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Benzyl Groups (benzyl + groups)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Synthesis and Extraction Properties of Oxathiacrown Compounds Containing Benzyl Groups.

CHEMINFORM, Issue 45 2006
N. A. Rezekina
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Pseudorotaxanes and Rotaxanes Formed by Viologen Derivatives

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2006
Adam B. Braunschweig
Abstract Dibenzyl-4,4,-bipyridinium (BIPY2+) bis(hexafluorophosphate) and three of its derivatives , disubstituted at the para positions of the benzyl groups with CO2Me, F, and Me in turn , have been shown to form 1:1 complexes that are [2]pseudorotaxanes with dibenzo[24]crown-8 (DB24C8), benzometaphenylene[25]crown-8 (BMP25C8), and dipyrido[24]crown-8 (DP24C8) in CD3CN solution by 1H NMR spectroscopy and in one case in the solid state by X-ray crystallography. Binding constants (Ka) for all of these 1:1 complexes, which were determined both (1) by isothermal titration calorimetry in MeCN solution and (2) by the 1H NMR spectroscopic single-point method in CD3CN solution, were found to be, on the average, an order of magnitude less than the Ka values obtained for DB24C8 and DP24C8 with dibenzylammonium (DBA+) hexafluorophosphate and three of its derivatives, also disubstituted at the para positions of the benzyl groups with CO2Me, F and Me. In the case of BMP25C8, however, the Ka values with both categories (BIPY2+ and DBA+) of guests are much of a muchness, being both small and error prone. The equilibrium thermodynamics for these small libraries of [2]pseudorotaxanes indicate that the best bistable [2]rotaxanes incorporating both DBA+ and BIPY2+ recognition sites are going to involve ester functions in their dumbbell components and will employ DP24C8 or, failing that, DB24C8 as the ring component. The BIPY2+threads also directed the templated assembly of [2]rotaxanes incorporating the crown ethers (DB24C8, DP24C8, and BMP25C8) and triphenylphosphonium stoppers using the threading followed by stoppering approach. The rotaxanes were characterized in solution by 1H NMR spectroscopy, and in one case, in the solid state by X-ray crystallography.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Microwave-assisted TFA cleavage of peptides from Merrifield resin

JOURNAL OF PEPTIDE SCIENCE, Issue 1 2010
Alicja Kluczyk
Abstract Microwave-assisted (MW) reactions are of special interest to the chemical community due to faster reaction times, cleaner reactions and higher product yields. The adaptation of MW to solid phase peptide synthesis resulted in spectacular syntheses of difficult peptides. In the case of Merrifield support, used frequently in synthesis of special peptides, the conditions used in product cleavage are not compatible with off-resin monitoring of the reaction progress. The application of MW irradiation in product removal from Merrifield resin using trifluoroacetic acid (TFA) was investigated using model tetrapeptides and the effects were compared with standard trifluoromethanesulphonic acid (TFMSA) cleavage using elemental analysis as well as chromatographic (HPLC) and spectroscopic (IR) methods. The deprotection of benzyloxycarbonyl and benzyl groups in synthetic bioactive peptides was analyzed using LC-MS and MS/MS experiments. In a 5 min microwave-assisted TFA reaction at low temperature, the majority of product is released from the resin, making the analytical scale MW-assisted procedure a method of choice in monitoring the reactions carried out on Merrifield resin due to the short reaction time and compatibility with HPLC and ESI-MS conditions. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd. [source]

Synthetic and antimicrobial studies on new gold(I) complexes of imidazolidin-2-ylidenes

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2004
smail Özdemir
Abstract Six new 1,3-diorganylimidazolidin-2-ylidene (NHC) gold(I) complexes of the type [Au(NHC)2]+ (1,6), were synthesized by reacting [AuCl(PPh)3] with 1,3-dimesitylimidazolidin-2-ylidene or bis(1,3-dialkylimidazolidin-2-ylidene). The complexes 1,6 were fully characterized by elemental analyses and spectroscopic data. The placement of mesityl or para-substituted benzyl groups on the nitrogen atoms of the ring of the complexes leads to the particularly active antibacterial agents evaluated in this work. It is worth noting that the p -methoxybenzyl derivative (2) inhibited the growth of Pseudomona aeruginosa, Staphylococcus epidermidis, Staphylococcus aureus and Enterococcus faecalis with minimum inhibitory concentration (MIC) values of 3.12 µg ml,1, 6.25 µg ml,1, 3.12 µg ml,1 and 3.12 µg ml,1 respectively. In contrast, the analogous p -dimethylaminobenzyl derivative (3) is effective only against Escherichia coli (MIC = 3.12 µg ml,1). Copyright © 2004 John Wiley & Sons, Ltd. [source]

Synthesis, properties and crystal structural characterization of diorganotin(IV) derivatives of 2-mercapto-6-nitrobenzothiazole

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2003
Chunlin Ma
Abstract The diorganotin(IV) dichlorides R2SnCl2 (R: Ph, PhCH2 or n -Bu) react with 2-mercapto-6-nitrobenzothiazole (MNBT) in benzene to give [Ph2SnCl(MNBT)] (1), [(PhCH2)2Sn(MNBT)2] (2) and [(n -Bu)2Sn(MNBT)2] (3). The three complexes have been characterized by elemental analysis and IR, 1H, 13C and 119Sn NMR spectroscopies. X-ray studies of the crystal structures of 1, 2 and 3 show the following. The tin environment for complex 1 is distorted cis-trigonal bipyramid with chlorine and nitrogen atoms in apical positions. The structure of complex 2 is a distorted octahedron with two benzyl groups in the axial sites. The geometry at the tin atom of complex 3 is that of an irregular octahedron. Interestingly, intra-molecular non-bonded Cl,S interactions and S,S interaction were recognized in the crystallographic structures of 1 and 3 respectively. As a result, complex 1 is a polymer and complex 3 is a dimer. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Structure,Activity Study on the Spatial Arrangement of the Third Aromatic Ring of Endomorphins 1 and 2 Using an Atypical Constrained C,Terminus

CHEMMEDCHEM, Issue 3 2007
Ye Yu Dr.
Abstract The discovery of endomorphins (EMs) has opened the possibility of searching for new analgesics. However, the design of peptide analgesics has proven to be very difficult as a result of their conformational flexibility and a lack of clarity in structure,activity relationships (SAR). In EMs, the amino acid side chains exhibit considerable conformational flexibility, especially in the third aromatic ring, which is free to adopt a bioactive conformation. To resolve these problems, a series of C,terminus EM analogues, [Xaa4 -R]EMs, modified through the substitution of Phe4 with nonaromatic residues and termination with benzyl groups, were designed to generate conformational constrains of the third aromatic ring by amide bond and torsion angles (,4 and ,4) of Xaa4. Introduction of (S)-,-methyl or (S)/(R)-,-carboxamide on the methylene unit of the benzyl group was designed to produce an atypical topographical constraint (,5) of the third aromatic ring rotation. Interestingly, some EM derivatives, with elimination of the C-terminal carboxamide group and significant changes in the address sequence (Phe4 -NH2), still exhibited higher ,-opioid receptor (MOR) affinity than unmodified EMs. In contrast, some analogues with incorrectly constrained C,termini displayed very low affinity and pharmacological activities. Thus, our results indicate that these EM analogues, with atypical constrained C,termini, provide model compounds with potent MOR agonism. They also give evidence that the proper spatial orientation and conformational restriction of the third aromatic ring are crucial for the interaction of EMs with MOR. [source]