Trifluoroacetate Derivatives Research Articles

Isolation and identification of trans-2- and trans-3-hydroxy-1,8-cineole glucosides from Alpinia galanga.

Three hydroxy-1,8-cineole glucopyranosides, (1R, 2R, 4S)- and (1S, 2S, 4R)-trans-2-hydroxy-1,8-cineole beta-D-glucopyranosides, and (1R, 3S, 4S)-trans-3-hydroxy-1,8-cineole beta-D-glucopyranoside, which are possible precursors of acetoxy-1,8-cineoles as unique aroma components, were isolated from the rhizomes of greater galangal (Alpinia galanga W.). Their structures were analyzed by FAB-MS and NMR spectrometry, and the absolute configulation of each aglycone was determined by using a GC-MS analysis with a capillary column coated with a chiral stationary phase. The composition of the diastereomers of (1R, 2R, 4S)- and (1S, 2S, 4R)-trans-2-hydroxy-1,8-cineole beta-D-glucopyranosides in the rhizomes was determined as 3:7 by a GC-MS analysis after preparing the trifluoroacetate derivatives of the glucosides.

Antioxidative activity in the pericarp and seed of Japanese pepper (Xanthoxylum piperitum DC).

The antioxidative activity of the dried pericarp and seed of Japanese pepper was studied. The ethyl acetate extract from the pericarp and the methanol extract from the seed showed strong antioxidative activity against linoleic acid by the ferric thiocyanate and thiobarbituric acid (TBA) methods. Japanese pepper contained 3.9 and 2.9 mg/100 g of dry weight (dw) of tocopherols in the pericarp and seed, respectively, alpha-Toc in the former constituting 82% of total tocopherol and gamma-Toc in the latter constituting 96%. Arbutin and magnoflorine were isolated as antioxidants and their chemical structures determined by instrumental analyses. The contents of arbutin evaluated as the trifluoroacetate derivative by GC-MS were 35 and 3.0 mg/100 g of dw in the pericarp and seed, respectively. Magnoflorine was present only in the seed, and not in the pericarp. Both arbutin and magnoflorine exhibited antioxidative activity against linoleic acid and radical-scavenging activity against the DPPH radical.

1H-pyrido[3,2-b]indoles. Synthesis and investigation of some their spectroscopic and chemical properties

At boiling in trifluoroacetic acid derivatives of 3-cyanovinyl-3-p-nitrophenylaminoindole are cyclized into the corresponding pyrido[3,2-b]indoles as a results of activation of the CN group. Thermal cyclization of ethyl indolylacrylate occurs with participation of the more reactive ethoxycarbonyl group to give 3-cyanopyrido[3,2-b]indole.

One-pot synthesis of oligomeric aryl-substituted PPV analogs with extended π-conjugation

A conceptually novel approach for a stepwise one-pot synthesis of oligomeric poly(phenylvinylene) (PPV, –[C6H4–CHCH]–) analogs with extended π-conjugation of the type H–[CHC(Ar)–C6H4–C(Ar)CH]n–H (n = 2, 4), from the corresponding dienic monomers (n = 1), has been studied. The oligomerizations were performed in high yields by repeating the sequential preparation of the mercuric trifluoroacetate derivative H–[CHC(Ar)–C6H4–C(Ar)CH]n–HgCO2CF3 (n = 1, 2) and its coupling in the presence of PdCl2. The feasibility of this approach was demonstrated by a one-pot preparation of several tetramers, directly from the corresponding monomers.

ChemInform Abstract: Mechanism of Ester Hydrolysis: Trifluoroacetate Derivatives.

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On the Mechanism of Ester Hydrolysis: Trifluoroacetate Derivatives

The hydrolysis rate of trifluoacetates of ArX (X = p-CH3, H, p-F, p-Cl, and m-Cl) was measured as function of pH and buffer concentration. All the reactions were catalyzed by the buffer bases, and the Bronsted plot showed a small upward curvature. The kinetic isotope effect is ca. 2.5−2.3 for the reactions of water. The Hammett plots as well as the plots of log kB vs pKlg are linear. The slopes of these plots are remarkably similar to those corresponding to the hydrolysis of aryl acetates and aryl formates. From these results, we conclude that the reaction corresponds to general base-catalyzed addition of water and break of the leaving group with no intermediate with finite lifetime despite the fact that the trifluoromethyl group stabilized the intermediate considerably.

