IV-Trifluoroacetylation

Unlike CO, it is possible to polymerize isocyanides (R—N=C), isoelectronic analogs to CO. When R is a bulky group, such as tert-Bu, the polymer forms a stable helical structure. Asymmetric catalytic polymerization has been reported for t-Bu-NC using [Ni(T 3-allyl)(iV-trifluoroacetyl-proline)]2 providing (M)-helical polymer with 69% ee. The more stable helical polymer was prepared from 1,2-diisocya-nobenzene derivative initiated by a chiral Pd complex. (See Scheme 4.19.)... 

There are numerous other syntheses of indoles, and a modern example is the Wender synthesis. Here a 2-bromo-iV-(trifluoroacetyl)aniline in THF is deprotonated by butyllithium and then, in the same pot, reacted with fert-butyllithium to effect halogen-metal exchange to give the dilithiated derivative. To this intermediate is added an a-bromo ketone. A carbon-carbon bond is established first between the reactants, and then cyclization occurs to form a hydroxyindoline. Finally, dehydration generates the indole (Scheme 7.16). 

The conversion of aryl hydrazones to indoles requires elevated temperatures and the addition of Br msted or Lewis acids. For example a milder conversion when iV-trifluoroacetyl enehydrazines are used as substrates. 

A simple, divergent, asymmetric synthesis of the four stereomers of the 3-amino-2,3,6-trideoxy-L-hexose family has been proposed by Dai and co-workers [523] which is based on the Katsuki-Sharpless asymmetric epoxidation of allylic alcohols ( )-408. iV-Trifluoroacetyl-L-daunosamine, A-trifluoro acetyl-L-acosamine, A-benzoyl-D-acosamine, and A-benzoyl-D-nitrosamine have been derived from methyl sorbate via the methyl 4,5-epoxy-( )-hex-2-enoates obtained via a chemoenzymatic method [524]. Application of the Katsuki-Sharpless enantioselective epoxidation to racemic mono-O-benzylated divinylglycol has allowed us to prepare enantiomerically pure L-lyxo and D-/yro-pentoses and analogs [525,526,527, 528],... 

Originally, the iV-trifluoroacetyl (TFAc) derivative of sialic acid was introduced by Bovins and co-workers as a 2-bromide glycosyl donor, which was reacted with benzyl alcohol in the presence of sym-collidine to give a 1/2 mixture of a- and -glycosides in 30% yield [16]. In our laboratory, the 2-phenylsulfenyl derivative of A-TFAc sialic acid has been used for the synthesis of de-A-acetyl-6-sulfo-sialyl Lewis X [97]. However, Boons and co-workers were again first to describe the high potential of the A-TFAc sialyl donor [98]. 

Funtumine Hydroehlorido iV-Aeetyl derivative iV-Trifluoroacetyl derivative Oxime Hydrazone... 

The dye-labelled analogue of dideoxyadenosine triphosphate, (111) has been synthesised and shown to terminate the syntheses of DNA when catalysed by terminal transferases and DNA polymerases, thus allowing DNA detection by time-resolved fluorescence. Treatment of 5 -0-TBDMS-2, 3 -dideoxyadeno-sine with phenoxycarbonyltetrazole followed by iV-trifluoroacetyl-1,6-diamino-hexane yielded the 6-A-carbamoyl derivative, which was then deprotected, phosphorylated and finally dye-labelled at the aliphatic amino group with the fluorescent dye JA242. Two series of modified AZT polyphosphate metabolites (112) and (113) have been synthesised in order to raise specific antibodies for the development of highly sensitive titration kits for the intracellular metabo-... 

Conversions of the amino acids to methyl-a-hydroxy esters (L8, Wl) and methyl a-chloro esters (M5) have been described, and Bier and Teitelbaum (B13) have chromatographed the volatile amines produced by decarboxylation of amino acids. More recently, attention has been focused on the use of the AT-acylated esters of amino acids, e.g., n-amyl JV-aoetyl (J7), n-butyl iV-trifluoroacetyl (Z3), w-propyl iV-acetyl (G6), n-amyl A -trifluoroacetyl (B14), and methyl AT-trifluoroacetyl (C13, HI). Silyl derivatives have also been prepared (R5). 

LI. Lamkin, W. M., and Gehrke, C. W., Quantitative gas chromatography of amino acids. Preparation of n-butyl IV-trifluoroacetyl esters. And. Chem. 37, 383-389... 

Curphey and Daniel (1978) found the catalytic effect of this acid by serendipity. They observed that crude samples of 2.26 reacted with aqueous LiN02 much more rapidly than the recrystallized samples. TLC tests indicated iV-(trifluoroacetyl)serine as a likely catalytic impurity, and chloroacetic acid was selected as an acid of similar strength. Neither acetic nor hydrochloric acid was as effective. The authors chose LiN02 rather than NaN02, because inorganic Li salts are soluble in the ethanol used for purification of azaserine (Curphey, 1989). 

Pleasance, S., et al.. Analysis of domoic acid and related compounds by mass spectrometry and gas chromatography/mass spectrometry as iV-trifluoroacetyl-O-silyl derivatives, Biomed. Environ. Mass Spectrom., 19, 420, 1990. 

At about the same time, in 1963, it was reported that simple iV-acetyl-peptides (Heyns and Griitzmacher [29]) or iV-trifluoroacetyl peptide esters (F. Weygand et al. [30]) are cleaved under electron impact at the peptide bonds, giving rise mainly to ions corresponding to N-terminal parts of the chain. If such fission occurs at each peptide bond, a series of ions are formed all having the same N-acyl group. This is equal to a stepwise degradation of the chain from its carboxyl end (Fig. 13). 

The enantioseparation of arylpropionic non-steroidal anti-inflammatory drug methyl esters was performed with a stationary phase containing methylated and silylated-(S-CD derivatives. The separation of salsolinol, levetiracetam, fluoxetine, norfluoxetine, ephedrine, methamphetamine, ephedrine type alkaloids, per-fluorodiether, iV-trifluoroacetyl-O-alkyl nipecotic ester, camphor, and 7-butyrolactone derivatives using different native CDs and CD derivatives were also reported. 

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