Solid-phase/solution-phase combinatorial synthesis of neuroimmunophilin ligands

A novel solid-phase/solution-phase strategy for the synthesis of neuroimmunophilin ligands based on GPI 1046 was developed. The synthesis employs a solid-phase esterification strategy followed by a solution-phase pyruvic amide formation to produce multi-milligram quantities of discrete compounds for assay. The protocol was applied to a production library of 880 discrete compounds. A highlight of the strategy is an aqueous extractive purification of the final compounds using a novel liquid/ice extraction system developed for high throughput.     

Efficient synthesis of lactosaminylated core-2 O-glycans

A series of lactosaminylated oligosaccharides found in mucin type O-glycans was synthesized using a generalized block strategy. The synthesis involved the addition of a protected lactosamine donor to a partially protected T-disaccharide derivative. The nonreducing galactose residues of the deblocked oligosaccharide products could be removed by beta-galactosidase from jack bean to produce the corresponding GlcNAc terminated compounds. A series of tri- to hexasaccharides was thus efficiently produced.     

Origin of organic compounds on the primitive earth and in meteorites

The role and relative contributions of different forms of energy to the synthesis of amino acids and other organic compounds on the primitive earth, in the parent bodies or carbonaceous chondrites, and in the solar nebula are examined. A single source of energy or a single process would not account for all the organic compounds synthesized in the solar system. Electric discharges appear to produce amino acids more efficiently than other sources of energy and the composition of the synthesized amino acids is qualitatively similar to those found in the Murchison meteorite. Ultraviolet light is also likely to have played a major role in prebiotic synthesis. Although the energy in the sun's spectrum that can be absorbed by the major constituents of the primitive atmosphere is not large, reactive trace components such as H2S and formaldehyde absorb at longer wavelengths where greater amounts of energy are available and produce amino acids by reactions involving hot hydrogen atoms. The thermal reaction of CO + H2 + NH3 on Fischer-Tropsch catalysts generates intermediates that lead to amino acids and other organic compounds that have been found in meteorites. However, this synthesis appears to be less efficient than electric discharges and to require a special set of reaction conditions. It should be emphasized that after the reactive organic intermediates are generated by the above processes, the subsequent reactions which produce the more complete biochemical compounds are low temperature homogenous reactions occurring in an aqueous environment.     

Screening of natural compounds with hypolipidemic activity]

In the screening programme for natural hypolipidemic compounds 702 strains of soil microorganisms were tested and 25 of them were selected because of their ability to produce compounds inhibiting sterol synthesis in Hep G2 hepatoma cells. The compounds were estimated in the microbiological model with Tolypocladium inflatum 106 as the test microbe. The 2nd stage of the screening resulted in isolation of 13 strains producing compounds with high hypolipidemic activity, analogous to or higher than the activity of lovastatin in the experimental models.     

Potassium channel activators based on the benzopyran substructure: synthesis and activity of the C-8 substituent

The synthesis of a series of methoxy bearing 2,2-dimethyl-2H-1-benzopyrans have been achieved for testing as potassium channel activators. The synthesis involves formation of 6-cyano-8-methoxy-2,2-dimethyl-2H-1-benzopyran from vanillin, epoxidation, then ring opening of the epoxide with nitrogen nucleophiles to produce the new benzopyrans. Biological testing showed a dramatic decrease in activity thus revealing an important site of activity in this class of compounds.     

