Schemes compound labels

In order to obtain a compound labeled with a radioactive isotope for studies about the pancreas, p-2- and /i-3-sclenienyl alanine were prepared. Initially the synthetic route shown in Scheme 14, which allowed insertion of radioactive selenium as late in the synthesis as possible, was designed for the ji-2 isomer (116).149... 

Compounds labeled with multiple isotopes of the same atom provide the opportunity to observe virtual isomerization reactions that go undetected in conventional studies.There have been relatively few modern studies of these virtual isomerization reactions," " because the reactions themselves are not common and because of difficulties in drawing general conclusions from the observation of the scrambling of isotopic label during solvolysis (Scheme 8). 

Compound labels, In addition to being concise, focus attention on Important features of a reaction. They allow authors to communicate the versatility and generality of a reaction, mechanism, or scheme efficiently. (See appendix A for more details.)... 

Find out if your set of rules for schemes (generated as part of exercise 5.9) applies to schemes in other articles. Check three articles in The Journal of Organic Chemistry or Organic Letters to see if your rules hold true. In these articles, how do the authors use compound labels and accompanying text to walk the readers through the schemes ... 

Compound labels are common in abstracts. They should follow the numbering scheme used in the main text. (See chapter 4 and appendix A.)... 

Like other abbreviations, compound labels must be defined before they are used alone. In the text, the label is defined by placing it immediately after the fully named compound, usually without parentheses. (Some authors use parentheses, especially for compound labels in subheadings.) Compound labels may also be defined in graphical illustrations of the compound (e.g., equations, tables, figures, schemes). Once defined, the label may be used alone, without parentheses. Consider these examples ... 

Scheme 20. The gas-phase reactions of CoO+ with n-butane. Note that the compound labeled A is a butadiene complex of Co+.

Scheme 21. The gas-phrase reactions of CoO+ with 2-methylpropane (iso-butane). Note that the compound labeled A is a 2-methyl-l-propene (iso-butylene) complex of Co , while the compound labeled B is a trimethylenemethane complex of Co. ...

Both title compounds labelled with [18F], 327 and 328, have been prepared317 according to the reaction scheme outlined in equation 141. 

Scheme 2.2.3. Metabolic pathway of mesosulfuron-methyl in soil under aerobic and anaerobic conditions (compounds labeled in bold were detected at >10% of the applied radioactivity).

Chalcogen incorporation was monitored in the syntheses in Scheme 5.10 compound labels 40-44 in this scheme refer to general cluster core configurations without specific reference to terminal ligands. All reactions involved heterometallic clusters prepared from the facially chelated mononuclear molybdenum or tungsten trisulfide species 38 and 39, and from the previously described MoFe3S4 cubane 12-Mo site-specific... 

Hydrazino compounds can react with one or two equivalents of arenediazonium ions. In reactions of arylhydrazines without substituents at the P-nitrogen in mineral acid media the initial product, the 1,4-diaryltetraz-1-ene (6.24), disproportionates rapidly into aryl azide and amine (Scheme 6-17). As shown by 15N labeling experiments (Clusius and Craubner, 1955), equal amounts of all the products shown in Scheme 6-17 are obtained. In acetate buffer the reaction is regiospecifically different. The diazonium ion attacks the a-, not the P-nitrogen, and a 1,3-diaryltetraz-l-ene is formed (6.25). 

The thiazolecarboxylic acid structure (40) was also guessed in a similar way, from tracer experiments. The unknown compound was converted into the thiamine thiazole by heating at 100°C and pH 2. On paper electrophoresis, it migrated as an anion at pH 4. Tracer experiments indicated that it incorporated C-l and C-2 of L-tyrosine, and the sulfur of sulfate. The synthetic acid was prepared by carboxylation of the lithium derivative of the thiamine thiazole, and the derivatives shown in Scheme 19 were obtained by conventional methods. Again, the radioactivity of the unknown, labeled with 35S could not be separated from structure 40, added as carrier, and the molar radioactivity remained constant through several recrystallizations and the derivatizations of Scheme 17. 

A few data exist on the oxidation by ferricyanide. This is simple second-order (in oxidant and neutral hydrazine), and leads to quantitative production of nitrogen in accordance with scheme (71)-(74) with A 4 k and A i. No scrambling occurs during oxidation of N-labelled N2H4 indicating that all N2 is formed via di-imine" Di-imine so prepared is capable of hydrogenating added unsaturated compounds, for example, phenylpropiolic acid gives m-cinnamic acid" " . 

Scheme 2, A summary of Kriigefs in vivo experiments on the incorporation o] radiolabeled carbons into rat liver RNA upon the administration of the compound shown. The position of A indicates the labeled carbon (see text for references).

Hydroxy or hydroxymethyl groups attached to quinolizine substrates normally show the expected reactivity. For instance, compound 109 was linked to histamine receptor antagonists by esterification with succinic anhydride followed by amidification with the antihistaminic drug to give the fluorescently labeled stmcture 110 for in vivo studies of receptor binding (Scheme 13) <2003BML1717>. 

The incorporation of a fluorine-18 label can also be achieved by standard aliphatic nucleophilic substitution chemistry, as exemplified in Scheme 6.171. Here, the widely used reagent [18F]-/f-fluoroethyl tosylate was utilized to prepare several important 18F-labeled compounds [323],... 

It is interesting to remark that classical hydrogenation is a method used to prepare deuterium-labeled compounds by aromatic dehalogenation, but the usual reaction conditions suffer from several limitations. A microwave-enhanced catalytic dehalogenation procedure for rapid and specific deuterium labeling of N-4-picolyl-4-halogenobenzamide 68, by use of deuterated formate, [41] was recently reported (Scheme 8.25). 

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