A Novel Solid-Phase Synthesis of Carboxypyrrolinones

A solid-phase organic synthesis method has been developed for the preparation of 3-carboxypyrrolinones 9. Treatment of polymer-bound malonic acid with amino alcohols afforded the malonamide resin products 6. Benzyl and alkyl amino alcohols were prepared in solution via a two-step procedure without purification and were coupled to the resin directly using a resin capture strategy. Polymer loadings and product conversions were determined by direct cleavage of resin-bound materials and analysis by 1H NMR spectroscopy with an internal standard. Treatment of the polymer-bound malonamides with TFA released the malonamic acids, 10, which underwent further reaction to afford the trifluoroacetate derivatives 11. Secondary amides underwent an additional cyclization to afford oxazoles 12. The malonamide resins 6 can be oxidized to the corresponding ketones 7 by treatment with CrO2(O-t-Bu)2, which can in turn be cyclized in the presence of LDA or LHMDS to afford the carboxypyrrolinones 8. TFA treatment releases the free carboxypyrrolinones, 9, in 43−80% overall yield.

Novel Cations and Molecules from Phosphaalkynes, 1H-Phosphirenes and from Tetraphosphacubane

Generation and trapping (counter ion) of the phosphavinyl cation (the P-analog of vinyl cation) by low temperature protonation of kinetically stable phosphaalkynes in super acid media led to the formation of the corresponding phosphaalkenes without direct observation of a long-lived cation. Reactions of RCP (R = tBu, 1-Ad) with “PhSeF” and with PhSeCl resulted in bis-phenylselenenylation and chlorophenylselenenylation respectively, forming novel Se-containing phosphaalkenes. Ionization of 1-H-triflato-phosphirene with B(OTf) 3 /SO2 led to the direct observation of a persistent phosphirenylium cation. The (CO)5 W-complexed phosphirenylium cation was subsequently generated from the (CO)5 W-complexed triflate and trifluoroacetate derivatives. Progress in P-functionalization of tetraphosphacubane by reactions with potent electrophiles (i.e. MeOTf, EtOTf“PhCH2OTf”, TMSCH2OTf), alkynyl-iodonium triflates and with protic superacids are briefly summarized.

Increased total 7 alpha-hydroxy-dehydroepiandrosterone in serum of patients with Alzheimer's disease.

Evidence has indicated that circulating adrenal steroid quantitites were significantly changed in patients with Alzheimer's disease (AD). Aside of 3 beta-sulfatation and 3 beta-acylations, levels of dehydroepiandrosterone (DHEA) result from production and metabolic transformation yields. 7 alpha-Hydroxylation of DHEA has been described in humans, and 7 alpha-hydroxy-DHEA may be responsible for the known antiglucocorticoid effects of DHEA. Using a negative ion fragmentometry method with gas chromatography/mass spectrometry on trifluoroacetate derivatives, we measured levels of free 7 alpha-hydroxy-DHEA as well as its sulfated conjugate and its fatty acid esters in serum of 10 female patients with AD and of 8 age-matched healthy control women. Free 7 alpha-hydroxy-DHEA levels in AD and controls were not significantly different (240.2 +/- 37.2 pg/ml and 206.8 +/- 21.6 pg/ml, respectively), but sulfate conjugate levels were significantly increased in AD (p = .01) (262 +/- 28.4 and 145.4 +/- 27.6, respectively) as well as fatty acid esters (p = .041) (65.7 +/- 6.9 and 40.7 +/- 9.2, respectively). These results indicated that the total 7 alpha-hydroxy-DHEA produced was significantly increased in AD (p = .024) and may contribute to the disease-related disturbances of DHEA production and metabolism.

Measurement of dexfenfluramine metabolism in rat liver microsomes by gas chromatography-mass spectrometry.

