Chemical Transformation Methods Research Articles

Two neglected but valuable genetic tools for Escherichia coli and other bacteria: In vivo cosmid packaging and inducible plasmid replication.

In physiology and synthetic biology, it can be advantageous to introduce a gene into a naive bacterial host under conditions in which all cells receive the gene and remain fully functional. This cannot be done by the usual chemical transformation and electroporation methods due to low efficiency and cell death, respectively. However, in vivo packaging of plasmids (called cosmids) that contain the 223 bp cos site of phage λ results in phage particles that contain concatemers of the cosmid that can be transduced into all cells of a culture. An historical shortcoming of in vivo packaging of cosmids was inefficient packaging and contamination of the particles containing cosmid DNA with a great excess of infectious λ phage. Manipulation of the packaging phage and the host has eliminated these shortcomings resulting in particles that contain only cosmid DNA. Plasmids have the drawback that they can be difficult to remove from cells. Plasmids with conditional replication provide a means to "cure" plasmids from cells. The prevalent conditional replication plasmids are temperature-sensitive plasmids, which are cured at high growth temperature. However, inducible replication plasmids are in some cases more useful, especially since this approach has been applied to plasmids having diverse replication and compatibility properties.

Facile Strategy to Output Fluorescein from Nucleic Acid Interactions.

Biomolecular operations, which involve the conversion of molecular signals or interactions into specific functional outputs, are fundamental to the field of biology and serve as the important foundation for the design of diagnostic and therapeutic systems. To maximize their functionalities and broaden their applicability, it is crucial to develop novel outputs and facile chemical transformation methods. With this aim, in this study, we present a straightforward method for converting nucleic acid signals into fluorescein outputs that exhibit a wide range of functionalities. This operation is designed through a DNA-templated reaction based on riboflavin-photocatalyzed oxidation of dihydrofluorescein, which is readily prepared by simple NaBH4 reduction of the fluorescein with no complicated chemical caging steps. The templated photooxidation exhibits high efficiency (kapp = 2.7 × 10-3/s), generating a clear fluorescein output signal distinguishable from a low background, originating from the high stability of the synthesized dihydrofluorescein. This facile and efficient operation allows the nucleic acid-initiated activation of various fluorescein functions, such as fluorescence and artificial oxidase activity, which are applied in the design of novel bioanalytical systems, including fluorescent and colorimetric DNA sensors. The operation presented herein would expand the scope of biomolecular circuit systems for diagnostic and therapeutic applications.

Seco-Sesquiterpenes and acorane-type sesquiterpenes with antiviral activity from the twigs and leaves of Illicium henryi Diels

Chemical investigation of an alcohol extract from the twigs and leaves of Illicium henryi Diels resulted in the isolation of two new acorane-related seco-sesquiterpenes (1 and 3), two new acorane-related seco-norsesquiterpenes (2 and 4), one new 2-epi-cedrane sesquiterpene (5), eight new acorane-type sesquiterpenes (6–13), and a known major constituent of acorenone B (14). Their structures were established by interpreting extensive spectroscopic data, including HRESIMS, NMR (1H and 13C NMR, 1H-1H COSY, HSQC, and HMBC), and NOE difference spectra analysis. The absolute configurations of 1, 2, 4–7, 9, 10, and 14 were determined by X-ray crystallography, while chemical transformation methods were performed with compound 14 as the starting material to elegantly solve the absolute configuration issue of compounds 8 and 11–13. Notably, 1 and 2 are seco-sesquiterpenes that are related to acorane and possess an unusual ketal-linked hemiacetal in a 6,8-dioxabicyclo[3.2.1]octan-7-ol scaffold ring system. Plausible biosynthetic pathways for compounds 1–14, which were derived from the acorane skeleton, were proposed. All the isolated compounds (1–14) were evaluated for their antiviral and cytotoxic activities.

