Direct radical functionalization methods to access substituted adamantanes and diamondoids.

Adamantane derivatives have diverse applications in the fields of medicinal chemistry, catalyst development and nanomaterials, owing to their unique structural, biological and stimulus-responsive properties, among others. The synthesis of substituted adamantanes and substituted higher diamondoids is frequently achieved via carbocation or radical intermediates that have unique stability and reactivity when compared to simple hydrocarbon derivatives. In this review, we discuss the wide range of radical-based functionalization reactions that directly convert diamondoid C-H bonds to C-C bonds, providing a variety of products incorporating diverse functional groups (alkenes, alkynes, arenes, carbonyl groups, etc.). Recent advances in the area of selective C-H functionalization are highlighted with an emphasis on the H-atom abstracting species and their ability to activate the particularly strong C-H bonds that are characteristic of these caged hydrocarbons, providing insights that can be applied to the C-H functionalization of other substrate classes.

Isolating α-Pinene Ozonolysis Pathways Reveals New Insights into Peroxy Radical Chemistry and Secondary Organic Aerosol Formation.

α-Pinene ozonolysis is a key process that impacts the formation of new particles and secondary organic aerosol (SOA) in the atmosphere. The mechanistic understanding of this chemistry has been inconclusive despite extensive research, hindering accurate simulations of atmospheric processes. In this work, we examine the ozonolysis of two synthesized unsaturated carbonyl isomers (C11H18O) which separately produce the two Criegee intermediates (CIs) that would form simultaneously in α-pinene ozonolysis. Direct gas-phase measurements of peroxy radicals (RO2) from flowtube ozonolysis experiments by an iodide-adduct chemical ionization mass spectrometer suggest that the initial C10H15O4· RO2 from the CI with a terminal methyl ketone undergo autoxidation 20-fold faster than the CI with a terminal aldehyde and always outcompete the bimolecular reactions under typical laboratory and atmospheric conditions. These results provide experimental constraints on the detailed RO2 autoxidation mechanisms for understanding new particle formation in the atmosphere. Further, isomer-resolved characterization of the SOA formed from a continuous-flow stirred tank reactor using ion mobility spectrometry mass spectrometry suggests that the two structurally different CIs predominantly and unexpectedly form constituents with identical structures. These results open up possibilities of diverse isomerization pathways that the two CIs may undergo that form mutual products to a large extent toward their way forming the SOA. This work highlights new insights into α-pinene ozonolysis pathways and call for future studies to uncover the detailed mechanisms.

Synthesis and Structure Reassignment of Malylglutamate, a Recently Discovered Earthworm Metabolite.

Malylglutamate, a newly identified metabolite in earthworms, was synthesized using a traditional peptide coupling approach for assembling the amide from protected malate and glutamate precursors. The proposed structure (1) and a diastereomer were synthesized, but their NMR spectra did not match the natural sample. Further analysis of the natural sample using HMBC spectroscopy suggested an alternative attachment of the malyl moiety, and ß-malylglutamate (2) diastereomers were synthesized, L,L-2 and D,D-2. NMR spectra were an excellent match with the natural sample, and chiral-phase chromatography was employed to identify (-)-ß-l-malyl-l-glutamate (2) as the isomer native to Eisenia fetida.

Interdisciplinary pharmacometrics linking oseltamivir pharmacology, influenza epidemiology and health economics to inform antiviral use in pandemics.

AIMS: A modular interdisciplinary platform was developed to investigate the economic impact of oseltamivir treatment by dosage regimen under simulated influenza pandemic scenarios. METHODS: The pharmacology module consisted of a pharmacokinetic distribution of oseltamivir carboxylate daily area under the concentration-time curve at steady state (simulated for 75 mg and 150 mg twice daily regimens for 5 days) and a pharmacodynamic distribution of viral shedding duration obtained from phase II influenza inoculation data. The epidemiological module comprised a susceptible, exposed, infected, recovered (SEIR) model to which drug effect on the basic reproductive number (R0 ), a measure of transmissibility, was linked by reduction of viral shedding duration. The number of infected patients per population of 100 000 susceptible individuals was simulated for a series of pandemic scenarios, varying oseltamivir dose, R0 (1.9 vs. 2.7), and drug uptake (25%, 50%, and 80%). The number of infected patients for each scenario was entered into the health economics module, a decision analytic model populated with branch probabilities, disease utility, costs of hospitalized patients developing complications, and case-fatality rates. Change in quality-adjusted life years was determined relative to base case. RESULTS: Oseltamivir 75 mg relative to no treatment reduced the median number of infected patients, increased change in quality-adjusted life years by deaths averted, and was cost-saving under all scenarios; 150 mg relative to 75 mg was not cost effective in low transmissibility scenarios but was cost saving in high transmissibility scenarios. CONCLUSION: This methodological study demonstrates proof of concept that the disciplines of pharmacology, disease epidemiology and health economics can be linked in a single quantitative framework.

