Trifluoroacetate derivatives

In these latter compounds, the hypervalent iodine may be associated with oxyanions such as perchlorate, trifluoroacetate, and triflate, as verified by the crystal structure of the trifluoroacetate derivative (41). It seems likely that the mode of binding of... 

Difluoroacetic acid and its derivatives (esters, aldehyde) are excellent reagents for introducing a difluoromethyl group. However, because they are expensive, they are used relatively infrequently. Their reactivity is close to that of trifluoroacetic derivatives. ... 

The reaction of diazomethane with a mixed anhydride is generally complete within 15 minutes. If the peptide contains Tyr the reaction should be worked up immediately to avoid methylation of the Tyr side-chain hydroxy group. In the assessment of purity of peptidyl diazomethyl ketones using HPLC, it should be noted that the peptidyl diazomethyl ketone, R1CHN2, is converted into RlCH COCFj if TFA is used in the HPLC solvent system. The peak seen in HPLC is the trifluoroacetate derivative, sometimes two peaks appear if the reaction is slowJ71... 

Trifluoroacetate derivatives of the Group VI elements are confined to the monosubstituted selenium(VI) fluoride, SeFg(02CCF3) (221), and the hexatrifluoroacetatotellurate(IV) anion, [Te(02CCF3)g] , which has been isolated as the sodium salt (200). 

Attempts to cause iV-arylsulfonation of p-lactams may lead to oligomerization products but a simple change from the usual procedure gives N-arylsulfonyl-2-azetidinones in good yields <97SC3803>. Hydrolysis of N-arylsulfonyl P-lactams in phosphate buffer shows that both a direct hydrolysis and a process involving an unstable acyl phosphate intermediate occur <97JCS(PI)2725>. Solvolysis of the mesylate and trifluoroacetate derivatives of... 

Lissochinotoxin D (273) (amorphous white solid) was isolated from Lissochinum sp. and identified as the trifluoroacetate derivative (274). Compound (273) shows antifungal activity against Candida albicans <94JOC6600>. 

Methyl 2-iodoxybenzoate can be further converted into the diacetate 490 or a similar bis(trifluoroacetate) derivative by treatment with acetic anhydride or trifluoroacetic anhydride, respectively [658]. Single-crystal X-ray diffraction of methyl 2-[(diacetoxy)iodosyl]benzoate 490 revealed a pseudo-benziodoxole stmcture with three relatively weak intramolecular l - O interactions. The esters of 2-iodoxyisophthalic acid (e.g., 491) have been prepared by oxidation of the respective iodoarenes with dimethyldioxirane. X-Ray stmctural analysis of diisopropyl 2-iodoxyisophthalate 491 showed intramolecular I - O interaction with the carbonyl oxygen of only one of the two ester groups, while NMR spectra in solution indicated equivalency of both ester groups [658]. 

Low molecular weight products from the alkaline degradation of cellulose have been identified by g.e.-m.s. of their trifluoroacetate derivatives. Both the residual aqueous phase and the floating oily product were examined and found to contain essentially the same products. These included unsaturated, aliphatic and alicyclic hydrocarbons, aldehydes, ketones, alcohols, and furans. The synthesis of molecules with more than six carbon atoms also occurred. 

The ring-expansion reaction of the trifluoroacetate derivative of piperidine 4, which after hydrolysis gives azepane 5, occurs slowly compared to that of the corresponding pyrrolidine analogs (13SL1529). 

The final steps in the preparation of the catharanthine fragment required that the last remaining protecting group (the t-butyldiphenylsilyl) be removed. This was accomplished with trifluoroacetic acid (TFA). The newly liberated primary alcohol was tosylated (toluensulfonyl chloride in the presence of tetramethylpropylenedi-amine), and the tertiary alcohol was protected as the trifluoroacetate derivative by treatment with trifluoroacetic anhydride in the presence of pyridine. 

The monosaccharide content of glycoproteins containing 6—20% carbohydrates has been determined by high voltage electrophoresis of [ H]-labelled sugar alditols. Methods for the carbohydrate analysis of glycoproteins have been reported. Picomolar quantities of monosaccharides in the form of trifluoroacetate derivatives of methyl glycosides are separated and detected by g.l.c. with an electron capture detector. 

Trifluoroacetate derivatives of hydroxy acids, monoacylglycerols and glycerol ethers are... 

Seventeen alditols, including all possible C -C alditols, have been separated as their per(trifluoroacetate) derivatives in 18 minutes under isothermal conditions, the method being useful for the analysis of aldoses after borohydride reduction." ... 

Hydroxy-acids.—Grignard reagents and alkyl-lithiums condense with chiral a-keto-oxazolines (17) to give a-hydroxy-acids (18) in 30— 90% optical yield, after hydrolysis of the oxazoline group/ Enantiomers of a-hydroxy-acids (as their trifluoroacetate derivatives) have been separated by g.I.c. using a chiral... 

Amphetamines/urine Methanol (0.1% H2SO4) SPE (automatic urine injection onto a Clean Screen CDS cartridge) followed by evaporation of the eluate to dryness. Manual derivatization to trifluoroacetate derivatives in CH2CI2. Calibration graphs (El) are linear from 0.1 to 10 ng/ml RSD = 6%. 23... 

Wilk and co-workers (1965) proposed a degradative procedure for analysing vanilmandelic acid (VMA) to reduce chromatographic difficulties in which VMA is cleaved by sodium periodate, and the resulting vanillin detected by electron capture as its O-trifluoroacetate derivative. Electron-capture detection can also be used in the determination of homovanillic acid as its heptafluorobutyrate derivative (Sjoquist and Anggard, 1972). 

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