Chemical transformation of Jojoba oil and Soybean oil and study of their uses as bio-lubricants

Bio-based lubricants have traditionally piqued interest as a supplement to mineral oil-based lubricants in response to rising environmental pollution concerns and declining petroleum assets. This paper discussed the synthesis of bio-lubricants from vegetable oils such as soybean (SOY), and jojoba (JOJ) oil using chemical transformation methods such as epoxidation of the carbon-carbon double bonds in the structure of their already high resistance to air oxidation using a combined catalyst of Amberlite IR 120 and peroxide catalyst with high yield (80 %), followed by transesterification, ring-opening of vegetable oils, and finally acetylation of the hydroxylated obtained products. The rheological and tribological characteristics of the compounds produced were examined to validate their suitability as bio-lubricants using FT-IR, 1H NMR, and TGA techniques. These results demonstrate the possibility of an environmentally sustainable method for producing bio-lubricants.

Amines as Catalysts: Dynamic Features and Kinetic Control of Catalytic Asymmetric Chemical Transformations to Form C-C Bonds and Complex Molecules.

Carbonyl transformations involving enolates and/or enamines have been used for various types of bond-forming reactions. In this account, catalysts and catalyst systems that have amino acids or primary, secondary, and/or tertiary amines as key catalytic functional groups that we have developed to accelerate chemical transformations, including regio-, diastereo- and enantioselective reactions, are discussed. Our chemical transformation strategies and methods that use amine derivatives as catalysts are also discussed. As amines can have different functions depending on protonation and on the species formed during the catalysis (such as enamines and iminium ions), dynamics and kinetic controls are the keys for understanding the catalysis. Further, strategies that harness dynamic steps and kinetic control in amine-catalyzed reactions have enabled the synthesis of complex molecules in stereocontrolled manners. Understanding the dynamic features and the kinetic controls of the catalysis will further the design of the catalysts and the development of chemical transformation strategies and methods.

Semisynthesis of a Homogeneous Glycoprotein Using Chemical Transformation of Peptides to Thioester Surrogates.

Semisynthesis using recombinant polypeptides as building blocks is a powerful approach for the preparation of proteins with a variety of modifications such as glycosylation. The activation of the C terminus of recombinant peptides is a key step for coupling peptide building blocks and preparing a full-length polypeptide of a target protein. This article reports two chemical approaches for transformation of the C terminus of recombinant polypeptides to thioester surrogates. The first approach relies on efficient substitution of the C-terminal Cys residue with bis(2-sulfanylethyl)amine (SEA) to yield peptide-thioester surrogates. The second approach employs a native tripeptide, cysteinyl-glycyl-cysteine (CGC), to yield peptide-thioesters via a process mediated by a thioester surrogate. Both chemical transformation methods employ native peptide sequences and were thereby successfully applied to recombinant polypeptides. As a consequence, we succeeded in the semisynthesis of a glycosylated form of inducible T cell costimulator (ICOS) for the first time.

Isolation, structural elucidation and antiplasmodial activity of fucosterol compound from brown seaweed, Sargassum linearifolium against malarial parasite Plasmodium falciparum

The brown seaweed, Sargassum linearifolium (Turner) C. Agardh, 1820 is commonly available along the south-east coast of India. Its compound fucosterol was isolated and confirmed through spectral characterisation and chemical transformation methods. The antiplasmodial effect of the isolated fucosterol was investigated against the 3D7 chloroquine sensitive Plasmodium falciparum strain, parasitaemia percentage was determined at 48 h and morphological change was studied through microscopic examination after Giemsa staining. A perceptible antiplasmodial effect was produced by fucosterol compound against the P. falciparum and positive control, chloroquine with the IC50 values (μg/mL) of 7.48 and 12.81, respectively. Fucosterol showed higher antiplasmodial activity as compared to chloroquine. It is inferred that both the fucosterol and chloroquine could have inhibited the schizont stage of the parasite during the intra-erythrocyte asexual development. The findings underline the usefulness of the seaweed-based fucosterol and further studies are warranted.

