Bifunctional catalysis in zeolites possessing both Brønsted and Lewis acid sites offers unique opportunities to tailor shape selectivity and enhance catalyst performance. Here, we examine the impact of framework and extra-framework gallium species on enriched aromatics production in zeolite ZSM-5. We compare three distinct methods of preparing Ga-ZSM-5 and reveal direct (single step) synthesis leads to optimal catalysts compared to post-synthesis methods. Using a combination of state-of-the-art characterization, catalyst testing, and density functional theory calculations, we show that Ga Lewis acid sites strongly favor aromatization. Our findings also suggest Ga(framework)–Ga(extra-framework) pairings, which can only be achieved in materials prepared by direct synthesis, are the most energetically favorable sites for reaction pathways leading to aromatics. Calculated acid site exchange energies between extra-framework Ga at framework sites comprised of either Al or Ga reveal a site-specific preference for stabilizing Lewis acids, which is qualitatively consistent with experimental measurements. These findings indicate the possibility of tailoring Lewis acid siting by the placement of Ga heteroatoms at distinct tetrahedral sites in the zeolite framework, which can have a marked impact on catalyst performance relative to conventional H-ZSM-5.

Coupling of organic and inorganic chemistry presents a new degree of freedom in nano-engineering of thermomechanical properties of cement-based materials. Despite these vast technological benefits, molecular scale cross-linking of calcium-silicate-hydrate (C-S-H) gel with organic molecules still presents a significant challenge. Herein, we report experimental results on sol-gel synthesis, structure and morphology of nanocrystalline C-S-H cross-linked with dipodal organosilanes. These novel organic-inorganic gels have layered turbostratic molecular structure with similarities to C-S-H precipitating in hydrating cement paste. The organic molecules' chain length controls the interlayer spacing, which shows little to no shrinkage upon dehydration up to 105 degrees C. However, the structure gets distorted in the basal crystallite plane, in which dimer and trimer Si-polyhedra structures condense on a 2D hexagonal Ca-polyhedra layer. Cross-linked C-S-H gels display plate-like morphology with tendency toward stacking into agglomerates at the larger scale. If successfully realized in cement environment, e.g. high concentration seed, such novel organic-inorganic C-S-H gels could potentially provide cement-based matrices with unique properties unmatched by classical inorganic systems.

We detail a polymer synthetic methodology that merges the techniques of insertion and radical polymerization methods into a single organometallic catalyst. This metal-organic insertion/light initiated radical (MILRad) polymerization technique proves successful at polymerizing methyl acrylate (MA) and hexene, using light as a critical stimulus to activate the dormant photoresponsive nature of the insertion catalyst. In this study, we describe a novel approach that uses visible light (460 nm) to switch the catalytic activity of a cationic palladium catalyst from an insertion route to a radical process when desired. We discovered that in a mixture of MA and hexene one monomer can be selectively polymerized using light and dark cycles, respectively. As a result, this polymerization process enables the copolymerization of MA and hexene to create homo- and block copolymer architectures facilitated solely by visible light. In this work, we show the synthesis of MA homopolymers in molecular weight ranges (M-n 50-400 kDa) with dispersities of similar to 1.7. Synthesis of MA (A) and hexene (B) block copolymers were accomplished with a single catalyst in both a sequential and novel one-pot approach, relying solely upon visible light irradiation. A series of BA block copolymers were prepared with tunable monomer compositions, molecular weight ranges of (M-n 11-36 kDa), and well-controlled polydispersities (similar to 1.3-1.6) in a robust rapid synthesis. MILRad polymerization circumvents the need for quantitative conversions during block formation afforded by the orthogonal monomer reactivity dependent upon a light stimulus to acquire distinct polymer architectures with variable block compositions. The use of a photocontrollable "switch" affecting a single organometallic catalyst allows access to block polymers from nonpolar and polar olefins in a novel and facile approach.

The Candida albicans fitness test is a whole cell screening platform that utilizes a mixed-pool of C. albicans mutants, each of which carries a heterozygous deletion of a particular gene. In the presence of an antifungal inhibitor, a subset of these mutants exhibits a growth phenotype of hypersensitivity or hyposensitivity. Collectively these mutants reflect aspects of the mechanism of action of the compound in question. In the course of screening natural products a culture of Streptomyces sp. MS-1-4 was discovered to produce a compound, dretamycin, which yielded a fitness profile exhibiting significant hypersensitivity of the DRE2 heterozygote and hyposensitivity of the DIP5 heterozygote. Herein we report the production, isolation, and structure elucidation of dretamycin.