Selective C-H Activation of Molecular Nanodiamonds via Photoredox Catalysis.

While substituted adamantanes have widespread use in medicinal chemistry, materials science, and ligand design, the use of diamantanes and higher diamondoids is limited to a much smaller number. Selective functionalization beyond adamantane is challenging, as the number of very similar types of C-H bonds (secondary, 2°, and tertiary, 3°) increases rapidly, and H atom transfer does not provide a general solution for site selectivity. We report a method using pyrylium photocatalysts that is effective for nanodiamond functionalization in up to 84% yield with exclusive 3° selectivity and moderate levels of regioselectivity between 3° sites. The proposed mechanism involving photooxidation, deprotonation, and radical C-C bond formation is corroborated through Stern-Volmer luminescence quenching, cyclic voltammetry, and EPR studies. Our photoredox strategy offers a versatile approach for the streamlined synthesis of diamondoid building blocks.

A Novel Analog of the Natural Product Fraxinellone Protects against Endogenous and Exogenous Neurotoxicants.

Numerous insults, both endogenous (e.g., glutamate) and exogenous (e.g., pesticides), compromise the function of the nervous system and pose risk factors for damage or later disease. In previous reports, limonoids such as fraxinellone showed significant neuroprotective activity against glutamate (Glu) excitotoxicity and reactive oxygen species (ROS) production in vitro, albeit with minimal mechanistic information provided. Given these findings, a library of novel fraxinellone analogs (including analogs 1 and 2 described here) was synthesized with the goal of identifying compounds exhibiting neuroprotection against insults. Analog 2 was found to be protective against Glu-mediated excitotoxicity with a measured EC50 of 44 and 39 nM for in vitro assays using PC12 and SH-SY5Y cells, respectively. Pretreatment with analog 2 yielded rapid induction of antioxidant genes, namely, Gpx4, Sod1, and Nqo1, as measured via qPCR. Analog 2 mitigated Glu-mediated ROS. Cytoprotection could be replicated using sulforaphane (SFN), a Nrf2 activator, and inhibited via ML-385, which inhibits Nrf2 binding to regulatory DNA sequences, thereby blocking downstream gene expression. Nrf2 DNA-binding activity was demonstrated using a Nrf2 ELISA-based transcription factor assay. In addition, we found that pretreatment with the thiol N-acetyl Cys completely mitigated SFN-mediated induction of antioxidant genes but had no effect on the activity of analog 2, suggesting thiol modification is not critical for its mechanism of action. In summary, our data demonstrate a fraxinellone analog to be a novel, potent, and rapid activator of the Nrf2-mediated antioxidant defense system, providing robust protection against insults.

Syntheses of strychnine, norfluorocurarine, dehydrodesacetylretuline, and valparicine enabled by intramolecular cycloadditions of Zincke aldehydes.

A full account of the development of the base-mediated intramolecular Diels-Alder cycloadditions of tryptamine-derived Zincke aldehydes is described. This important complexity-generating transformation provides the tetracyclic core of many indole monoterpene alkaloids in only three steps from commercially available starting materials and played a key role in short syntheses of norfluorocurarine (five steps), dehydrodesacetylretuline (six steps), valparicine (seven steps), and strychnine (six steps). Reasonable mechanistic possibilities for this reaction, a surprisingly facile dimerization of the products, and an unexpected cycloreversion to regenerate Zincke aldehydes under specific conditions are also discussed.

Concise synthesis of (-)-nakadomarin†A.

The beautiful orchestration of new methods and synthesis design was instrumental to the very efficient synthesis of the manzamine alkaloid (-)-nakadomarin A. In only six operations, the two relatively simple compounds shown were converted into the hexacyclic natural product.

Synthesis of amino-diamondoid pharmacophores via photocatalytic C-H aminoalkylation.

