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PubMed2006

Vibrational spectroscopy investigation using ab initio and density functional theory analysis on the structure of 3-aminobenzotrifluoride.

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 3-aminobenzotrifluoride. The FT-Raman and Fourier transform infrared spectra of 3-aminobenzotrifluoride (3ABTF) were recorded in the liquid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, depolarization ratios, reduced masses were calculated by HF and density functional B3LYP method with the 6-31G(d,p) and 6-311G(d,p) basis sets. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-31G(d,p)/6-311G(d,p) and B3LYP/6-31G(d,p)/6-311G(d,p) levels of theory. A detailed interpretations of the infrared and Raman spectra of 3ABTF is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.

Amines↗
PubMed1988

Ternary hydroxide complexes in neutral solutions of Al3+ and F-.

Especially in G protein systems AlF4- has been claimed as an activating species serving as a tetrahedral phosphate analog. However, in aqueous solutions (H2O)2AlF4- is hexacoordinate with two bound water molecules. In neutral solutions five different mixed OH- and F- complexes of Al3+ comprise the main species under usual experimental conditions. Comparison of the mole fraction distribution curves with limited results on the activity as a function of ambient F- concentrations suggests an activating complex composed of Al3+ with three F- and uncertain geometry. Even fewer activity data suggest a tetrahedral Be2+ complex with three F-.

Aluminum↗
PubMed2000

Assay of zofenopril and its active metabolite zofenoprilat by liquid chromatography coupled with tandem mass spectrometry.

Zofenopril is a pro-drug designed to undergo metabolic hydrolysis yielding the active free sulfhydryl compound zofenoprilat, which is an angiotensin converting enzyme (ACE) inhibitor, endowed also with a marked cardioprotective activity. A simple, highly sensitive specific LC-MS-MS method was developed for the determination of zofenopril and zofenoprilat in human plasma. In order to prevent oxidative degradation of zofenoprilat and its internal standard, their free sulfhydryl groups were protected by treatment with N-ethylmaleimide (NEM), which produced the succinimide derivatives. The compounds and their corresponding fluorine derivatives, used as internal standards, were extracted from plasma with toluene. The reconstituted dried extracts were chromatographed and then monitored by a triple-stage-quadrupole instrument operating in the negative ion spray ionization mode. The method was validated over the concentration range of 1-300 ng/ml for zofenopril and 2-600 ng/ml for zofenoprilat. Inter- and intra-assay precision and accuracy of both zofenopril and zofenoprilat were better than 10%. The limit of quantitation was 1 ng/ml with zofenopril and 2 ng/ml with zofenoprilat. Extraction recovery proved to be on average 84.8% with zofenopril and 70.1% with zofenoprilat. Similar recoveries were shown by the above two internal standards. The method was applied to measure plasma concentrations of zofenopril and zofenoprilat in 18 healthy volunteers treated orally with zofenopril calcium salt at the dose of 60 mg.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2002

The propargylic route as a short and versatile entry to optically active monofluorinated compounds.

Using selected models and appropriate NMR techniques, it has been demonstrated that dehydroxyfluorination in the propargylic position can be highly regio- and stereoselective. The corresponding propargylic fluorides are very useful intermediates for short preparations of stereodefined unsaturated or polyunsaturated compounds with a single fluorine atom in allylic or propargylic position. This strategy offers good means for the synthesis of chiral, nonracemic monofluorinated analogues of natural products.

Alkynes↗
PubMed2006

19F high magnetic field NMR study of beta-ZrF4 and CeF4: from spectra reconstruction to correlation between fluorine sites and 19F isotropic chemical shifts.

High magnetic field and high spinning frequency one- and two-dimensional one-pulse MAS 19F NMR spectra of beta-ZrF4 and CeF4 were recorded and reconstructed allowing the accurate determination of the 19F chemical shift tensor parameters for the seven different crystallographic fluorine sites of each compound. The attributions of the NMR resonances are performed using the superposition model for 19F isotropic chemical shift calculation initially proposed by Bureau et al. (Bureau, B.; Silly, G.; Emery, J.; Buzaré, J.-Y. Chem. Phys. 1999, 249, 85-104). A satisfactory reliability is reached with a root-mean-square (rms) deviation between calculated and measured isotropic chemical shift values equal to 1.5 and 3.5 ppm for beta-ZrF4 and CeF4, respectively.