The ever-increasing bacterial resistance to clinical antibiotics is making many drugs ineffective and creating significant treatment gaps. This can be only circumvented by the discovery of antibiotics with new mechanisms of action. We report here the identification of a new tetramic acid, ascosetin, from an Ascomycete using the Staphylococcus aureus fitness test screening method. The structure was elucidated by spectroscopic methods including 2D NMR and HRMS. Relative stereochemistry was determined by ROESY and absolute configuration was deduced by comparative CD spectroscopy. Ascosetin inhibited bacterial growth with 2–16 μg ml −1 MIC values against Gram-positive strains including methicillin-resistant S. aureus . It also inhibited the growth of Haemophilus influenzae with a MIC value of 8 μg ml −1 . It inhibited DNA, RNA, protein and lipid synthesis with similar IC 50 values, suggesting a lack of specificity; however, it produced neither bacterial membrane nor red blood cell lysis. It showed selectivity for bacterial growth inhibition compared with fungal but not mammalian cells. The isolation, structure and biological activity of ascosetin have been detailed here.

Emergence of bacterial resistance has eroded the effectiveness of many life saving antibiotics leading to an urgent need for new chemical classes of antibacterial agents. We have applied a Staphylococcus aureus fitness test strategy to natural products screening to meet this challenge. In this paper we report the discovery of kibdelomycin A, a demethylated congener of kibdelomycin, the representative of a novel class of antibiotics produced by a new strain of Kibdelosporangium. Kibdelomycin A is a potent inhibitor of DNA gyrase and topoisomerase IV, inhibits DNA synthesis and shows whole cell antibiotic activity, albeit, less potently than kibdelomycin. Kibdelomycin C-33 acetate and tetrahydro-bisdechloro derivatives of kibdelomycin were prepared which helped define a basic SAR of the family.

Bacterial resistance to known therapeutics has led to an urgent need for new chemical classes of antibacterial agents. To address this we have applied a Staphylococcus aureus fitness test strategy to natural products screening. Here we report the discovery of kibdelomycin, a novel class of antibiotics produced by a new member of the genus Kibdelosporangium. Kibdelomycin exhibits broad-spectrum, gram-positive antibacterial activity and is a potent inhibitor of DNA synthesis. We demonstrate through chemical genetic fitness test profiling and biochemical enzyme assays that kibdelomycin is a structurally new class of bacterial type II topoisomerase inhibitor preferentially inhibiting the ATPase activity of DNA gyrase and topoisomerase IV. Kibdelomycin is thus the first truly novel bacterial type II topoisomerase inhibitor with potent antibacterial activity discovered from natural product sources in more than six decades.

Antisense-based screening strategies can be used to sensitize a microorganism and selectively detect inhibitors against a particular cellular target of interest. A strain of Staphylococcus aureus that generates an antisense RNA against SecA, a central member of the protein secretion machinery, has been used to screen for novel antibacterials. Possible inhibitors of the SecA ATP-ase were selected with a high-throughput, two-plate agar-based whole cell differential sensitivity screen. After screening a library of over 115 000 natural products extracts with the SecA antisense strain, an extract of Geomyces pannorum was identified as providing increased activity against the sensitized strain as compared with the wild-type control. Bioassay-guided isolation of the active component from this fungal extract provided a new cis-decalin secondary metabolite, which we have named pannomycin.

The Candida albicans Fitness Test, a whole-cell screening platform, was used to profile crude fermentation extracts for novel antifungal natural products with interesting mechanisms of action. An extract with intrinsic antifungal activity from the fungus Fusarium larvarum displayed a Fitness Test profile that strongly implicated mRNA processing as the molecular target responsible for inhibition of fungal growth. Isolation of the active components from this sample identified a novel class of isoxazolidinone-containing natural products, which we have named parnafungins. These natural products were isolated as an interconverting mixture of four structural- and stereoisomers. The isomerization of the parnafungins was due to a retro-Michael ring-opening and subsequent reformation of a xanthone ring system. This interconversion was blocked by methylation of an enol moiety. Structure elucidation of purified parnafungin derivatives was accomplished by X-ray crystallography and NMR analysis. The biochemical target of these natural products has been identified as the fungal polyadenosine polymerase. Parnafungins demonstrated broad spectrum antifungal activity with no observed activity against gram-positive or gram-negative bacteria. The intact isoxazolidinone ring was required for antifungal activity. In addition, the natural products were efficacious in a mouse model of disseminated candidiasis.