Myxobacteria isolated in Israel as potential source of new anti-infectives

AIMS: To evaluate the patterns of the production of antimicrobial compounds by Israeli myxobacteria newly isolated from soil samples and barks by a battery of isolation and purification methods. METHODS AND RESULTS: A total of 100 myxobacteria belonging to five of the 12 described genera, were isolated from 48 soil and 45 tree bark samples collected in different areas inside the State of Israel. Four isolation methods based on the peculiar metabolic and cell cycle aspects of myxobacteria, were combined with purification procedures and optimization of cultivation conditions. Ninety-seven strains were fermented and screened for antimicrobial activities. Production of antimicrobial activities was detected in 62 isolates. More than 50% of the collection (54 strains) was able to inhibit Escherichia coli growth. CONCLUSIONS: The results of this study support the idea that myxobacterial strains can be isolated from particular habitats and then cultivated and screened for their capacity to produce secondary metabolites endowed with antibacterial and antifungal activities. Myxovirescin, a typical poliketide myxobacterial antibiotic, has been identified in one Israeli isolate. Althiomycin, a thiazolyl peptide, which inhibits prokaryotic protein synthesis, usually produced by actinomycetes, was detected in three strains selected in this study. SIGNIFICANCE AND IMPACT OF THE STUDY: The results confirm that myxobacteria are prolific producers of a variety of bioactive secondary metabolites including antibacterial and antifungal compounds, being their high frequency of anti-Gram-negative activities particularly appealing for the current anti-infective research. So far their screening has often been hampered because their isolation is time-consuming and are quite difficult to handle and cultivate. In this paper we demonstrate that a proper combination of isolation, purification and cultivation methods allow their pharmaceutical exploitation.     

Unexpected three-component domino synthesis of pyridin-2-ones catalyzed by promiscuous acylase in non-aqueous solvent

The Acylase “Amano” (AA)-catalyzed synthesis of valuable pyridin-2-ones via domino Knoevenagel condensation–Michael addition–intramolecular cyclization–oxidization reaction between aldehyde, cyanoacetamide and ethyl acetoacetate or cyclohexyl acetoacetate was developed in the sense of a one-pot strategy. Various aliphatic, aromatic and hetero-aromatic pyridin-2-ones could also be produced in the reaction. The mechanism was illustrated according to the controlled reaction, pyridin-2-one was formed via the oxidization by oxygen at the final step. This simple and efficient enzymatic domino reaction not only widens its application of AA to organic synthesis, but is also an attractive way for the synthesis of heterocyclic compounds.     

Solid-phase synthesis of second-generation polyproline dendrimers

Second-generation dendrimers have been prepared on solid phase by successive additions of branched polyproline building blocks starting from two different branching units anchored to the solid support. The preparation of Pro-rich building blocks was carried out by stepwise solid-phase synthesis and their iterative addition was performed by a convergent approach, also using solid-phase synthesis. cis-4-Amino-L-proline and imidazolidine-2-carboxylic acid were used as branching units due to their structural resemblance to proline. The optimized strategy allowed the target compounds to be obtained with high purities without the need for purification steps.     

Synthesis,structure, antimycobacterial and anticancer evaluation of new pyrrolo-phenanthroline derivatives

A study concerning design, synthesis, structure and in vitro antimycobacterial and anticancer evaluation of new fused derivatives with pyrrolo[2,1-c][4,7]phenanthroline skeleton is described. The strategy adopted for synthesis involves a [3?+?2] dipolar cycloaddition of several in situ generated 4,7-phenanthrolin-4-ium ylides to different substituted alkynes and alkenes. Stereo- and regiochemistry of cycloaddition reactions were discussed. The structure of the new compounds was proven unambiguously, single-crystal X-ray diffraction studies including. The antimycobacterial and anticancer activity of a selection of new synthesized compounds was evaluated against Mycobacterium tuberculosis H37Rv under aerobic conditions and 60 human tumour cell line panel, respectively. Five of the tested compounds possess a moderate antimycobacterial activity, while two of the compounds have a significant antitumor activity against renal cancer and breast cancer.     

Development and evaluation of a pharmacophore model for inhibitors of aldosterone synthase (CYP11B2)

Recently, we proposed inhibition of aldosterone synthase (CYP11B2) as a novel strategy for the treatment of congestive heart failure and myocardial fibrosis and synthesized a large number of inhibitors. In this work, a pharmacophore model for CYP11B2 inhibitors was developed by superimposition of active and non-active compounds. This model was confirmed by the synthesis of two pyridyl substituted acenaphthene derivatives (A,B). This new class of compounds as well as the pharmacophore could be helpful for the discovery of novel inhibitors.     

Assay for drug discovery: Synthesis and testing of nitrocefin analogues for use as β-lactamase substrates

We report on the synthesis of three nitrocefin analogues and their evaluation as substrates for the detection of β-lactamase activity. These compounds are hydrolyzed by all four Ambler classes of β-lactamases. Kinetic parameters were determined with eight different β-lactamases, including VIM-2, NDM-1, KPC-2, and SPM-1. The compounds do not inhibit the growth of clinically important antibiotic-resistant gram-negative bacteria in vitro. These chromogenic compounds have a distinct absorbance spectrum and turn purple when hydrolyzed by β-lactamases. One of these compounds, UW154, is easier to synthesize from commercial starting materials than nitrocefin and should be significantly less expensive to produce.     

