Trifluoroacetylamino acid

The original procedure for the trifluoroacetylation of amino acids used trifluoroacetic anhydride [Acetic acid, trifluoro-, anhydride].4 This reagent, although inexpensive and readily available, has certain disadvantages it is a highly reactive compound and thus has caused undesired reactions such as the cleavage of amide or peptide bonds,5 unsymmetrical anhydrides are formed between the newly formed A-trifluoroacetylamino acids and the by-product trifluoroacetic acid, and excess trifluoroacetic anhydride has caused racemization of asymmetric centers. 

The enantiomeric purities of the (S)-amino acids were checked preparing the corresponding N-trifluoroacetylamino acid methyl esters, which are resolved into enantiomers by gas liquid chromatography on glass capillary... 

Using this (LI) preparation procedure, Stefanovic and Walker (SO) studied the effect of stationary phase-support ratio on the gas-chromatographic separation of trifluoroacetylamino acid butyl esters using ethylene glycol adipate polyester columns. They found that, for certain amino acids, the elution pattern was a function of the amount of liquid phase on the column packing. When 0.5% ethylene glycol adipate was used, sharp well-defined peaks were obtained and all the amino acids listed in Table 6 except cysteine and methionine were completely sepa-... 

Esterification with diazomethane. Treatment with trifluoroacetic anhydride Methyl esters of N-trifluoroacetylamino acids and N-trifluoroacetyldipep tides 20-22... 

The detection of D-amino acids is carried out by enantioselective HPLC or GC of chiral amino acid derivatives. In a frequently applied method, the derivatives are produced in a precolumn by reaction with o-phthalaldehyde and a chiral thiol (cf. 1.2.4.2.4). Alternatively, the amino acids can be transformed into trifluoroacetylamino acid-2-(R,S)-butylesters. Their GC separation is shown in Fig. 1.3. 

Trifluoromethylindole 181 is produced on heating 2-(A -trifluoroacetylamino)benzyl methyl ether in a sealed tube in the presence of triphenylphosphine and a catalytic quantity of /> rra-toluenesulfonic acid (Equation 117) <1996J(P1)1261>. 

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