Eleven new highly oxygenated triterpenoids from the leaves and stems of Schisandra chinensis

Eleven new triterpenoids, schinchinenins A–H (1–8) and schinchinenlactones A–C (9–11) together with three known triterpenoids, henrischinins A–C (12–14), were isolated from the leaves and stems of Schisandra chinensis by bioassay-guided fractionation. Schinchinenin A (1) is the first example of a highly oxygenated triterpenoid characterized by a 5/5/7/6/5-fused pentacyclic ring and a 3-one-2-oxabicyclo[3.2.1]-octane moiety. Schinchinenins E and F (5 and 6) are highly oxygenated triterpenoids that contain a hydroperoxyl moiety, which is rare in compounds from the Schisandra genus. The structures and stereochemistry of 1–11 were elucidated using spectroscopic analysis, single-crystal X-ray diffraction, computational optical rotation, chemical transformation, and CD exciton chirality methods. The activities of compounds 1, 2, 7, and 12–14 against HSV-2 and adenovirus were evaluated for the first time, and of these compounds, 13 was the most active inhibitor of HSV-2, with a selectivity index value as high as 29.95.

Valorisation of Glycerol as Renewable Feedstock: Comparison of the Exploration of Chemical Transformation Methods Aided by High Throughput Experimentation

Renewable feedstocks have been in the spotlight of intensive research activities over the past 10 years. Glycerol is one of the feedstock molecules which has been the target of numerous research efforts, for a number of reasons. First of all glycerol is currently readily available due to the fact that it is a couple product of the first generation biodiesel production. Secondly glycerol can be taken as a representative model substrate to explore the options of selective conversion of sugar alcohols to products of value. In our paper we discuss potential routes for the valorisation of glycerol which lead to intermediates already established within the petrochemical value chain and illustrate what impact high throughput experimentation may have as a success factor on research and development for this field. As illustrative examples we have chosen the oxidative transformation of glycerol to acrolein and acrylic acid and the carbonylation of glycerol to C4-acids.

Chemical Constituents and Biological Studies of the Leaves of Grevillea robusta

Three new compounds: Graviquinone (1), cis-3-hydroxy-5-pentadecylcyclohexanone (2), and methyl 5-ethoxy-2-hydroxycinnamate (3), and thirty-eight known compounds were isolated and identified from the leaves of Grevillea robusta. The structures of these compounds were determined by spectroscopic and chemical transformation methods. Graviquinone (1) showed the strongest cytotoxicity against MCF-7, NCI-H460, and SF-268 cell lines. Methyl 2,5-dihydroxycinnamate (4), graviphane (13), and dehydrograviphane (14) exhibited very potent DPPH scavenging activity compared with α-tocopherol. Methyl 2,5-dihydroxycinnamate (4) and bis-norstriatol (17) demonstrated strong inhibition of L-DOPA oxidation by mushroom tyrosinase compared with kojic acid.

3‐Phenoxychromones: Natural Distribution, Synthetic and Modification Methods, Biological Properties

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3-Phenoxychromones: Natural distribution, synthetic and modification methods, biological properties

The literature on the natural distribution, synthetic and chemical transformation methods, and pharmacological properties of 3-phenoxychromones were reviewed.

Identification of Nematicidal Fatty Acids and Triglycerides from Seeds of Jubaea chilensis by GC-EI-MS and Chemical Transformation Methods

Nematicidal bioassay-guided fractionation of the n-hexane extract of the seeds of Jubaea chilensis led to the identification of eight known fatty acids and a mixture of triglycerides, reported for the first time for this species. In addition, their corresponding methyl esters were identified to be artifacts generated during the extraction and isolation procedures by using GC-EI-MS and chemical transformation methods. The fatty acid composition of the triglycerides was analyzed by GC-EI-MS and chemical transformation techniques. Among the 17 compounds, only lauric acid and myristic acid exhibited significant inhibitory effects on the movement of Caenorhabditis elegans with minimum inhibitory concentrations (MIC) of 75 microg/ml.