Structure-based virtual screening of hypothetical inhibitors of the enzyme longiborneol synthase—a potential target to reduce <Emphasis Type="Italic">Fusarium</Emphasis> head blight disease

Fusarium head blight (FHB) is one of the most destructive diseases of wheat and other cereals worldwide. During infection, the Fusarium fungi produce mycotoxins that represent a high risk to human and animal health. Developing small-molecule inhibitors to specifically reduce mycotoxin levels would be highly beneficial since current treatments unspecifically target the Fusarium pathogen. Culmorin possesses a well-known important synergistically virulence role among mycotoxins, and longiborneol synthase appears to be a key enzyme for its synthesis, thus making longiborneol synthase a particularly interesting target. This study aims to discover potent and less toxic agrochemicals against FHB. These compounds would hamper culmorin synthesis by inhibiting longiborneol synthase. In order to select starting molecules for further investigation, we have conducted a structure-based virtual screening investigation. A longiborneol synthase structural model is first built using homology modeling, followed by molecular dynamics simulations that provided the required input for a protein–ligand ensemble docking procedure. From this strategy, the three most interesting compounds (hits) were selected among the 25 top-ranked docked compounds from a library of 15,000 drug-like compounds. These putative inhibitors of longiborneol synthase provide a sound starting point for further studies involving molecular modeling coupled to biochemical experiments. This process could eventually lead to the development of novel approaches to reduce mycotoxin contamination in harvested grain.     

Structure-activity relationship study of homoallylamines and related derivatives acting as antifungal agents

The synthesis, in vitro evaluation, and structure-activity relationship studies of homoallylamines and related derivatives acting as antifungal agents are reported. Among them, compounds N-(4-bromophenyl)-N-(2-furylmethyl)amine and N-(4-chlorophenyl)-N-(2-furylmethyl)amine reported here exhibited remarkable antifungal activity against dermatophytes. Theoretical calculations allow us to determine the minimal structural requirements to produce the antifungal response and can provide a guide for the design of compounds with these properties.     

Synthesis and conformational analysis of His-Phe-Arg-Trp-NH2 and analogues with antifungal properties

The synthesis, in vitro evaluation, and conformational study of His-Phe-Arg-Trp-NH2 and related derivatives acting as antifungal agents are reported. Among them, His-Phe-Arg-Trp-NH2 and His-Tyr-Arg-Trp-NH2 exhibited antifungal activity against Cryptococcus neoformans. Antifungal activity of these compounds appears to be closely related to the alpha-MSH effect. A conformational and electronic study allows us to propose a biologically relevant conformation for these tetrapeptides acting as antifungal agents. In addition, these theoretical calculations permit us to determine the minimal structural requirements to produce the antifungal response and may provide a guide for the design of compounds with this biological activity.     

Characterization of CK2 holoenzyme variants with regard to crystallization

A search for strategies was conducted in order to obtain a human protein kinase CK2 preparation which would be suitable for crystallization, despite the fact that the recombinant enzyme is abundant and can be readily purified to homogeneity. This seemingly contradiction is based on the fact that the catalytic subunit moiety of the human CK2 holoenzyme is not stable neither as a free subunit nor in the tetrameric complex. All attempts to prevent degradation failed. Hence, alternative approaches were designed in order to avoid this degradation, which was expected to hamper any crystallization efforts severely. One of the approaches chosen was the production of a chimeric holoenzyme made up from a human regulatory subunit and a catalytic subunit from Z. mays. The plant catalytic subunit, in contrast to the human counterpart is very stable and does not undergo this kind of degradation. The second strategy to tackle the problem of instability was to produce the homologous recombinant human CK2 holoenzyme and then, instead of trying to avoid degradation, attempt to accelerate degradation until all catalytic subunit material was converted to the degraded form, i.e. a 40 kDa polypeptide.     