We isolated a cyclic lipodepsipeptide, phomafungin, from a Phoma sp. The distinct antifungal activity of phomafungin in the crude extract was initially discovered by mechanistic profiling in the Candida albicans fitness test. The purified compound contains a 28 member ring consisting of eight amino acids and a β-hydroxy-γ-methyl-hexadecanoic acid, and displays a broad spectrum of antifungal activity against Candida spp., Aspergillus fumigatus and Trichophyton mentagrophytes with MIC of 2–8μg/ml, and toxicity to mice at 25mg/kg. The linear peptide derived from opening of the lactone ring was devoid of antifungal activity as well as toxicity. Phomafungin has been identified in a number of Phoma spp. collected from Africa and the Indian and Pacific Ocean islands.

Bacterial resistance to antibiotics, particularly to multiple drug resistant antibiotics, is becoming cause for significant concern. The only really viable course of action is to discover new antibiotics with novel mode of actions. Thiazolyl peptides are a class of natural products that are architecturally complex potent antibiotics but generally suffer from poor solubility and pharmaceutical properties. To discover new thiazolyl peptides potentially with better desired properties, we designed a highly specific assay with a pair of thiazomycin sensitive and resistant strains of Staphylococcus aureus, which led to the discovery of philipimycin, a new thiazolyl peptide glycoside. It was isolated along with an acid-catalyzed degradation product by bioassay-guided fractionation. Structure of both compounds was elucidated by extensive application of 2D NMR, 1D TOCSY, and HRESIFT-MS/MS. Both compounds showed strong antibacterial activities against gram-positive bacteria including MRSA and exhibited MIC values ranging from 0.015 to 1 microg/mL. Philipimycin was significantly more potent than the degradation product. Both compounds showed selective inhibition of protein synthesis, indicating that they targeted the ribosome. Philipimycin was effective in vivo in a mouse model of S. aureus infection exhibiting an ED50 value of 8.4 mg/kg. The docking studies of philipimycin suggested that a part of the molecule interacts with the ribosome and another part with Pro23, Pro22, and Pro26 of L11 protein, which helped in explaining the differential of activities between the sensitive and resistant strains. The design and execution of the bioassay, the isolation, structure, in vitro and in vivo antibacterial activity, and docking studies of philipimycin and its degradation product are described.

A novel series of selective ligands for the human glucocorticoid receptor is described. Structure-activity studies focused on variation of B-ring size, ketal ring size, and ketal substitution. These analogs were found to be potent and selective ligands for GR and have partial agonist profiles in functional assays for transactivation (TAT, GS) and transrepression (IL-6). Of these compounds, 27, 28, and 35 were evaluated further in a mouse LPS-induced TNF-alpha secretion model. Compound 28 had an ED(50) of 14.1 mg/kg compared with 0.5 mg/kg for prednisolone in the same assay.

Neuropeptide Y (NPY) is a polypeptide found in the peripheral and central nervous system and is involved in the regulation of feeding. Antagonists of NPY receptor activation could therefore have potential for development as antiobesity drugs. Fermentation of an isolate of Xylaria persicaria yielded two novel eremophilane sesquiterpenoids xylarenals A (1) and B (2). These compounds are selective for the NPY Y5 receptor but have only modest affinity. The isolation, structure elucidation, and biological activities of these compounds are described.

Nodulisporic acid A (NAA) is an indole-diterpene natural product produced by an indeterminate species of the endophytic fungus Nodulisporium. NAA (Figure 1) is structurally related to the paspaline class of fungal metabolites. The biosynthetic origin proposed for these alkaloids involves the acetate/mevalonic acid pathway leading to geranylgeranyl pyrophosphate (GGPP). GGPP is then proposed to condense with tryptophan to form the basic indole-diterpene core. A washed cell procedure was devised to incorporate labeled precursors into NAA by a mutant Nodulisporium culture designated MF6244. Incorporation of 2-(13)C-acetate and 2-(13)C-mevalonolactone into NAA was found to occur in the classical mevalonic acid pattern. In addition to the four mevalonic acid units that form the eastern side of the molecule, three additional isoprenylations occur to form the western and southern regions of NAA. Contrary to published reports on related compounds, incubations of Nodulisporium MF6244 with (14)C- and (13)C-tryptophan showed no incorporation of label into NAA. However, high levels of incorporation into NAA were obtained with known tryptophan precursors (14)C-, (13)C-, and (15)N-anthranilic acid and (14)C- and (13)C-ribose. A novel pathway for the biosynthesis of NAA is presented.

A simple database of (13)C/(1)H-(13)C spectral lists for 11 673 natural products was created in standard commercial database format. Over 50% of the spectra were predicted using HOSE code descriptors derived from the 50% of spectra having experimental values. Prediction errors obtained by prediction of and comparison to the experimental spectra revealed an exponentially decaying dependence between the average absolute error and the depth of the matching HOSE codes. A subset of the library containing over 1000 (1)H-(13)C assigned experimental spectral lists were used to test against eight alternate query data sets. These sets represent query data from various combinations of 1D-(13)C, 1D-DEPT, and 2D-(1)H-(13)C spectra. Simulated query lists were generated using Monte Carlo methods. As expected, queries based on 2D-(1)H-(13)C data were more likely to find the correct match under unfavorable conditions.