We report a direct C-H aminoalkylation reaction using two light-activated H-atom transfer catalyst systems that enable the introduction of protected amines to native adamantane scaffolds with C-C bond formation. The scope of adamantane and imine reaction partners is broad and deprotection provides versatile amine and amino acid building blocks. Using readily available chiral imines, the enantioselective synthesis of the saxagliptin core and rimantadine derivatives is also described.

Efficient access to the core of the Strychnos, Aspidosperma and Iboga alkaloids. A short synthesis of norfluorocurarine.

An efficient anionic bicyclization of tryptamine-derived Zincke aldehydes forms the basis for a three-step route to the tetracyclic ABCE core of many Strychnos, Aspidosperma, and Iboga alkaloids. This powerful reaction is showcased in a five-step synthesis of the Strychnos alkaloid norfluorocurarine from tryptamine and pyridine.

Recent insights into natural product inhibitors of matrix metalloproteinases.

Members of the matrix metalloproteinase (MMP) family have biological functions that are central to human health and disease, and MMP inhibitors have been investigated for the treatment of cardiovascular disease, cancer and neurodegenerative disorders. The outcomes of initial clinical trials with the first generation of MMP inhibitors proved disappointing. However, our growing understanding of the complexities of the MMP function in disease, and an increased understanding of MMP protein architecture and control of activity now provide new opportunities and avenues to develop MMP-focused therapies. Natural products that affect MMP activities have been of strong interest as templates for drug discovery, and for their use as chemical tools to help delineate the roles of MMPs that still remain to be defined. Herein, we highlight the most recent discoveries of structurally diverse natural product inhibitors to these proteases.

Real-world evidence of improved healthcare utilization in patients with schizophrenia or schizoaffective disorder after early treatment of paliperidone palmitate once-monthly treatment in Hong Kong.

BACKGROUND: Very few data are available to demonstrate the economic benefit of early paliperidone palmitate once-monthly long-acting injectable (PP1M) treatment in patients with schizophrenia or schizoaffective disorder. METHODS AND MATERIALS: This study has retrospectively compared the healthcare utilization and associated costs of pre- and post-PPIM treatment in 413 patients with schizophrenia or schizoaffective disorder recruited from three major public hospitals providing psychiatric services in Hong Kong. Patients were categorized into early treatment (≤3 years since diagnosis) and chronic (>3 years) groups, and also whether they were receiving polypharmacy (POP). RESULTS: It was found that patients who were started on early therapy with no POP had the most favourable outcomes. Overall results of the entire cohort, including both early and late treatments, indicate that there was a slight increase in annual in-patient days (IP) per patient and outpatient visit (OP) by 3.18 and 1.87, respectively, and a decrease in emergency room visit (ER) of 0.9 (p < 0.05). For non-polypharmacy (NP) patients receiving early PP1M therapy, there was a significant decrease in IP and ER of 21.56 (p < 0.05) and 1.15 (p < 0.05), respectively, but an increase in OP of 1.88 (p < 0.05). For patients with POP, there was an all-across increase in IP and all-across decrease in OP and ER. In monetary terms, a NP patient receiving early therapy may have an overall saving of HKD40,878 (USD5,241, 1USD = 7.8HKD) per year compared to HKD6,224 (USD798) in patients where therapy was given after 3 years. For patients with POP, there was an all-across increase in overall spending despite reductions in OP and ER. CONCLUSIONS: From the 413 patients studied, potential annual savings is higher by early administration of PPIM in patients with NP. Analysis using multivariate linear regression based on generalized estimating equations and sensitivity analysis using a linear mixed model supported the findings.

Unexpected Alkene Isomerization during Iterative Cross-Coupling To Form Hindered, Electron-Deficient Trienes.

An iterative cross-coupling approach to conjugated trienes was explored as part of a planned stereoselective synthesis of bicyclic terpenes. Using a bifunctional bromoboronate building block, sequential Suzuki coupling reactions were employed to provide a conjugated trienone target containing a tetrasubstituted alkene. During the final cross-coupling step, an unexpected alkene isomerization was observed to give less hindered trans products. Examination of different substrates determined that conjugation to a ketone withdrawing group was responsible for isomerization, rather than steric hindrance of the tetrasubstituted alkene.

A Heck-Based Strategy To Generate Anacardic Acids and Related Phenolic Lipids for Isoform-Specific Bioactivity Profiling.

