment of symptoms associated with neuropsychiatric disorders. In this article, we describe the synthesis, in vitro, and in vivo characterization of a series of central pyridine-related M4 PAMs that can be conveniently radiolabeled with carbon-11 as PET tracers for the in vivo imaging of an allosteric binding site of the M4 receptor. We first demonstrated its feasibility by mapping the receptor distribution in mouse brain and confirming that a lead molecule 1 binds selectively to the receptor only in the presence of the orthosteric agonist carbachol. Through a competitive binding affinity assay and a number of physiochemical properties filters, several related compounds were identified as candidates for in vivo evaluation. These candidates were then radiolabeled with 11C and studied in vivo in rhesus monkeys. This research eventually led to the discovery of the clinical radiotracer candidate [11C]MK-6884.

A diversity-oriented rhodamine library for wide-spectrum bactericidal agents with low inducible resistance against resistant pathogens.

Antimicrobial resistance is a public health emergency and warrants coordinated global efforts. Challenge is that no alternative molecular platform has been identified for discovery of abundant antimicrobial hit compounds. Xanthene libraries have been screened for bioactive compounds. However, the potentially accessible chemistry space of xanthene dyes is limited by the existing xanthene synthesis. Herein we report a mild one-step synthesis, which permits late-stage introduction of a xanthene moiety onto i.e. natural products, pharmaceuticals, and bioactive compounds and construction of a focused library of rhodamine dyes exhibiting facile functional, topographical and stereochemical diversity. In vitro screening yields 37 analogs with mid-to-high bactericidal activity against WHO priority drug-resistant pathogens. These findings suggest that synthetic dye libraries exhibiting high structural diversity is a feasible chemical space combating antibacterial resistance, to complement the natural sources.

Optimization of Preclinical Metabolism for Somatostatin Receptor Subtype 5-Selective Antagonists.

A series of structurally diverse azaspirodecanone and spirooxazolidinone analogues were designed and synthesized as potent and selective somatostatin receptor subtype 5 (SSTR5) antagonists. Four optimized compounds each representing a subseries showed improvement in their metabolic stability and pharmacokinetic profiles compared to those of the original lead compound 1 while maintaining pharmacodynamic efficacy. The optimized cyclopropyl analogue 13 demonstrated efficacy in a mouse oral glucose tolerance test and an improved metabolic profile and pharmacokinetic properties in rhesus monkey studies. In this Communication, we discuss the relationship among structure, in vitro and in vivo activity, metabolic stability, and ultimately the potential of these compounds as therapeutic agents for the treatment of type 2 diabetes. Furthermore, we show how the use of focused libraries significantly expanded the structural class and provided new directions for structure-activity relationship optimization.

A Water-Soluble, Green-Light Triggered, and Photo-Calibrated Nitric Oxide Donor for Biological Applications.

Nitric oxide (NO) is a versatile endogenous molecule, involved in various physiological processes and implicated in the progression of many pathological conditions. Therefore, NO donors are valuable tools in NO related basic and applied applications. The traditional spontaneous NO donors are limited in scenarios where flux, localization, and dose of NO could be monitored. This has promoted the development of novel NO donors, whose NO release is not only under control, but also self-calibrated. Herein, we reported a phototriggered and photocalibrated NO donor (NOD565) with an N-nitroso group on a rhodamine dye. NOD565 is nonfluorescent and could release NO efficiently upon irradiation by green light. A bright rhodamine dye is generated as a side-product and its fluorescence can be used to monitor the NO release. The potentials of NOD565 in practical applications are showcased in in vitro studies, e.g., platelet aggregation inhibition and fungi growth suppression.

Composition-dependent electrocatalytic activity of palladium-iridium binary alloy nanoparticles supported on the multiwalled carbon nanotubes for the electro-oxidation of formic acid.

