Pentafluorophenyl phase

In this case study, two different Cl 8 columns from different manufacturers were used. Alternatively, other stationary phase types could also be used such as a polar embedded phase and a Cl 8 phase. Some systems come also equipped with a six-column switcher and in that case, two different types of polar embedded phases, phenyl phase, pentafluorophenyl phases, two different Cl 8 phases (of different bonding density) and an alternate C8 phase could be used. 

S.P. solid-phase technique L.P. liquid-phase technique OPTcp pentachlorophenyl ester TEEP tetraethyl pyrophosphit OTCp trichlorophenyl ester ONp p-nitrophenyl ester ONSu N-hydroxysuccinimido ester OPFp pentafluorophenyl ester OQu 8-hydroxyquinyl ester OPy 3-hydroxy-pyridyl ester ODnp 2,4-dinitrophenyl ester DCC dicyclohexylcarbodiimide HOBn 3-hydroxy-4-oxo-3,4-dihydro-l,2,3-benzotriazin Opi JV-hy-droxypiperidine EEDQ 2-ethoxy-l-ethoxycarbonyl-l,2-dihydroquinoline Tos p-toluenesulfonyl PTC propanetricarboxylic acid OBu tm-butyl ester Nva norvaline Aha aminohexanoic acid Om ornithine... 

Other applications that utilize different types of reversed-phase columns in both dimensions have been advocated by Carr (Stoll et al., 2006) for metabolomics work in small-molecule separations. These stationary phases include a pentafluorophenyl-propyl stationary phase in the first dimension and a carbon-coated zirconia material stationary phase in the second dimension. A common mistake in 2D method development is to mismatch the solvent system the two solvent systems must be miscible as discussed below. 

Byeon et al. [23] described a fluorimetric method for (z>)-penicillamine using 9-fluorenylmethyl pentafluorophenyl carbonate and acetonitrile. Capsules containing penicillamine were extracted with water and then filtered. The solution was incubated at 70 °C for 40 min with borate buffer solution. After cooling, the mixture was extracted with diethyl ether and the fluorescence of the aqueous phase measured at (excitation = 260 nm, emission = 313 nm). The calibration graph was linear for 0.4-5.0 pM of penicillamine with a coefficient of variation of 0.4%. 

Solution-phase DPV of Au144-C6S dispersed in 10 mM [bis(triphenylpho-sphoranylidene)-ammoniumtetrakis-(pentafluorophenyl)-borate (BTPPATPFB)/ toluene] [acetonitrile] 2 1 revealed well-behaved, equally spaced and symmetric quantized double-layer charging peaks with AE - 0.270 0.010 V. Applying the classical concentric spheres capacitor model (8) reveals an individual cluster capacitance of 0.6 aF [334, 335]. 

Banks and co-workers found that gas-phase pyrolysis of pentafluorophenyl azide yields a diazaheptafulvalene (Scheme 16).50 The formation of the product was viewed as dimerization of the perfluoro analogue of 4b, although it is possible that it could, instead, have been formed by dimerization of the corresponding cyclic ketenimine. 

Otvos et al. (27) adopted the Fmoc-pentafluorophenyl ester methodology and have applied O-deacetylated glycopeptide intermediates (170 and 171) for solid-phase synthesis of glycopeptides. In this way, the A-glycopep-tide (26) H-Gly-L-Lys-L-Ala-L-Tyr-L-Thr-L-Ile-L-Phe-L-... 

M Meldal, B Klaus. Pentafluorophenyl esters for temporary carboxyl group protection in solid phase synthesis of A-linked glycopeptides. Tetrahedron Lett 48, 6987, 1990. 

M Meldal, KJ Jense. Pentafluorophenyl esters for temporary protection of the a-carboxy group in solid phase glycopeptide synthesis. J Chem Soc Chem Commun 483, 1990. 

YH Wang, JC Xu. One-pot liquid-phase synthesis of DSIP and 5-DSIP using fluoren-9-ylmethoxycarbonyl-protected amino acid pentafluorophenyl esters. (3-diethylami-nopropane-2-ol) Synthesis 845, 1990. 

Using the same experimental approach, a family of enantiomerically pure oxonium ions, i.e., O-protonated 1-aryl-l-methoxyethanes (aryl = 4-methylphenyl ((5 )-49) 4-chlorophenyl ((5)-50) 3-(a,a,a-trifluoromethyl)phenyl ((5)-51) 4-(a,a,a-trifluoromethyl)phenyl ((S)-52) 1,2,3,4,5- pentafluorophenyl ((/f)-53)) and 1-phenyl-l-methoxy-2,2,2-trifluoroethane ((l )-54), has been generated in the gas phase by (CH3)2Cl -methylation of the corresponding l-arylethanols. ° Some information on their reaction dynamics was obtained from a detailed kinetic study of their inversion of configuration and dissociation. Figs. 23 and 24 report respectively the Arrhenius plots of and fc iss for all the selected alcohols, together with (/f)-40) of Scheme 23. The relevant linear curves obey the equations reported in Tables 23 and 24, respectively. The corresponding activation parameters were calculated from the transition-state theory. 

Solid-phase techniques can be applied to the N-activated esters.16 In the activated ester method, 4-nitrophenyl, 12 21-27 2,4-dinitrophenyl, 614 28 2,4,5-trichlorophenyl, 29 and penta-fluorophenyl 8 esters can be used, the amide bonds being formed with aminolytic release of the corresponding phenol (Scheme 4). For example, the use of pentafluorophenyl esters in the synthesis of pure azapeptides (named azatides for the first time) proved to be advantageous. 8 ... 

