Trifluoroacetyl, tfa

Analytical Properties Baseline and near-baseline separations of racemic mixtures of /V-perfluoroacyl-2-aminoethyl benzenes, trifluoroacetyl (TFA), pentafluoropropionyl (PFP), heptafluorobutyl (HFB)... 

TFA-L-Valine[L-Valine, A-(trifluoroacetyl)-] TFA-Di.-Phenylalanme[DL-Phenylalanine, A -(trifluoroacetyl)-] TFA-L-Phenylalanine[L-Phenylalanine, AT-(trifluoroacetyl)-] TFA-L-Leuoine[L-Leucine, A -(trifluoroacetyl)-]... 

TFA-DL-Alanme[DL-Alanine, A-(trifluoroacetyl)-] TFA-Glycylglyoine[Glycine, A-[A-(trifluoroacetyl)glycyl-]] TFA-ii-Prolyglycine, ethyl ester[Glycine, A-[l-(trifluoroacetyl)-n-prolyl]-, ethyl ester]... 

Trifluoroacetyl (TFA) derivatives, which have been used for gas chromatography of amino acids, have recently been introduced to the carbohydrate field. Vilkas et al. (317) reported the separation of a number of pentoses, hexoses, amino sugars, methyl glycosides, and disaccharides as... 

Common solvent, such as THF, CH Cl, and CH Cl-CH Cl after reaction of the polymers with trifluoroacetylation (TFA)... 

Screening C. 2 ml anabolic steroids, some diuretics, some S-blockers and S-2-agonists - purification - enzymatic hydrolysis - extraction - concentration - TMS, trifluoroacetyl (TFA) derivatization -GC-MS selected ion monitoring (SIM) analysis ... 

The N-trifluoroacetyl (TFA) methyl esters of the glutathione conjugates were prepared by trifluoroacetylation of the isolated glutathione conjugate ( > 40 yg) in 100 yl of trifluoroacetic anhydride for 15 minutes. The mixture was evaporated under a gentle stream of nitrogen and the residue taken up in 0.5 ml anhydrous methanol to which was added 0.2 ml of freshly distilled diazomethane in ether. After a 5 minute reaction period the solvents and excess diazomethane were evaporated under a stream of nitrogen and the residue was dissolved in 10 yl of methanol. Samples of 1, 2 and 5 yl were evaporated in capillary tubes for mass spectral analysis. 

Derivatization steps are necessary if relatively polar compounds containing, e.g., carboxylic, hydroxy, or primary or secondary amino groups are to be determined by GC or GC-MS. The following procedures are typically used for basic compounds acetylation (AG), trifluoroacetylation (TFA), pentafluoropropiony-lation, heptafluorobutyration (HFB), or trimethylsilylation (TMS), or for acidic compounds methylation, extractive methylation, pentafluoropropylation, trimethylsilylation or tert-butyldimethylsilylation. Further details and the pros and cons of derivatization procedures can be found in a review by Segura et al. [38]. 

Trifluoroacetylation (TFA) with bifluoroacetic anhydride in hexane gave single peaks with ergocalciferol and cholecaldferol at column temperatures of 215-220°C, indistinguishable from those obtained with the corresponding pyro and isopyro vitamin D (Table VI) (Fig. 8). However, at lower temperatures (about 200°C), the trifluoroacetate peak develops a shoulder or a distinctly new peak indicative of the formation of thermal isomers described earlier. 

NMR spectroscopy can be used to analyze mixtures of amino acids and peptides (Sievers et al, 1969). Trifluoroacetyl (TFA) derivatives are prepared and the F spectrum recorded. The F chemical shift is sensitive not only to the nature of the amino acid to which it is directly boun4 but also to the nature of the next amino acid. TFA-Gly-Leu-OMe and TFA-Gly-Ala-OMe show differences in F chemical shifts. The first difference in structure between these two peptides is nine bonds removed from the fluorine nucleus. F spectra show two peaks in a mixture of TFA-D-Val-L-Val cyclohexylester and TFA-D-Val-D-Val the technique could prove useful in detecting racemization during peptide synthesis. 

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