Surface-functionalized multiwalled carbon nanotubes (MWCNTs) supported Pd100-xIrx binary alloy nanoparticles (Pd100-xIrx/MWCNT) with tunable Pd/Ir atomic ratios were synthesized by a thermolytic process at varied ratios of bis(acetylacetonate) palladium(II) and iridium(III) 2,4-pentanedionate precursors and then applied as the electrocatalyst for the formic acid electro-oxidation. The X-ray diffraction pattern (XRD) and transmission electron microscope (TEM) analysis showed that the Pd100-xIrx alloy nanoparticles with the average size of 6.2 nm were uniformly dispersed on the MWCNTs and exhibited a single solid solution phase with a face-centered cubic structure. The electrocatalytic properties were evaluated through the cyclic voltammetry and chronoamperometry tests, and the results indicated that both the activity and stability of Pd100-xIrx/MWCNT were strongly dependent on the Pd/Ir atomic ratios: the best electrocatalytic performance in terms of onset potential, current density, and stability against CO poisoning was obtained for the Pd79Ir21/MWCNT. Moreover, compared with pure Pd nanoparticles supported on MWCNTs (Pd/MWCNT), the Pd79Ir21/MWCNT exhibited enhanced steady-state current density and higher stability, as well as maintained excellent electrocatalytic activity in high concentrated formic acid solution, which was attributed to the bifunctional effect through alloying Pd with transition metal.

2-[(3aR,4R,5S,7aS)-5-{(1S)-1-[3,5-bis(trifluoromethyl)phenyl]-2-hydroxyethoxy}-4-(2-methylphenyl)octahydro-2H-isoindol-2-yl]-1,3-oxazol-4(5H)-one: a potent human NK1 receptor antagonist with multiple clearance pathways.

Hydroisoindoline 2 has been previously identified as a potent, brain-penetrant NK1 receptor antagonist with a long duration of action and improved profile of CYP3A4 inhibition and induction compared to aprepitant. However, compound 2 is predicted, based on data in preclinical species, to have a human half-life longer than 40 h and likely to have drug-drug-interactions (DDI), as 2 is a victim of CYP3A4 inhibition caused by its exclusive clearance pathway via CYP3A4 oxidation in humans. We now report 2-[(3aR,4R,5S,7aS)-5-{(1S)-1-[3,5-bis(trifluoromethyl)phenyl]-2-hydroxyethoxy}-4-(2-methylphenyl)octahydro-2H-isoindol-2-yl]-1,3-oxazol-4(5H)-one (3) as a next generation NK1 antagonist that possesses an additional clearance pathway through glucuronidation in addition to that via CYP3A4 oxidation. Compound 3 has a much lower propensity for drug-drug interactions and a reduced estimated human half-life consistent with once daily dosing. In preclinical species, compound 3 has demonstrated potency, brain penetration, and a safety profile similar to 2, as well as excellent pharmacokinetics.

Tetrahydroindolizinone NK1 antagonists.

A new class of potent NK(1) receptor antagonists with a tetrahydroindolizinone core has been identified. This series of compounds demonstrated improved functional activities as compared to previously identified 5,5-fused pyrrolidine lead structures. SAR at the 7-position of the tetrahydroindolizinone core is discussed in detail. A number of compounds displayed high NK(1) receptor occupancy at both 1 h and 24 h in a gerbil foot tapping model. Compound 40 has high NK(1) binding affinity, good selectivity for other NK receptors and promising in vivo properties. It also has clean P(450) inhibition and hPXR induction profiles.

p38 MAP kinase inhibitors: metabolically stabilized piperidine-substituted quinolinones and naphthyridinones.

Quinolinones and naphthyridinones with C7 N-t-butyl piperidine substituents were found to be potent p38 MAP kinase inhibitors. These compounds significantly suppress TNF-alpha release in both cellular and LPS-stimulated whole blood assays. They also displayed excellent PK profiles across three animal species. Quinolinone at 10 mpk showed comparable oral efficacy to that of dexamethasone at 1 mpk in a murine collagen-induced arthritis model.

Potent Kv1.3 inhibitors from correolide-modification of the C18 position.

Kv1.3, the voltage-gated potassium channel in human T cells, represents a new target for treating immunosuppression and autoimmune diseases. Correolide (1), a pentacyclic natural product, is a potent and selective Kv1.3 channel blocker. Simplification of correolide via removal of its E-ring generates enone 4, whose modification produced a new series of tetracyclic Kv1.3 blockers. The structure-activity relationship for this class of compounds in two functional assays, Rb_Kv and human T cell proliferation, is presented herein. The most potent analog 43 is 15-fold more potent than correolide as inhibitor of human T cell proliferation.

[A comparative study on iodine nutritional status of adult islanders in Zhoushan].

