Analysis of Streptomyces avermitilis genes required for avermectin biosynthesis utilizing a novel integration vector.

Ivermectin is the 22,23-dihydro derivative of avermectin B1, a macrocyclic lactone produced by an actinomycete, Streptomyces avermitilis. It is active at extremely low dosage against a wide variety of nematode and arthropod parasites, apparently by virtue of its action on the mediation of neurotransmission by gamma-aminobutyric acid. It is now in commercial use in various countries for the treatment and control of parasites in cattle, horses, and sheep, and is expected to become available for use in swine and dogs. Since studies with the drug in man are in a preliminary stage, it is not yet known whether ivermectin will be useful in human medicine.

https://science.sciencemag.org/content/sci/221/4613/823.full.pdf

Ivermectin: A potent new antiparasitic agent

The use of photochemical transformations is a powerful strategy that allows for the formation of a high degree of molecular complexity from relatively simple building blocks in a single step. A central feature of all light-promoted transformations is the involvement of electronically excited states, generated upon absorption of photons. This produces transient reactive intermediates and significantly alters the reactivity of a chemical compound. The input of energy provided by light thus offers a means to produce strained and unique target compounds that cannot be assembled using thermal protocols. This review aims at highlighting photochemical transformations as a tool for rapidly accessing structurally and stereochemically diverse scaffolds. Synthetic designs based on photochemical transformations have the potential to afford complex polycyclic carbon skeletons with impressive efficiency, which are of high value in total synthesis.

Photochemical Approaches to Complex Chemotypes: Applications in Natural Product Synthesis

Ionic liquids are solvents that consist entirely of ions. These nonvolatile and nonflammable solvents offer interesting opportunities for lanthanide and actinide chemistry. They can replace the organic phase in solvent extraction systems and can be used as nonaqueous electrolytes for electrodeposition of metals. Ionic liquids could find applications in the nuclear fuel cycle. Lanthanide coordination compounds or lanthanide-containing nanoparticles can be obtained via ionothermal or microwave-assisted synthesis in ionic liquids. Lanthanide-doped ionogels are a new type of luminescent hybrid materials. Ionic liquids can serve as solvents for lanthanide-mediated organic reactions, and there are several examples of high reactivity and selectivity.

Lanthanides and Actinides in Ionic Liquids

Separation and preconcentration of uranium from acidic media by extraction chromatography

A new series of neutral bifunctional extractants, alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine oxides, has been prepared and studied as extractants for Am(III) from nitric acid media. Two types of alkyl(phenyl)-N,N-dialkyl CMPO compounds were prepared, one containing N,N-diethyl groups and the other containing N,N-diisobutyl groups. The N,N-diethyl series contained hexyl(phenyl) and 6-methylheptyl(phenyl) derivatives, abbreviated HφDECMPO, and 6-MHφDECMPO, respectively. The N,N-diisobutyl series contained the n-octyl(phenyl), 6-methylheptyl(phenyl), and the 2-ethylhexyl(phenyl) derivatives, abbreviated OφD[IB]CMPO, 6-MHφD[IB]CMPO, and 2-EHφD[IB]CMPO, respectively. Third power extractant dependencies for the extraction of Am(III) from 0.5 and 3 M HNO3 were obtained at low (<0.25 M) concentrations of extractant, but higher power dependencies were obtained above 0.25 M extractant from 3 M HNO3. The HφDECMPO, 6-MHφDECMPO, 6-MHφD[IB]CMPO, and OφD[IB]CMPO [all 0.5 M in diethylbenzene (DEB)] are si...

Selected Alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine Oxides as Extractants for Am(III) from Nitric Acid Media

Benzvalene, the Tricyclic Valence Isomer of Benzene

The extraction behavior of selected transplutonium(III) and lanthanide(III) ions fromnitrate solution was studied using relatively pure dihexyl-N, N-diethyl-carbamoylmethylphosphonate (DHDECMP). The data obtained for Am(III) and Eu(III) using DHDECMP were compared with analogous measurements obtained with dibutyl butylphosphonate (DB[BP]) and in certain cases with dihexyl-N, N-diethylcarbamoylethylphosphonate (DHDECEP). It was found that both the nitrate and extractant concentration dependencies were third power. The Kd 's for Am(III) and for Eu(III) measured from low acid LiNO3 solutions were similar for DHDECMP, DHDECEP, and DB[BP], thus giving no evidence for any significant chelation effect for DHDECMP. Significant differences among DHDECMP, DHDECEP, and DB[BP] are found for the extraction of Am(III) and Eu(III) from 1 to 5 M HNO3. These differences are explained by the ability of DHDECMP (and to a lesser extent, DHDECEP) to buffer itself against HNO3 by protonation of the amide group. The Kd...

Louis Kaplan

Papers

Selected Alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine Oxides as Extractants for Am(III) from Nitric Acid Media

Benzvalene, the Tricyclic Valence Isomer of Benzene

Extraction of selected transplutonium(III) and lanthanide(III) ions by dihexyl-N,N-diethylcarbamoylmethylphosphonate from aqueous nitrate media

Thiation of Nucleosides. IV. The Synthesis of 5-Fluoro-2'-deoxycytidine and Related Compounds1,2

A Photochemical 1,3 Cycloaddition of Olefins to Benzene1