A synthetic strategy for phenolic lipids such as anacardic acid and ginkgolic acid derivatives using an efficient and selective redox-relay Heck reaction followed by a stereoselective olefination is reported. This approach controls both the alkene position and stereochemistry, allowing the synthesis of natural and unnatural unsaturated lipids as single isomers. By this strategy, the activities of different anacardic acid and ginkgolic acid derivatives have been examined in a matrix metalloproteinase inhibition assay.

Cytotoxic activity in broth-culture filtrates of Campylobacter pylori.

Broth-culture filtrates of Campylobacter pylori induced non-lethal cytopathic effects in vitro in 7 of 9 mammalian cell lines tested. Transmission electronmicroscopy revealed that the response consisted of intracellular vacuolisation. Intestine 407 cells were among the most responsive and were used for routine assay. About 55% of isolates of C. pylori tested, originating from four geographic regions worldwide, produced cytotoxic activity. The activity was neutralisable by specific antisera to broth-culture filtrates or to sonicated bacteria but not by antisera to other bacterial preparations. Cytotoxic activity was heat-labile (70 degrees C for 30 min), was protease-sensitive and ammonium-sulphate precipitable. It did not pass through an ultrafiltration membrane with a nominal mol.-wt limit of 100 X 10(3). It was concluded that C. pylori can produce a factor that alters cultured cells in vitro. The relevance of this factor to the pathogenesis of gastritis associated with C. pylori remains to be determined.

Photoredox activation for the direct ß-arylation of ketones and aldehydes.

The direct ß-activation of saturated aldehydes and ketones has long been an elusive transformation. We found that photoredox catalysis in combination with organocatalysis can lead to the transient generation of 5π-electron ß-enaminyl radicals from ketones and aldehydes that rapidly couple with cyano-substituted aryl rings at the carbonyl ß-position. This mode of activation is suitable for a broad range of carbonyl ß-functionalization reactions and is amenable to enantioselective catalysis.

The Intramolecular Diels-Alder Reaction of Tryptamine-Derived Zincke Aldehydes Is a Stepwise Process.

Computational studies show that the base-mediated intramolecular Diels-Alder of tryptamine-derived Zincke aldehydes, used as a key step in the synthesis of the Strychnos alkaloids norfluorocurarine and strychnine, proceeds via a stepwise pathway. The experimentally determined importance of a potassium counterion in the base is explained by its ability to preorganize the Zincke aldehyde diene in an s-cis conformation suitable to bicyclization. Computation also supports the thermodynamic importance of the generation of a stable enolate in the final reaction step. The thermal cycloreversion reaction of the Diels-Alder products is also found to proceed in a stepwise manner.

Cutaneous infection in normal and immunocompromised mice.

Since a model of staphylococcal skin infection adequately reflecting human disease was unavailable, a self-limiting animal infection model specific for virulent Staphylococcus species was developed. A virulent strain of S. aureus, NCTC 9789 (ATCC 27700), was used to develop an infection model in adult, male CF-1 mice treated with 0 to 150 mg of cyclophosphamide (CY) per kg 4 days before challenge. Bacteria were inoculated onto the dorsal side of shaved mice at 0 to 10(6) CFU per mouse. Simultaneously, the skin was gently scraped to remove the superficial layers without drawing blood. The wound was occluded with impermeable film secured with surgical tape. At a CY dose of 50 mg/kg and an inoculum of 10(5) CFU, 89% of the mice (96 of 108) developed large abscesses (approximately 15-mm diameter). Mice which were not immunocompromised developed fewer abscesses (20 of 68). Generally, no abscesses formed when the mice were not wounded (1 of 62), occluded (0 of 89), or inoculated (11 of 50). The abscesses developed 24 to 48 h after challenge and persisted for 2 to 3 weeks. The challenge organism was isolated from the abscesses. The rates of abscess formation of three additional S. aureus strains varied widely in normal and CY-treated mice. Three strains of S. epidermidis, one of Micrococcus varians, and one of S. saprophyticus failed to cause abscesses. Bacterial proliferation studies demonstrated that a strain of S. aureus and a strain of S. epidermidis proliferated to the same levels 48 h after challenge. Immunosuppression and wounding had little effect on the levels of proliferation of S. aureus (P greater than 0.2). Without occlusion, however, S. aureus proliferated to significantly lower levels (P less than 0.005). This model may be be useful for screening topical anti-infective agents or studying the mechanisms of bacterial pathogenesis and host response.