OBJECTIVE: To measure the iodine nutritional status on adult islanders and to evaluate the advantages and disadvantages of iodized salt prophylactic programs. METHODS: A comparative study was carried out in 8 rural townships selected from Dinghai (iodized salt district) and Daishan (non-iodized salt district) of Zhoushan islands by random sampling method. Mann-Whitney test was used to compare the urinary iodine concentration and dietary iodine intake of the two groups. Spearman correlation test was used to look for the correlation of urinary iodine concentration and dietary iodine intake in the two groups respectively. RESULTS: The amounts of daily iodine intake excluding the iodine intake from iodized salt in the two groups were 128 micro g and 147 micro g respectively but the difference was not statistically significant (u = 1.847, P = 0.065). The urinary iodine concentration of non-iodized salt group was 90 micro g/L, lower than 194 micro g/L in iodized salt group (u = 14.673, P = 0.000). There was no significant correlation between daily iodine intake and urinary iodine concentration (r(s) = 0.052, P = 0.095). CONCLUSIONS: In Zhoushan islands, the daily iodine intake did not meet the daily need (150 micro g/day) suggesting that iodized salt supplement was necessary. However, side effect due to overdose should be brought into attention.

Benzamide derivatives as blockers of Kv1.3 ion channel.

The voltage-gated potassium channel, Kv1.3, is present in human T-lymphocytes. Blockade of Kv1.3 results in T-cell depolarization, inhibition of T-cell activation, and attenuation of immune responses in vivo. A class of benzamide Kv1.3 channel inhibitors has been identified. The structure-activity relationship within this class of compounds in two functional assays, Rb_Kv and T-cell proliferation, is presented. In in vitro assays, trans isomers display moderate selectivity for binding to Kv1.3 over other Kv1.x channels present in human brain.

Identification of a new class of inhibitors of the voltage-gated potassium channel, Kv1.3, with immunosuppressant properties.

The voltage-gated potassium channel, K(v)1.3, is a novel target for development of immunosuppressants. Using a functional (86)Rb(+) efflux assay, a new class of high-affinity K(v)1.3 inhibitors has been identified. The initial active in this series, 4-phenyl-4-[3-(2-methoxyphenyl)-3-oxo-2-azaprop-1-yl]cyclohexanone (PAC), which is representative of a disubstituted cyclohexyl (DSC) template, displays a K(i) of ca. 300 nM and a Hill coefficient near 2 in the flux assay and in voltage clamp recordings of K(v)1.3 channels in human T-lymphocytes. PAC displays excellent specificity as it only blocks members of the K(v)1 family of potassium channels but does not affect many other types of ion channels, receptors, or enzyme systems. Block of K(v)1.3 by DSC analogues occurs with a well-defined structure-activity relationship. Substitution at the C-1 ketone of PAC generates trans (down) and cis (up) isomer pairs. Whereas many DSC derivatives do not display selectivity in their interaction with different K(v)1.x channels, trans DSC derivatives distinguish between K(v)1.x channels based on their rates of C-type inactivation. DSC analogues reversibly inhibit the Ca(2+)-dependent pathway of T cell activation in in vitro assays. Together, these data suggest that DSC derivatives represent a new class of immunosuppressant agents and that specific interactions of trans DSC analogues with channel conformations related to C-type inactivation may permit development of selective K(v)1.3 channel inhibitors useful for the safe treatment of autoimmune diseases.

Novel fragmentation reaction of correolide.

[reaction: see text] Pentacyclic triterpenoid natural product correolide (1) was converted to ketone 2 via ozonolysis. An unusual fragmentation reaction of ketone 2 with LiCl was discovered. This reaction is general among several similar substrates examined and appears to be specific for the correolide-type E-ring structure (ketone). A mechanism involving a retroaldol reaction, a nucleophilic opening of the epoxide, and a subsequent acetoxy elimination reaction was proposed.

Selective Inversion of the Proximal or Distal Hydroxyl Groups in syn,syn-3-[N-(Alkoxycarbonyl)amino] 1,2-Diols via Cyclic Sulfates.

The formation of cyclic sulfates (4) from syn,syn-3-[N-(benzyloxycarbonyl)amino] 1,2-diols provides a common intermediate to access other diastereomers via two inversion procedures. Thermolysis of the cyclic sulfates in acetonitrile normally leads to inversion of the distal hydroxyl group to form a 1,3-oxazin-2-one (6). Catalytic hydrogenation of the cyclic sulfates under basic conditions (NEt(3)) results in inversion at the proximal hydroxyl group to form a 1,3-oxazolidin-2-one (5).