The crude carboxylic acid 55 was dissolved in DMF and cooled to 0°C. Pentafluorophenol (1.1 equiv) and EDC (1.5 equiv) were added and the resulting mixture was stirred at rt for 18 h. The resulting mixture was concentrated under reduced pressure. The residue was dissolved in CHC13 and washed successively with 1M HC1 and H20. The organic phase was dried (MgS04) and concentrated. The resulting pentafluorophenyl ester 56 was used without further purification. 

A better, higher yielding approach for the preparation of templates attached to different peptides employs a combination of solid-phase and solution-phase couplings (Scheme ll).121 A peptide chain is synthesized on a low-loading benzhydrylamine resin and reacted with a bifunctional electrophile such as the bis(pentafluorophenyl) ester 4 (R1 = Pfp) (low resin... 

The discovery in 1971 that allvl pentafluorophenyl ether (22a) rearranges in the vapor phase at 365 C to 4-allyl-2,3.4,5,6-pentafluorocyclohexa-2.5-dienone (24a)19 marked the beginning of intensive and fruitful studies into the Claisen and hetero-Claisen rearrangements of arenes and hetarenes, studies which have been reviewed concisely by the principal investigator of this chemistry. G.M. Brooke.2"... 

The following peptide chains were constructed by solid-phase methodology al, which contained either 3 or 5 Gly-Pro-Hyp repeats on the N-terminus of H-Gly-Pro-Gln-Gly-Ile-Ala-Gly-Gln-Arg-Gly-Val-Val-Gly-Cys(Acm)-Gly-Gly-OH a2, which contained 3 or 5 Gly-Pro-Hyp repeats on the N-terminus of H-Gly-Pro-Gln-Gly-Leu-Leu-Gly-Ala-Hyp-Gly-Ile-Leu-Gly-Cys(Acm)-Cys(StBu)-Gly-Gly-OH and al, which contained either 3 or 5 Gly-Pro-Hyp repeats on the N-terminus of H-Gly-Pro-Gln-Gly-Ile-Ala-Gly-Gln-Arg-Gly-Val-Val-Gly-Leu-Cys(StBu)-Gly-Gly-OH. All three peptides were synthesized using Fmoc chemistry on HMP resin. Couplings were performed with HBTU/HOBt except for Cys residues, which were coupled as pentafluorophenyl esters to minimize racemization. Peptides were cleaved from the resin with H20/TFA (1 19) containing 1% Et3SiH. 

Bouzas et al. [95] developed a quantitation method for the determination of drugs of abuse (opiates, amphetamine and derivatives, cocaine, methadone and metabolites) in serum by using online extraction coupled to LC-MS/MS. The online extraction procedure described consists of an extraction column and an analytical column, which were coupled online. A PPT procedure was performed with zinc sulfate an aliquot of 0.1 M zinc sulfate in methanol was added to the serum sample in a proportion of 2 1 (v/v) to serum. Analytes were extracted by a short pentafluorophenyl silica column and separated on a longer analytical column with the same stationary phase. Recoveries of all analytes were above 80 %. The proposed procedure by Matuszewski et al. [64] was used for the evaluation of matrix effect ME(%)=B/Ax 100, where ME is the matrix effect (suppression or enhancement) and B corresponds to peak areas for standards spiked after extraction into sample extracts and A to peak areas obtained in neat solution standards. Authors compared this method to offline SPE coupled with GC-MS and results showed that LC-MS/... 

Different developed analytical method are discussed in this chapter related to the determination of illicit substances in blood (either whole blood, plasma, or serum), OF, urine, and hair. These methods take into consideration the particular chemical and physical composition of the matrix and applies each time a suitable pretreatment to remove interfering and matrix effect, to maximize recoveries and to achieve a suitable enrichment if necessary. For liquid matrices the applications of the most common techniques are considered from simple PPT to SPE and LLE the results of recent works from literature are reported and new trends as online SPE, pSPE, automated LLE (SLE) or MAE are examined. Several stationary phases have been shown to be suitable for determination of illicit drugs Cl8, pentafluorophenyl, strong cation-exchange, and HILIC columns. The trend toward fast chromatography is investigated, both UHPLC and HPLC with appropriate arrangements moreover, results obtained with different ion sources, ESI, A PCI, and APPI are compared. 

Pentafluorophenyl propargyl ether isomerizes in the gas phase on silica gel at 370°C to give 2-monofluoromethyl-4,5,6,7-tetrafluorobenzo[6]-furan [81JCS(P1)1417]. Via the same route, naphtho[2,l-/ ]furans [82JCS(P1)107, 82JFC(20)173] and 4,5,6,7-tetrafluoro-2,3-dihydro-2-methyl-1-benzothiophene [81JCS(P1)1659] can be synthesized (Scheme 54). 

S. L. Richheimer, M. C. Kent, and M. W. Bernart, Reversed-phase high-performance liquid chromatographic method using a pentafluorophenyl bonded phase for analysis of tocopherols,/. Chromatogr. A 677 (1994), 75-80. 

EtMgBr (23 mmol, 23 mL of a I M THF soln) was added dropwise to bromobis(pentafluorophenyl)phos-phanc (27 8.9 g. 20 mmol) in THF (20 mL) over a period of ca. 20 min whilst cooling with an ice bath. After the addition was complete, a dark-brown solution with a precipitate was observed. After an additional 20 min, the mixture was treated wtih 6 M HC and Et20 was added. The phases were separated, and the organic layer was washed additionally with H20 (3 x ) and dried (MgS04). On evaporation of the solvent, 6.9 g of a residua liquid resulted. F ractional distillation gave 28 yield 4.7 g (59%) bp 97-98 C/0.7 Torr. 

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