Search results for "deriva"
showing 10 items of 1423 documents
Separation of Proteic Primary Amino Acids under Several Reversed‐Phase Liquid Chromatographic Conditions
2006
Abstract The reversed‐phase liquid chromatographic (RPLC) analysis of proteic primary amino acids with acetonitrile‐water, using pre‐column derivatisation with o‐phthalaldehyde (OPA) and N‐acetylcysteine (NAC), was compared with RPLC modes using trifluoroacetic acid or pentadecafluorooctanoic acid and evaporative light‐scattering detection, or sodium dodecyl sulphate micelles with pre‐ and post‐column derivatisation. The importance of column lifetime, risk of potential damages in the instrumentation, retention and resolution, was considered. Among the assayed approaches, the best is still aqueous‐organic RPLC with pre‐column derivatisation. It not only yields the most reliable results, but …
Enzyme class identification in cleaning products by hydrolysis followed by derivatization with o-phthaldialdehyde, HPLC and linear discriminant analy…
2008
The enzymes present in raw materials of the cleaning industry (enzyme industrial concentrates) and in household cleaners were isolated by precipitation with acetone and hydrolyzed with HCl. The resulting amino acids were derivatized with o-phthaldialdehyde, and the derivatives were separated by HPLC. The peaks of 14 amino acids were observed using a C18 column and a multi-segmented gradient of acetonitrile-water in the presence of a 5 mM citric/citrate buffer of pH 6.5. Using either normalized peak areas (divided by the sum of the peak areas of the chromatogram) or ratios of pairs of peak areas as predictor variables, linear discriminant analysis models, capable of predicting the enzyme cla…
Conformational characteristics of homo-oligopeptides of O-benzyl-L-tyrosine+
1983
Conformational studies of X[-L-Tyr(Bzl)-]n-series bound to polyethyleneglycol (X = H2, Nps; n = 3-8) in the solid state and in solvents of different polarities and capabilities of forming hydrogen bonds are reported. By using i.r. absorption, the occurrence of the beta-structure in the higher oligomers in the solid state was established. By means of i.r. absorption and CD the onset of that ordered conformation in solution was assessed as a function of chain length. The effects induced by the presence of the N-protecting group and added base, and by changing the nature of solvent on the conformational preferences of the [-L-Tyr(Bzl)-]n homo-peptides were also examined. The 2-nitrophenylsulph…
Enantioselektive Trifluoracetylierung mit Hilfe chiraler Polyamide
1980
(S)-Poly(2-aminobutyric acid) (1) [(S)-poly(imino-1-methyl-3-oxotrimethylene)] was transformed into its N-trifluoroacetyl derivative 4. The IR spectra and the circular dichroism of both substances were compared. In addition, (S)-poly[N-(1-phenylethyl)acrylamide] (2) ((S)-poly-[1-(1-phenylethylaminocarbonyl)ethylene]) was trifluoroacetylated leading to polymer 5. 4 was found to react as trifluoroacetylating agent with L-1-phenylethylamine (L-3) twice as fast as it reacts with D-3. Accordingly, the reaction of 4 with D,L-3 leads preferentially to the L-form of N-(1-phenylethyl)trifluoroacetamide with optical yields up to 6%. The reaction of 5 with D,L-3 affords the D-form of N-(1-phenylethyl)…
Polythiophene S,S dioxides: an investigation on electrochemical doping
2000
Abstract A new strategy for functionalizing oligothiophenes is the transformation of the thienyl sulphurs into the corresponding S,S dioxides, with the effect of lowering the LUMO energy without significantly affecting the HOMO one. From a quinquethiophene S,S dioxide derivative, a polymer (pQTDO) which can be reversibly n-doped at not very negative potentials still maintaining the property of being p-doped at moderate potential values was electrosynthesized. There is, however, a great difference in the ability to store charge of the polymer’s p- and n-doped forms: a great amount of injected negative charge irreversibly modifies the structure of pQTDO.
Large Scale Synthesis of Mono- and Di-urethane Derivatives of Lysine.
1999
Orthogonally protected diurethane derivatives of lysine are valuable materials for peptide syntheses. An example is ZLys(Boc), which is exploited in the industrial production of certain well-established peptide drugs. 3,4) Another derivative is Fmoc-Lys(Boc), which is in common use in the laboratory synthesis of peptides. 5) The simplest route to these lysine derivatives seems to be using the copper complex for simultaneous protection of the a-amino and a-carboxyl function, N e -tert-butoxycarbonylation and then copper detachment. The obtained Lys(Boc) might be then subjected to N a -benzyloxycarbonylation.
N-(2-Benzoyl-4-chlorophenyl)-4-chlorobenzenesulfonamide
2008
The title compound, C19H13Cl2NO3S, is an N-arylsulfonyl derivative of 2-amino-5-chlorobenzophenone. The compound is biologically active and shows potential to be utilized as an inhibitor of CCR2 and CCR9 receptor functions. In the crystal structure, there is an intramolecular N—H...O hydrogen bond between the amide and carbonyl groups. The benzoyl and 4-chlorophenyl groups form intramolecular and intermolecular face-to-face contacts, with a dihedral angle of 10.6 (1)° between their mean planes in both cases, and centroid–centroid separations of 4.00 (1) and 4.25 (1) Å for the intra- and intermolecular interactions, respectively.
Capping α-Cyclodextrin with Cyclotriveratrylene by Triple Disulfide-Bridge Formation
2013
Disulfide-bond formation is an expeditious coupling reaction to make macropolycyclic symmetrical receptors. It is used here for the preparation of unsymmetrical cavitands based on α-cyclodextrin (α-CDX) and cyclotriveratrylene (CTV) analogues. Accordingly, diastereomeric hemicryptophanes 2a and 2b were obtained in 11 % isolated yield by the iodine oxidation of a 1:1 mixture of racemic cyclotrithiophenolene (3) and the C3-symmetric trithiol derivative of permethylated α-cyclodextrin (PM α-CDX) 4. Remarkably, the target hemicryptophanes were obtained in a 5:3 diastereomeric ratio. The reaction produced mainly (34 %) a singly disulfide-bridged PM α-CDX dimer 7, however no traces of triply disu…
Determination of optical purity of phosphonic acid analogues of aromatic amino acids by capillary electrophoresis with alpha-cyclodextrin.
2000
A simple and efficient method for the determination of enantiomeric purity of structurally diverse phosphonic and phosphinic acid analogues of phenylalanine and phenylglycine using capillary electrophoresis is presented. These preliminary studies indicated that the enantiomer separation is strongly dependent on the structure of the aminophosphonic acid.
Twisting of the resorcinarene core due to solvent effects upon crystallization
2009
The effect of the crystallization conditions on the conformation of the tetramethoxy resorcinarene skeleton was investigated in acetone solutions, to which was added a second component (less favorable solvent or salt) to promote crystallization. The resorcinarene core was found to adopt three different conformations: crown (I), a pinched crown (II) and a twisted pinched crown (III). In addition, the flexibility of the resorcinarene core was compared with a tetramethoxy resorcinarene derivative, resorcinarene bis-crown, which is in a fixed boat conformation.