Discovery of Spilanthol Endoperoxide as a Redox Natural Compound Active against Mammalian Prx3 and Chlamydia trachomatis Infection.

Chlamydia trachomatis (Ct) is a bacterial intracellular pathogen responsible for a plethora of diseases ranging from blindness to pelvic inflammatory diseases and cervical cancer. Although this disease is effectively treated with antibiotics, concerns for development of resistance prompt the need for new low-cost treatments. Here we report the activity of spilanthol (SPL), a natural compound with demonstrated anti-inflammatory properties, against Ct infections. Using chemical probes selective for imaging mitochondrial protein sulfenylation and complementary assays, we identify an increase in mitochondrial oxidative state by SPL as the underlying mechanism leading to disruption of host cell F-actin cytoskeletal organization and inhibition of chlamydial infection. The peroxidation product of SPL (SPL endoperoxide, SPLE), envisioned to be the active compound in the cellular milieu, was chemically synthesized and showed more potent anti-chlamydial activity. Comparison of SPL and SPLE reactivity with mammalian peroxiredoxins, demonstrated preferred reactivity of SPLE with Prx3, and virtual lack of SPL reaction with any of the reduced Prx isoforms investigated. Cumulatively, these findings support the function of SPL as a pro-drug, which is converted to SPLE in the cellular milieu leading to inhibition of Prx3, increased mitochondrial oxidation and disruption of F-actin network, and inhibition of Ct infection.

Photochemical Synthesis of Nepetanudone.

Nepetanudone and nepetaparnone have been suspected of being the products of a photochemical dimerization of nepetapyrone. Both are natural products found in a variety of Nepeta species. The synthesis of (±)-nepetapyrone and subsequent photochemical experiments are described. (±)-Nepetanudone was produced upon irradiation of (±)-nepetapyrone, while (±)-nepetaparnone, a diastereomer of nepetanudone, was not observed.

The correct structure of aquatolide-experimental validation of a theoretically-predicted structural revision.

Aquatolide has been reisolated from its natural source, and its structure has been revised on the basis of quantum-chemical NMR calculations, extensive experimental NMR analysis, and crystallography.

Photochemistry of 1,n-dibenzyloxy-9,10-anthraquinones.

The photochemistry of a series of 9,10-anthraquinones with multiple benzyloxy substituents was investigated. In polar solvent, the expected Blankespoor oxidative cleavage reaction is the major reaction pathway, but in most cases, several minor products were observed. In nonpolar solvents, the abundance of these minor products increases dramatically. Four types of product were observed with the favored reaction pathway shifting with minor changes in substitution on the anthraquinone. Several types of product require cleavage of the C-O bond on the benzyloxy group and, apparently, follow a photo-Claisen-type mechanism. Others involve the expected 1,5-diradical but do not exhibit the single-electron transfer usually observed in the Blankespoor-type reaction. The results indicate the importance of considering the medium and photoredox behavior in anthraquinone photochemistry.

Photochemical hydroxylation of 1-methyl-9,10-anthraquinones: synthesis of 9'-hydroxyaloesaponarin II.

Photolysis of 1-methyl-9,10-anthraquinones in the presence of oxygen yields endoperoxides that can be reduced to produce 1-hydroxymethyl-9,10-anthraquinones. The reaction proceeds in a fashion similar to that of other o-alkylphenones which yield either a 1,4-diradical or a "photoenol" upon irradiation. Anthraquinones undergo photochemistry at a wavelength where the endoperoxide is transparent, allowing its isolation. A singlet oxygen quencher had no effect on the rate of formation of the endoperoxide. The photochemical hydroxylation has been used in a total synthesis of a naturally occurring polyketide, 9'-hydroxyaloesaponarin II.

Observation of heavy atom effects in the development of water soluble caged 4-hydroxy-trans-2-nonenal.

During the course of our study on the photochemistry of 1-alkoxy-9,10-anthraquinones, we have developed a second generation of a caged 4-hydroxy-trans-2-nonenal (4-HNE). As we optimized the anthraquinonyl chromophore to achieve water solubility, we studied the photochemistry of various substituents to understand their effect on the photochemistry. We observed a significant heavy atom effect that severely reduced the rate of oxidative cleavage of the alkoxy group. Based on the results of our substituent study, we designed a new caged 4-HNE that is soluble under physiological conditions, and that releases 4-HNE photochemically in high yield.

Photosensitized tetrahydropyran transfer.

THP ethers were formed cleanly during photolysis of 3,4-dihydro-2 H-pyran, an alcohol, and catalytic 1,5-dichloro-9,10-anthraquinone with use of visible light. The reaction could be conducted under ambient fluorescent lighting or with sunlight as well as in a Rayonet reactor. The scope and mechanism are discussed.

Triplet photosensitization in cyercene A and related pyrones.

Mollusks of the Sacoglossa order contain a variety of polypropionate metabolites that are characterized by a pyrone chromophore, such as cyercene A and 9,10-deoxytridachione. Most often the pyrone is a 2-methoxy-gamma-pyrone but occasionally is a 4-methoxy-alpha-pyrone or hydropyrone. Members of this class of metabolites have been shown to undergo photochemical reactions of biosynthetic importance. An example is the photochemical conversion of 9,10-deoxytridachione to photodeoxytridachione, which has been observed in several mollusks. In this report, a series of gamma-pyrones and their alpha-pyrone analogs were synthesized and analyzed for photosensitizing activity. In all cases studied, the gamma-pyrone was a more efficient triplet sensitizer than the corresponding alpha-pyrone. Included in this set of molecules was the Sacoglossan metabolite cyercene A and its alpha-pyrone isomer. When irradiated in the presence of oxygen, cyercene A produced singlet oxygen at significantly higher rate than the corresponding alpha-pyrone isomer. Furthermore, the photoisomerization of cyercene A was quenched by piperylene with con-committant isomerization of the piperylene indicating that the isomerization proceeded through a triplet excited state. In contrast, the isomerization of the alpha-pyrone analog was not quenched. The implications of these photochemical results in terms of the biosynthesis and biological activity of Sacoglossan polypropionate metabolites are discussed.