Synthesis of 5-(pyridinyl and pyridiniumyl)-2'-deoxyuridine nucleosides: reversible electron traps for DNA

The desire to produce reversible electron traps for direct, room temperature studies of excess electron transport in DNA duplexes and hairpins motivated our efforts first to link pyridines to 2'-deoxyuridine (pyridinyl-dU) and then to convert these new conjugates into pyridiniumyl-dU nucleosides. Base sensitivity studies presented here rule out general use of bipyridinediiumyl compounds, but show that pyridiniumyl compounds are suitable for use under the strand cleavage and base deprotection procedures required for automated solid-phase oligonucleotide synthesis. This paper presents the synthesis of four 5'-O-DMT-protected 5-(N-methylpyridiniumyl)-dU conjugates using either ethynyl or ethylenyl linkers to join the pyridiniumyl and dU subunits.     

Microbiology of synthesis gas fermentation for biofuel production

A significant portion of biomass sources like straw and wood is poorly degradable and cannot be converted to biofuels by microorganisms. The gasification of this waste material to produce synthesis gas (or syngas) could offer a solution to this problem, as microorganisms that convert CO and H2) (the essential components of syngas) to multicarbon compounds are available. These are predominantly mesophilic microorganisms that produce short-chain fatty acids and alcohols from CO and H2. Additionally, hydrogen can be produced by carboxydotrophic hydrogenogenic bacteria that convert CO and H2O to H2 and CO2. The production of ethanol through syngas fermentation is already available as a commercial process. The use of thermophilic microorganisms for these processes could offer some advantages; however, to date, few thermophiles are known that grow well on syngas and produce organic compounds. The identification of new isolates that would broaden the product range of syngas fermentations is desirable. Metabolic engineering could be employed to broaden the variety of available products, although genetic tools for such engineering are currently unavailable. Nevertheless, syngas fermenting microorganisms possess advantageous characteristics for biofuel production and hold potential for future engineering efforts.     

Development of a nonauxotrophic L-homoserine hyperproducer in Escherichia coli by systems metabolic engineering

L-Homoserine is a valuable amino acid as a platform chemical in the synthesis of various important compounds. Development of microbial strains for high-level L-homoserine production is an attractive research direction in recent years. Herein, we converted a wild-type Escherichia coli to a non-auxotrophic and plasmid-free hyperproducer of L-homoserine using systematically metabolic engineer strategies. First, an initial strain was obtained through regulating L-homoserine degradation pathway and enhancing synthetic flow. To facilitate L-homoserine production, flux-control genes were tuned by optimizing the copy numbers in chromosome, and transport system was modified to promote L-homoserine efflux. Subsequently, a strategy of cofactors synergistic utilization was proposed and successfully applied to achieve L-homoserine hyperproduction. The final engineered strain could efficiently produce 85.29 g/L L-homoserine, which was the highest production level ever reported from a plasmid-free, antibiotic-free, inducer-free and nonauxotrophic strain. These strategies used here can be considered for developing microbial cell factory of other L-aspartate derivatives.     

Thermodynamics of strecker synthesis in hydrothermal systems

Submarine hydrothermal systems on the early Earth may have been the sites from which life emerged. The potential for Strecker synthesis to produce biomolecules (amino and hydroxy acids) from starting compounds (ketones, aldehydes, HCN and ammonia) in such environments is evaluated quantitatively using thermodynamic data and parameters for the revised Helgeson-Kirkham-Flowers (HKF) equation of state. Although there is an overwhelming thermodynamic drive to form biomolecules by the Strecker synthesis at hydrothermal conditions, the availability and concentration of starting compounds limit the efficiency and productivity of Strecker reactions. Mechanisms for concentrating reactant compounds could help overcome this problem, but other mechanisms for production of biomolecules may have been required to produce the required compounds on the early Earth. Geochemical constraints imposed by hydrothermal systems provide important clues for determining the potential of these and other systems as sites for the emergence of life.     

Isosteric exchange of the acylsulfonamide moiety in Abbott's Bcl-XL protein interaction antagonist

A multi-component reaction strategy was used for the fast and efficient synthesis of amide isosteres of known Bcl-2 inhibitors capable of disrupting protein–protein interactions. Ugi reaction and a subsequent nucleophilic aromatic substitution reaction provide a versatile path to libraries of compounds similar to Abbott’s acylsulfonamides. Modeling arguments are used to explain the inferior activity of the amide as opposed to the sulfonamide series.