Lead compound conversion

Rats are not known to convert triethyl lead to the diethyl form (Bolanowska 1968), but rabbits excrete large amounts of diethyl lead following exposure to alkyl lead (Klaassen and Shoeman 1974). Final conversion to inorganic lead may take place, although trialkyl lead compounds are usually stable in biological tissues. 

Reisinger et al. [21] used the gas chromatographic-atomic absorption spectrometric technique to demonstrate that biomethylation of inorganic lead does not account for the presence of organolead compounds in sediments. Sulphide induced chemical conversion of organic lead(IV) salts into alkyl lead compounds is, however, possible. 

Conversion to tetra-alkyl lead compounds using nBu MgCI then gas chromatography with atomic absorption spectrometric detector Petroleum ether extraction, glc... 

NMR spectra of the compound 13a showed a broad singlet at 4.41 for the clibyl protons, whereas compound 13b showed two multiplets. Conversion of bridgehead carboxylic acids to the corresponding halides using Pb(OAc)4 and iodine in refluxing benzene under illumination is reported. This is considered to be an alternative to Barton s method, because of its simplicity and ease of preparation, but it involves toxic lead compounds. 

Some of these oxidative metabolites are biologically active and may even be more toxic than their parent compounds. Conversion by conjugation reactions is considered to lead to termination of the toxicity of these compounds and excretion of the non-toxic conjugates.58 Oxidative metabolism of a parent compound can lead to different products which may be excreted at different rates, as has been demonstrated for hydroxylated benzo[a]pyrenes.58... 

Abstract Nucleic acids were one of the first biological targets explored with DCC, and research into the application has continued to yield novel and useful structures for sequence- and structure-selective recognition of oligonucleotides. This chapter reviews major developments in DNA- and RNA-targeted DCC, including methods under development for the conversion of DCC-derived lead compounds into probe molecules suitable for studies in vitro and in vivo. Innovative applications of DCC for the discovery of new materials based on nucleic acids and new methods for the modification of nucleic acid structure and function are also discussed. 

Reduction of V, R = Me, in dimethylformamide at mercury leads to conversion of the ketone function to secondary alcohol with essentially no cyclization process observed. However, in the presence of a mediator the course of reaction changes. Addition of N,N-dimethylpyrrolidinium fluoroborate causes formation of the cyclized tertiary alcohol. The pyrrolidinium salt is reduced at —2.7V (vs. SCE) at mercury to yield a complex DMP(Hg5) which is thought to act as a single-electron-transfer mediator [42]. Cyclization also occurs in dimethylformamide at a mercury cathode using a homogeneous redox catalyst such as phenanthrene or 2-methoxybiphenol with a redox potential in the range —2.4 to —2.7 (vs. SCE) [43]. Because during these reactions one electron is delivered to the carbonyl compound in solution by the reduced mediator, cyclization of the reduced carbonyl compound can occur before a second electron donor is encountered. 

The unique feature of these amphibian skin opioid peptides is the sequence between the important aromatic residues. In contrast to the enkephalins and other mammalian opioid peptides that contain the Gly-Gly dipeptide sequence between Tyr and Phe, the amphibian opioid peptides contain a single D-aminoacid (see Fig. 7.41), which apparently arises from a post-translational conversion of the L-amino acid to its d isomer (665). The identification of these unusual opioid peptides expanded our understanding of the structural requirements for interaction with opioid receptors and provided new lead compounds for further modification (see Sections 6.5.1 and... 

Profile Founded in 1996, this privately held company is a developer of leading edge supercomputer-based technology for rapid conversion of novel gene sequence information into protein structural information and drug lead compounds. 

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