Constituents of Vittaria anguste-elongata and Their Biological Activities

Twelve new compounds, vittarin-A (1), -B (2), -C (3), -D (4), -E (5), -F (6), 3-O-acetylniduloic acid (7), ethyl 3-O-acetylniduloate (8), methyl 4-O-coumaroylquinate (9), vittarilide-A (10), and -B (11), and vittariflavone (12), as well as 20 known compounds have been isolated from the whole plant of Vittaria anguste-elongata. The structures of these compounds were determined by spectroscopic and chemical transformation methods. 5,7-Dihydroxy-3',4',5'-trimethoxyflavone (18) displayed moderate cytotoxicity against human lung carcinoma and central nervous system carcinoma cell lines with inhibition of 89 and 61% at a concentration of 58 microM, respectively. Vittarilide-A (10) and -B (11) and ethyl 4-O-caffeoylquinate (14) exhibited moderate DPPH radical scavenging activity with IC50 values of 91, 290, and 234 microM, respectively.

Constituents from the Stems of Hibiscus taiwanensis.

AbstractFor Abstract see ChemInform Abstract in Full Text.

New Neolignans from Spiraea formosana

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A Novel Phenylpropenoyl Sulfonic Acid and a New Chlorophyll from the Leaves of Petasites formosanus Kitamura.

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Constituents from the Stems of Hibiscus taiwanensis

Five new compounds, hibicuslide A (1), hibicuslide B (2), hibicuslide C (3), hibicutaiwanin (4), hibicusin (5), and fifty-one known compounds have been isolated from the stems of Hibiscus taiwanensis. The structures of these compounds were determined by spectroscopic and chemical transformation methods. Among them, mansonone H (19) and uncarinic acid A (30) inhibited HIV replication in H9 lymphocyte cells. The 9,9'-O-feruloyl-(-)-secoisolaricinresinol (12), myriceric acid C (29), and uncarinic acid A (30) showed cytotoxic activity against human lung carcinoma and breast carcinoma.

Constituents of Quinchamalium majus with Potential Antitubercular Activity

Antitubercular bioassay-guided fractionation of the dichloromethane extracts of the above-ground biomass and roots of Quinchamalium majus led to the identification of six known constituents, betulinic acid (1), daucosterol (2), 5,7-dihydroxyflavone (3), oleanolic acid (4), (-)-2S-pinocembrin (5), and ursolic acid (6), for the first time in this species. Their chemical structures were determined on the basis of spectroscopic evidence and chemical transformation methods. All of these compounds along with additional 11 analogues were evaluated for their antitubercular potential against Mycobacterium tuberculosis in a microplate alamar blue assay, and the primary structure-activity relationships (SARs) for 4 and 6 were discussed. In addition, all the isolates were tested for cytotoxicity against African green monkey Vero cells in order to evaluate for their selectivity potential.

Constituents of Senecio chionophilus with potential antitubercular activity.

Two new sesquiterpenoids, (1S,4S,5R,10R)-1-hydroxy-6-isobutyryloxy-10H-9-oxofuranoeremophilane (1) and 1alpha-hydroxy-6beta-(2xi-methylbutyryloxy)-10alphaH-9-oxofuranoeremophilane (2), along with 21 known constituents, were isolated from the n-hexane and dichloromethane extracts of the above-ground biomass and roots of Senecio chionophilus. The structures of 1 and 2 were elucidated on the basis of spectroscopic evidence and chemical transformation methods. The absolute configuration of 1 was determined by Mosher ester methodology. All of the isolates were evaluated for their antitubercular potential against Mycobacterium tuberculosis in a microplate Alamar Blue assay. Compound 2, 6beta-angeloyloxy-1alpha-hydroxy-10alphaH-9-oxofuranoeremophilane (3), and 4'-hydroxyacetophenone (6) exhibited mild antitubercular activity at minimum inhibitory concentrations of 119, 114, and 121 microg/mL, respectively.