A specific and useful method was developed for the determination of dexfenfluramine metabolism by microsomal systems utilising GC-MS. The synthesis of two metabolites 1-(3-trifluoromethylphenyl)propan-2-ol ('alcohol') and 1-(3-trifluoromethylphenyl)-1,2-propanediol ('diol') via straightforward routes, were confirmed by MS and NMR spectra. The conditions for extraction from alkalinised microsomal mixtures of the metabolites nordexfenfluramine, 1-(3-trifluoromethylphenyl)propan-2-one ('ketone'), alcohol and diol, their conversion to trifluoroacetate derivatives and analysis by GC-MS-SIM are described. Calibration curves were constructed between 48 and 9662 nM and fitted to quadratic equations (r2>0.999). The method precision was good over low (121 nM) medium (2415 nM) and above medium (9662 nM) concentrations for all metabolites; the within- and day-to-day coefficients of variation ranged between 2.5-12.4% and 6.7-17.5%, respectively. The accuracy, measured as bias, was very good both within- and day-to-day (range: -0.4-12.6%, 0.8-18.9%). For most metabolites, the C.V. for the assay and bias increased at 121 nM. Dexfenfluramine metabolism by rat liver microsomes was investigated using the assay method and showed a concentration dependent increase in nordexfenfluramine and ketone metabolites over the substrate range of 5-200 microM.

Novel Cyclopentadienyl-Free Organolanthanides: The First Examples of Five-Membered Amidolanthanide Heterocycles.

Reactions of LnCl(3) (Ln = Nd, Gd, Yb) and [{Me(2)SiN(R)Li}(2)] (R = t-Bu, Ph) give the chloride-bridged dimers [{{(t-Bu)NSiMe(2)SiMe(2)N(t-Bu)}Ln(&mgr;-Cl)(THF)}(2)] (1, Ln = Nd; 2, Ln = Gd; 3, Ln = Yb) and [{{(Ph)NSiMe(2)SiMe(2)N(Ph)}Ln(&mgr;-Cl)(THF)(2)}(2)] (4, Ln = Nd; 5, Ln = Gd; 6, Ln = Yb) in good yields. Compounds 2 and 5 were structurally characterized by X-ray crystallography: 2, triclinic, P&onemacr;, a = 10.321(2) Å, b = 11.116(2) Å, c = 13.434(3) Å, alpha = 107.57(3) degrees, beta = 111.31(3) degrees, gamma = 90.67(3) degrees, V = 1356.1(5) Å(3), Z = 1, R = 0.0233; 5, monoclinic, P2(1)/n, a = 13.913(13) Å, b = 12.914(9) Å, c = 16.434(14) Å, beta = 105.64(3) degrees, V = 2843(4) Å(3), Z = 2, R = 0.0281. The chloro functions in 1-6 remain reactive, demonstrated by the isolation of the trifluoroacetate derivatives of 1 and 2. Treatment of 1 or 2 with 2 equiv of NaOCOCF(3) gives [{{(t-Bu)NSiMe(2)SiMe(2)N(t-Bu)}Ln(&mgr;-OCOCF(3))(THF)}(2)] (7, Ln = Nd; 8, Ln = Gd). The structure of 8 was determined by a single-crystal X-ray diffraction analysis. Crystal data for 8: triclinic, P&onemacr;, a = 11.045(2) Å, b = 16.120(3) Å, c = 16.949(3) Å, alpha = 66.17(3) degrees, beta = 85.51(3) degrees, gamma = 78.27(3) degrees, V = 2702.9(9) Å(3), Z = 2, R = 0.0311. The structure of 8 shows the trifluoroacetate group adopting a bridging bidentate mode of coordination.

Carbocations in the β-Lactam and β-Thiolactam Series

Solvolyses of mesylate and trifluoroacetate derivatives of 3-aryl-3-hydroxy-substituted β-thiolactams and β-lactams proceeds to give substitution products in a process which exhibits a large solvent effect as well as large substituent effects. A common ion rate suppression as well as largely racemic products from solvolyses of an optically active substrate all point to the involvement of β-lactam derived carbocationic intermediates. Unlike acyclic analogs, these cations are captured by solvent to give simple substitution products with no competing proton loss. Computational studies suggest that proton loss from these β-lactam derived cationic intermediates is an unfavorable process due to antiaromatic character in the potential elimination product. Computational studies also suggest that CS and CO conjugative stabilization of these cations is minimal or non-existent. Substituent effect studies show that the major mode by which these cations derive stabilization is by aryl group charge delocalization. Azide ion in DMSO or DMF reacts with N-methyl-3-mesyloxy-3-phenylazetidine-2-thione via a bimolecular substitution mechanism to give the corresponding 3-azido substitution product, which can be converted to N-methyl-3-amino-3-phenylazetidine-2-thione.