Journal Article↗
PubMed2005

Syntheses and structures of hypervalent pentacoordinate carbon and boron compounds bearing an anthracene skeleton--elucidation of hypervalent interaction based on X-ray analysis and DFT calculation.

Pentacoordinate and tetracoordinate carbon and boron compounds (27, 38, 50-52, 56-61) bearing an anthracene skeleton with two oxygen or nitrogen atoms at the 1,8-positions were synthesized by the use of four newly synthesized tridentate ligand precursors. Several carbon and boron compounds were characterized by X-ray crystallographic analysis, showing that compounds 27, 56-59 bearing an oxygen-donating anthracene skeleton had a trigonal bipyramidal (TBP) pentacoordinate structure with relatively long apical distances (ca. 2.38-2.46 A). Despite the relatively long apical distances, DFT calculation of carbon species 27 and boron species 56 and experimental accurate X-ray electron density distribution analysis of 56 supported the existence of the apical hypervalent bond even though the nature of the hypervalent interaction between the central carbon (or boron) and the donating oxygen atom was relatively weak and ionic. On the other hand, X-ray analysis of compounds 50-52 bearing a nitrogen-donating anthracene skeleton showed unsymmetrical tetracoordinate carbon or boron atom with coordination by only one of the two nitrogen-donating groups. It is interesting to note that, with an oxygen-donating skeleton, the compound 61 having two chlorine atoms on the central boron atom showed a tetracoordinate structure, although the corresponding compound 60 with two fluorine atoms showed a pentacoordinate structure. The B-O distances (av 2.29 A) in 60 were relatively short in comparison with those (av 2.44 A) in 59 having two methoxy groups on the central boron atom, indicating that the B-O interaction became stronger due to the electron-withdrawing nature of the fluorine atoms.

Journal Article↗
PubMed2004

Just add water: a new fluorous capping reagent for facile purification of peptides synthesized on the solid phase.

A novel fluorous capping reagent is introduced to facilitate purification during solid-phase peptide synthesis (SPPS). Reagent 1 is a trivalent iodonium salt that reacts vigorously with free amines to deliver a long-chain fluoroalkyl group. It has been used to tag all unreacted amines following the peptide coupling step in SPPS. The resulting fluoroalkylated amine is no longer able to couple in further peptide coupling steps and is also stable to standard peptide synthesis conditions. Deletion products are removed using flash fluorous chromatography to yield the pure, full-length peptide.

Chromatography, High Pressure Liquid↗
PubMed2006

Facile Ar-CF3 bond formation at Pd. Strikingly different outcomes of reductive elimination from [(Ph3P)2Pd(CF3)Ph] and [(Xantphos)Pd(CF3)Ph].

Facile and highly selective perfluoroalkyl-aryl reductive elimination from a metal center (Pd) has been demonstrated for the first time. At temperatures as low as 50-80 degrees C, [(Xantphos)Pd(Ph)CF3] undergoes remarkably clean decomposition to produce CF3Ph in high yield and selectivity. In contrast, analogous trifluoromethylpalladium aryls stabilized by rigid cis-chelating ligands such as dppe are completely unreactive at temperatures up to 130-140 degrees C. Decomposition of [(Ph3P)2Pd(Ph)CF3] in the presence of PhI in benzene at 60 degrees C does not produce PhCF3 but rather leads to [(Ph3P)2Pd(Ph)I] and [Ph4P]+[(Ph3P)Pd(CF3)3]- in a 2:1 ratio with high selectivity.

Crystallography, X-Ray↗
PubMed1993

18F-labeled benzamides for studying the dopamine D2 receptor with positron emission tomography.