Photosensitized conversion of 9,10-deoxytridachione to photodeoxytridachione.

[reaction: see text] The photochemical conversion of 9,10-deoxytridachione to photodeoxytridachione has been photosensitized. The conversion was also quenched by piperylene. Photodeoxytridachione was produced in good yields under conditions in which only the cyclohexadiene group is sensitized. The results show that some, and perhaps all, of the photoreactions of 9,10-deoxytridachione occur through a triplet excited state. The mechanistic and biosynthetic implications of these results are discussed.

Photochemical relationships in Sacoglossan polypropionates.

Cyercene A has been synthesized and converted to placidene A and isoplacidene A through photoisomerization with sunlight. Hydroperoxide, isolated form Placida dendritica, was synthesized both by singlet oxygenation of cyercene A using Rose Bengal and through the irradiation of cyercene A alone in aerobic solution. The observation that hydroperoxide could be made by singlet oxygenation of cyercene A and that this occurs when cyercene A alone is irradiated supported the hypothesis that gamma-pyrones may act as triplet sensitizers. This was confirmed using cyercene A and a model gamma-pyrone to sensitize the photooxidation of n-butyl sulfide. The biosynthetic implications of these observations for Sacoglossan polypropionates are discussed.

Caged trans-4-hydroxy-2-nonenal.

[reaction: see text] A caged 4-hydroxy-2-nonenal (4-HNE) has been prepared and its photochemistry investigated. Upon photolysis, 1 releases 4-HNE in up to 100% yield. From these photolyses, 4-HNE could be isolated in up to 91% yield. 4-HNE is produced under either aerobic or anaerobic conditions. The caging strategy does not require prior preparation of 4-HNE and, therefore, represents a three-step synthetic route to the bioactive enal in 48% overall yield.

Growth, Congo Red agar colony morphotypes and antibiotic susceptibility testing of Mycobacterium avium subspecies paratuberculosis.

OBJECTIVE: Mycobacterium avium subspecies (subsp.) paratuberculosis (MAP) is the causative agent of Johne's disease in ruminants and has been associated with Crohn's disease in humans. We sought to test growth rates and susceptibilities of various strains of MAP in two available growth media. DESIGN: Paired comparison design. METHODS: Using the BACTEC macrobroth radiometric growth system and Congo Red-staining agar media, we determined inherent differences in growth characteristics of three bovine and two human strains of MAP and compared susceptibility results obtained in each growth system. RESULTS: Significant differences were observed in growth rate as well as mycobactin J dependence between strains and between a laboratory-adapted isolate of the same strain in the macrobroth system. Similarly, colonial morphology and Congo Red staining on agar media were observed. Two strains, one human and one bovine, demonstrated a 100% rough transparent colony with white coloration on Congo Red agar, while one bovine isolate exclusively grew as a smooth opaque colony with red coloration on Congo Red agar. The remaining strains exhibited mixtures of these two colonial morphotypes on agar media. Comparative susceptibility results between the BACTEC radiometric macrobroth method and the agar proportionality method showed good correlation for most antibiotics/inhibitors tested. However, erratic or poor growth in the macrobroth system prevented minimal inhibitory concentration determinations for two bovine strains by this method. CONCLUSION: This study demonstrates the variability in the colonial morphology of MAP on Congo Red agar as well as the correlation of antibiotic susceptibility results between the BACTEC macro broth method and the agar proportionality method. This study also emphasizes the need for the development of improved, standardized culture and susceptibility test methods for MAP.

Photoreduction of benzophenones by amines in room-temperature ionic liquids.

[reaction: see text] The amine-mediated photoreduction of benzophenones in room temperature ionic liquids was investigated. Unlike the analogous reaction in organic solvents, the photoreduction produces mainly the corresponding benzhydrol in most cases. Because the reaction consumes only 1 equiv of amine and the solvent can be easily recycled, the photoreduction allows a very clean method for the conversion of benzophenones to benzhydrols.

2,2,3-Trisubstituted Tetrahydrofurans and 2H-Tetrahydropyrans by Tandem Demethoxycarbonylation-Michael Addition Reactions.

A tandem demethoxycarbonylation-Michael addition reaction has been developed as a synthetic route to highly functionalized five- and six-membered oxygen heterocycles. Methyl esters, activated toward decarboxylation by a C-2 ethoxycarbonyl group and tethered by a three- or four-atom chain to an acrylate Michael acceptor, have been prepared and used as the cyclization substrates. Treatment of these compounds with lithium chloride in DMEU (1,3-dimethyl-2-imidazolidinone) at 120 degrees C for 4-8 h results in chemoselective S(N)2 dealkylation of the methyl esters, decarboxylation, and cyclization of the intermediate enolates by a Michael addition to the pendent acrylate moiety. This affords tetrahydrofuran and 2H-tetrahydropyran derivatives in 60-90% yields with diastereoselectivities up to 7.5:1 in favor of the product having the C-2 ethoxycarbonyl group trans to the C-3 acetic ester side chain. The reaction works best for the preparation of five- and six-membered rings, and cyclizations proceed most cleanly from substrates which cyclize through a tertiary enolate. Synthetic and mechanistic details are presented.