Identification of ephedrines as their carbon disulfide derivatives.

A method for the separation and identification of the diastereoisomers ephedrine and pseudoephedrine and the diastereoisomers norephedrine and norpseudoephedrine is presented. The compounds were derivatised by reaction with carbon disulfide in the presence of alkali. These derivatives and their trifluoroacetic anhydride derivatives were subjected to gas chromatography with nitrogen-selective detection as well as mass-selective detection and high-performance liquid chromatography with ultraviolet detection. The results showed that ephedrine and pseudoephedrine can easily be differentiated by gas chromatographic analyses of their carbon disulfide derivatives. Norephedrine and norpseudoephedrine can be differentiated by the different chromatographic retention times of their carbon disulfide derivatives and by the fact that norephedrine yielded two products and norpseudoephedrine only one product when reacted with carbon disulfide under the same conditions. Trifluoroacetylation of the latter compounds gave a more pronounced differentiation.

Supercritical fluid extraction of diosgenin from tubers of Dioscorea nipponica

Supercritical fluid extraction (SFE) was used to extract diosgenin following acid hydrolysis from Dioscorea nipponica tuber. Diosgenin determinations were carried out using capillary GC of trifluoroacetate derivatives. Highest diosgenin yields were obtained using 3100 p.s.i. (1 p.s.i. = 6894.76 Pa) pressure for 70 min, but > 82% of this yield was extracted by 40 min. Higher recoveries were obtained than by extraction using light petroleum (b.p. 40–60°C) extraction.

End‐group analysis of poly(phenyl glycidyl ether), 1. Hydroxylic groups using 1H and 13C nuclear magnetic resonance

AbstractThe hydroxylic end‐groups in the soluble fraction of poly(phenyl glycidyl ether) (PPGE) obtained with the aluminium isopropoxide (AIP)/ZnCl2 initiator system are studied using nuclear magnetic resonance spectroscopy (NMR). To achieve complete assignment, model compounds are synthesized and their carbamate and trifluoroacetate derivatives obtained from trichloroacetyl isocyanate (TAI) and trifluoroacetic anhydride (TFAA) are prepared. These derivatizating reagents allow primary and secondary alcohols to be distinguished, since upfield or downfield shifts are produced, and at the same time they have the potential of separating overlapping peaks. Several PPGEs with different degrees of regularity are also synthesized using various initiator systems. Thus, it is possible to identify the carbon signals of both final hydroxylic groups and their adjacent units, and the presence of two types of unit linked to secondary hydroxylic end‐groups is demonstrated. Likewise, in the soluble fraction prepared with AIP/ZnCl2 the absence of the irregular units linked to secondary hydroxylic end‐group is demonstrated, so proving the high regularity of this fraction.

2,2,2-Trifluoroethyl aryl selenides: ArSeCH 2CF 3 (Ar=C 6H 5, p-CH 3C 6H 4) and their derivatives ArSe(O)CH 2CF 3 and ArSe(X) 2CH 2CF 3 (X=Cl, Br, OOCCF 3)

The title selenides were prepared in good yield by reacting the appropriate aryl selenolate anions with 2,2,2-trifluoroethyl tosylate in refluxing tetrahydrofuran. These unsymmetrical bivalent selenides can be oxidised to the corresponding compounds of tetravalent selenium, ArSe(X) 2CH 2CF 3 (X = Cl and Br) with elemental chlorine and bromine. The latter, upon basic hydrolysis, gave the selenoxides, ArSe(O)CHCF 3. Selenoxides have also been formed by direct reaction of the selenides with hydrogen peroxide. Upon reaction with trifluoroacetic anhydride, these gave trifluoroacetate derivatives, ArSe(OOCCF 3) 2CH 2CF 3, in quantitative yield. The compounds have been characterized via elemental analysis, infrared spectra, 1H and 19F NMR spectra, and mass spectra.