Two series of (N-benzylpiperidin-4-yl)- and (9-azabicyclo[3.3.1]nonan- 3 beta-yl)benzamides were prepared, and in vitro binding assays were used to measure the affinity of these compounds for dopamine D2, dopamine D3, serotonin 5-HT2, and alpha 2-adrenergic receptors. The results of these studies indicated compounds 23, 26b, and 34 have the selectivity needed for in vivo studies of the D2 (and possibly D3) receptors. 18F-Labeled analogues of 23, 26b and 34 were prepared by N-alkylation of the corresponding desbenzyl precursors with [18F]-4-fluorobenzyl iodide. Preliminary in vivo studies demonstrated that [18F]-23 and [18F]-26b are suitable candidates for further evaluation in positron emission tomography imaging studies. The slow rate of washout of [18F]-34 from nondopaminergic regions and its comparatively high lipophilicity indicates that this compound may not be suitable for imaging studies because of a high level of nonspecific binding.

Animals↗
PubMed2002

Potent, novel in vitro inhibitors of the Pseudomonas aeruginosa deacetylase LpxC.

Deacetylation of uridyldiphospho-3-O-(R-hydroxydecanoyl)-N-acetylglucosamine by LpxC is the first committed step in the Pseudomonas aeruginosa biosynthetic pathway to lipid A; homologous enzymes are found widely among Gram-negative bacteria. As an essential enzyme for which no inhibitors have yet been reported, the P. aeruginosa LpxC represents a highly attractive target for a novel antibacterial drug. We synthesized several focused small-molecule libraries, each composed of a variable aromatic ring, one of four heterocyclic/spacer moieties, and a hydroxamic acid and evaluated the LpxC inhibition of these compounds against purified P. aeruginosa enzyme. To ensure that the in vitro assay would be as physiologically relevant as possible, we synthesized a tritiated form of the specific P. aeruginosa glycolipid substrate and measured directly the enzymatically released acetate. Several of our novel compounds, predominantly those having fluorinated substituents on the aromatic ring and an oxazoline as the heterocyclic moiety, demonstrated in vitro IC(50) values less than 1 microM. We now report the synthesis and in vitro evaluation of these P. aeruginosa LpxC inhibitors.

Amidohydrolases↗
PubMed2003

Synthesis of two fluoro analogues of the nicotinic acetylcholine receptor agonist UB-165.

Two racemic fluoropyridine analogues 4 and 5 of the potent nicotinic agonist UB-165 have been synthesized. Halogenated pyridines 7 and 12 provided the organometallic reagents needed for the Negishi and Suzuki coupling reactions used for the preparation of 4 and 5, and the N-vinyloxycarbonyl protecting group of 8 and 15 was cleaved using a novel trifluoroacetic acid-mediated deprotection protocol. Analogue 4 retained high binding affinity at rat brain alpha4beta2 and alpha7 nicotinic receptors.

Animals↗
PubMed2005

Regio- and stereoselective reactions of gem-difluorinated vinyloxiranes with heteronucleophiles.

[Reaction: see text]. Regio- and stereoselectivity in reactions of gem-difluorinated vinyloxiranes with heteronucleophiles were successfully controlled. Halogen atoms were introduced regioselectively at the allylic epoxide carbon with an inversion in stereochemistry using MgBr2*Et2O or Li2CuCl4 to produce anti-vic-halohydrine. The other diastereomers were obtained selectively using LiBr/AcOH or BCl3, and SN2' type products were formed selectively with excellent E preference by changing the reaction temperature. Moreover, a further investigation led us to find that a regio- and stereoselective SN2' addition of several Brnsted acids was dependent on the pKa values of the acids. Under strong acidic conditions, we exclusively obtained E allylic alcohols.

Arabinose↗
PubMed2007

Practical stereoselective synthesis of an alpha-trifluoromethyl-alpha-alkyl epoxide via a diastereoselective trifluoromethylation reaction.

A practical stereoselective synthesis is reported for an alpha-trifluoromethyl-alpha-alkyl epoxide (1), which is an important pharmaceutical intermediate. The key step involves a chiral auxiliary-controlled asymmetric trifluoromethylation reaction for the introduction of the unique trifluoromethyl-substituted tertiary alcohol stereogenic center in the target molecule. The fluoride-initiated CF3 addition to chiral keto ester 6a proceeded with a diastereoselectivity up to 86:14. The major diastereomer was readily obtained with a >99.5:0.5 dr through a simple crystallization of the crude product mixture.

Alkylation↗