Tagged compounds

AIBN was synthesized using C-labeled reagents and the tagged compound was used to initiate polymerization of methyl methacrylate and styrene. 

Despite the lack of solubility of 15 in fluorocarbon solvents, the huge retention differences between organic compounds (solvent front) and fluorous-tagged compounds (>30 min for the longer tags) translate into simple separations by solid... 

The next step of the biotechnical sequence, yeast fermentation, is of the utmost importance to the chemistry of winemaking as well as to the formation of flavor substances. We have investigated this previously using 14C-tagged compounds (16). Amino acids, for example, enter the yeast fermentation with a quasi biochemical valence with regard to the formation of metabolic side products like alcohols and esters. In that respect, the composition of the fermentation substrate, the grape must, is highly important to the formation of aroma substances by yeasts. 

Sequential chemical tagging methods uses specific compounds (tags) as a code for the individual steps in the synthesis. These tag compounds are sequentially attached in the form of a polymer-like molecule to the same linker or bead as the library compound at each step in the synthesis (Figure 6.10). The amount of tag used at each step must be strictly controlled so that only a very small percentage of the available linker functional groups are occupied by a tag. At the end of the synthesis both the library compound and the tag compound are liberated from the bead. The tag compound must be produced in a sufficient amount to enable it to be decoded to give the history and hence the possible structure of the library compound. 

Molecules labeled with deuterium and/or tritium are useful for fundamental investigations in a variety of chemical fields, particularly spin decoupling in NMR,1 the measurement of coupling constants in ESR,2 mass spectrometry,3-4 and general reaction mechanism studies. Such tagged compounds are also valuable as tracers in biochemical and medical research. 

Available forms As elemental iodine and in a weakly basic solution of sodium iodide in sodium sulfite iodine 131 is also available in tagged compounds such as dithymol diiodide, potassium iodate, diiodo-fluorescein, insulin, ACTH, etc. 

Available forms Phosphate ion in weak hydrochloric acid solution, solid potassium dihydrogen phosphate, P-32 sterile solution, in tagged compounds such as hexaethyltetraphosphate, ribonucleic acid, triphenylphosphine, etc. 

Available forms Solid elemental sulfur, sulfate in weak hydrochloric acid, barium sulfide in barium hydroxide solution, elemental sulfur in benzene solution, in tagged compounds such as carbon disulfide, chlorosulfonic acid, thiourea, sulfanilamide, thiamine, heparin, insulin, Sucaryl, etc. 

Available forms Gas packaged in ampules and in tagged compounds such as water, streptomycin, cortisone, epinephrine, octadecane, stearic acid, etc. 

We have described an efficient general protocol for assaying catalysis using substrates labeled with the fluorescent tag acridone [98]. In this method, reactions are simply analyzed by thin layer chromatography (TLC). Acridone is a highly photoresistant and intensely fluorescent group whose derivatives behave well on TLC. As little as 1 picomole of an acridone-tagged compound is visually detected under illumination with a simple UV lamp, a detection limit that is 10-100 times lower than that for fluorescein or dansyl derivatives. This method is easi-... 

This can be exploited for the extractive separation of fluorous-tagged compounds from other substances. The partition coefficient depends on the size of the fluorous tag and on the organic solvent. The preference for the fluorous phase increases with increasing fluorine content and polarity of the organic phase. As the fluorous solvent, FC-72 (a mixture of CeFu isomers) is often used. At room temperature, it forms biphasic systems with solvents such as toluene, dichloromethane or acetonitrile and with aqueous media. Somewhat surprisingly, diethyl ether and tetrahydrofuran are good solvents for fluorous molecules and are miscible with FC-72 at... 

Eor the separation of perfluoro-tagged compounds from other molecules, fluorous silica gel (FSG also called fluorous reversed-phase silica gel, FRPSG) can be employed. Examples of how perfluoroalkyl chains have been attached to silica gel surfaces are shown in Fig. 5. 

The crude reaction mixture is loaded onto an FSG column. First, the organic components are eluted with polar solvents (acetonitrile/water or methanol/water) while the perfluoro-tagged compounds are retained on the column. The fluorous compounds are then eluted with more fluorophilic solvents (acetonitrile, acetoni-trile/diethyl ether, diethyl ether, FC-72). How strongly a compound is retained depends on the size of the fluorous tag. Untagged molecules are not significantly retained [27]. 

Some syntheses using intermediates with ionic-liquid tags have been reported, but they are not as versatile as solid or fluorous supports. The tagged intermediates and products are often isolated by precipitation and an advantage of ionic liquids is that the affinity and solubility of the tagged compounds can be altered by exchange of the associated anion. 

Figure 14-7 is an example of the course of lubricated wear as followed by surface radioactivity. The progressive accumulation of reaction product on the rubbing track in the presence of a tagged compounded lubricant is shown by the first part of the curve, and the fact that this is the net resultant of simultaneous reaction and wear processes is demonstrated by the shape of the final portion of the curve, Sakurai it at. [11, 12, 13] found such behavior to be characteristic of the following sulfur compounds, singly and in combination sulfur, dibenzyl disulfide, diphenyl disulfide, dodecyl mercaptan and also these sulfur compounds in combination with stearic acid, benzyl chloride, chlorobenzene or hexachloroethane, The qualitative observations are credible enough, but because of experimental difficulties and the complications noted... 

A radioactively labeled (or "tagged") compound is one in which one of the atoms is radioactive. Preparation of labeled compounds may involve lengthy chemical synthesis starting with the radioactive nuclides in elementary form or in a simple compound. 

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