Investigation into the GC separation of enantiomers on a trifluoroacetylated cyclodextrin. Part II: Effect of derivatization on stereoselectivity towards alcohols

AbstractTwo acyl and three fluoroacyl derivatives of 32 chiral alcohols have been chromatographed on a GC column coated with octakis(2,6‐di‐O‐n‐pentyl‐3‐O‐trifluoroacetyl)‐ γ‐cyclodextrin. Significant differences were observed between the stereoselectivity obtained for the derivatives and that for the underivatized alcohols. Of the derivatives, only the fluoroacylated compounds were separated into enantiomers. Derivatization with fluoroacyl groups reversed the elution order for at least some of the analytes. Stereoselectivity towards simple 2‐ and 3‐hydroxy alkanes and their fluoroacyl derivatives was highest for those alcohols with a four‐carbon chain attached to the stereogenic center. For longer‐chain fluoroacyl derivative groups stereoselectivity was higher for the 2‐ and 3‐hydroxy alkanes. Differences in stereoselectivity towards alcohols with a methyl‐branched alkane chain and their fluoroacyl derivatives was related to the distance between the methyl group and the hydroxyl or fluoroacyl groups. Different degrees of saturation in the carbon chain resulted in differences in stereoselectivity. Thermodynamic data calculated for a number of analytes suggest that the alcohols and trifluoroacetate derivatives are interacting with the stationary phase by similar mechanisms. The stereospecific interaction appears to have a hydrogen bonding or dipole–dipole contribution and some form of steric component, depending upon the shape and/or size of the solute.

Occurrence of Fumonisin in Forage Grass in New Zealand

Fumonisin B(1) (FB(1)) was isolated from samples of forage grass originating in paddocks associated with an idiopathic disease of Canadian wapiti and wapiti-red deer hybrids characterized by "ill thrift" and liver dysfunction. Four of 40 samples contained 1, 3, 6, and 9 ppm (micrograms per gram) of FB(1) and 4, 0.5, 2, and 0.5 ppm, respectively, of the methyl ester of FB(1). Analyses were done by ion spray mass spectrometry and confirmed by both fast atom bombardment (solids probe) and mass spectral analysis by electron impact ionization of the trifluoroacetate derivative of the base hydrolyzed product (pentolamine) of FB(1). This article contains the first report of the presence of fumonisin B(1) in grass.

The mass spectra of 4-aminophenanthrene and its trifluoroacetic anhydride and perflnoropropionic anhydride derivatives

Several aminophenanthrenes have been examined with electron impact mass spectrometry. The trifluoroacetic anhydride (TFAA) and perfluoropropionic anhydride (PFPA) derivatives of 4-aminophenanthrene have been studied with electron impact as well as both positive and negative ion chemical ionization mass spectrometry utilizing methane as a reagent gas. The resulting mass spectra indicate a loss of water from the derivatives and a mechanism is proposed to account for this loss. The spectra also indicate unique fragmentation patterns associated with the position of the substituent, particularly the four position which is in the region of the molecule termed the bay region. Another interesting aspect is the spectral differences observed for the TFAA and PFPA derivatives of 4-aminophenanthrene. The positive ion chemical ionization mass spectrum of the TFAA derivative indicates an ion [M + H - H2O]+; however, the mass spectrum of the PFPA derivative of 4-aminophenanthrene indicates no water loss from the [M + H]+ ion. The negative ion chemical ionization mass spectra of the two derivatives are also very different. The mass spectrum of the TFAA derivative shows an [M - 18]- ion and the PFPA derivative shows successive losses of HF with no apparent loss of water.

Alkenyl- und Ethylkomplexe des Titanocens. Molekülstruktur von [Cp 2Ti(CMeCHMe)] 2μ-O

The acetylene complexes Cp 2Ti(PMe 3)(C 2H 2) ( 1) and Cp 2Ti(C 2Me 2) ( 2) and the ethylene complex Cp 2Ti(C 2H 4) ( 3) react with alcohols ROH (R = Me, Et, Ph) to give the η 1-alkenyl complexes Cp 2Ti(CR′=CHR′)(OR) (R′ = H, Me) and the ethyl complexes Cp 2Ti(Et)(OR). The reaction of 1–3 with water results in the formation of the oxo-bridged dimeric complexes [Cp 2Ti(CR′=CHR′)] 2μ-O and [Cp 2Ti(Et)] 2μ-O. The acids HX (X = Cl, CF 3COO) react with 1 and 2 to give the monomeric η 1-alkenyl compounds Cp 2Ti(CR′=CHR′)(X). The trifluoroacetate derivatives are very unstable and react with water to yield the stable oxo-bridged complex [Cp 2Ti(OOCCF 3)] 2μ-O. The crystal structure of [Cp 2Ti(CMe=CHMe)] 2μ-O is described.