Enfumafungin (1) is a hemiacetal, triterpene glycoside that was isolated from a fermentation of Hormonema sp. as a mixture of two interconverting forms. The primary structure of the major component of the mixture was determined as part of the mixture, mainly via NMR and comparison with hyalodendroside A (2), a related hemiacetal, triterpene glycoside that exists in a single form. The primary structure was confirmed, and the relative stereochemistry determined, based on a pair of methylacetal derivatives (3 and 4). Enfumafungin is an antifungal agent that acts as a specific inhibitor of glucan synthesis in cells and in vitro, and leads to morphological changes in yeasts and molds.

Complestatin and isomeric chloropeptin I are bicyclo hexapeptides isolated from a Streptomyces sp. Both of these compounds are inhibitors of gp120-CD4 HIV fusion activity. In this paper, we describe an efficient acid catalyzed conversion of complestatin to chloropeptin I, provide a plausible mechanism for this transformation, and unambiguously assign the stereochemistry of complestatin.

ing examination under a dissecting microscope) was the only parameter for assessing activity. The presence of more than an estimated 25% of dead larvae indicated partial activity. The presence of only live larvae in the control samples indicated inactivity. At 48 hr, only rarely were any immobile larvae observed in placebo-treated samples. Table I clearly demonstrates the activity of cyromazine, permethrin, ivermectin, and 2 experimental compounds versus L. sericata in feces collected from chickens fed medicated diets. Cyromazine at 5 ppm in the diet is the only commercially available feed-through insecticide for fly control in poultry houses. In the assay described herein, cyromazine was completely effective against first-instar L. sericata at 250 ppm and all higher levels. The high screening levels were necessary to demon- strate larvicidal activity within the 48-hr test period. Permethrin was ing examination under a dissecting microscope) was the only parameter for assessing activity. The presence of more than an estimated 25% of dead larvae indicated partial activity. The presence of only live larvae in the control samples indicated inactivity. At 48 hr, only rarely were any immobile larvae observed in placebo-treated samples. Table I clearly demonstrates the activity of cyromazine, permethrin, ivermectin, and 2 experimental compounds versus L. sericata in feces collected from chickens fed medicated diets. Cyromazine at 5 ppm in the diet is the only commercially available feed-through insecticide for fly control in poultry houses. In the assay described herein, cyromazine was completely effective against first-instar L. sericata at 250 ppm and all higher levels. The high screening levels were necessary to demon- strate larvicidal activity within the 48-hr test period. Permethrin was also as active at all levels from 1,000 ppm down to 125 ppm at the 24- hr observation. At 48 hr, the 62.5-ppm level also was lethal to the first instars. The 1,000-ppm level appeared to be well tolerated based solely on the weight gain of the treated chicks. In spite of their lack of overt toxicity, pyrethroids have not been cleared as feed-through candidates, although they are effective as manure topicals. Phenothiazine was the first antiparasitic agent on record that was inadvertently successful as a feed-through insecticide (Knipling, 1938). In his attempt to control screwworm, which failed, he observed that ABSTRACT: The effects of snail size and diet on encystment of Echi- nostoma caproni cercariae in juvenile Helisoma trivolvis (Colorado strain) snails were studied. Encystment in neonatal (<1-mm shell di- ameter) and juvenile (2- to 3-mm shell diameter) snails was compared 24 hr postinfection (PI) after individual exposure of snails of each size to 1, 5, 10, 25, or 50 cercariae. Significantly more cysts were recovered from juvenile snails exposed to 10, 25, or 50 cercariae than from neon- atals with comparable exposure. The maximum number of cysts recov- ered from juveniles exposed to 50 cercariae was 42, compared with a maximum of 15 cysts in neonatals comparably exposed. Size of H. trivolvis was a major factor in determining cyst burden in this planorbid. A diet of either Romaine lettuce leaf or hen's egg yolk did not have a significant effect on the number of cysts recovered at 24 hr PI from juvenile snails exposed to 25 or 75 cercariae. Survival of infected versus uninfected neonatals was also examined for 7 days. Neonatals exposed ABSTRACT: The effects of snail size and diet on encystment of Echi- nostoma caproni cercariae in juvenile Helisoma trivolvis (Colorado strain) snails were studied. Encystment in neonatal (<1-mm shell di- ameter) and juvenile (2- to 3-mm shell diameter) snails was compared 24 hr postinfection (PI) after individual exposure of snails of each size