Search results for "Reaction"
showing 10 items of 6134 documents
Clickable poly-L-lysine for the formation of biorecognition surfaces
2019
Biomolecules are immobilized onto surfaces employing the fast and stable adsorption of poly-l-lysine (PLL) polymers and the versatile copper-free click chemistry reactions. This method provides the combined advantages of versatile surface adsorption with density control using polyelectrolytes and of the covalent and orthogonal immobilization of biomolecules with higher reaction rates and improved yields of click chemistry. Using DNA attachment as a proof of concept, control over the DNA probe density and applicability in electrochemical detection are presented.
PCR-Based Site-Specific Mutagenesis
1998
The alteration of gene structure through the substitution of specific nucleotides by site-specific mutagenesis is an important tool in modern recombinant DNA technology. Nucleotide changes are necessary not only for the analysis of the structural basis of gene and corresponding protein function, but also for the generation of novel gene products. The availability of the polymerase chain reaction (PCR) in the last decade has enabled the modification of DNA for different needs to be made more rapidly and easily than was previously possible. In the course of mutagenesis the relevant sequence changes can be introduced more readily by chemically synthesized oligonucleotide primers than by manipu…
Convenient Synthesis of Biologically Important Retinoids
1995
The toxic and teratogenic effects caused by the highly biologically active (all-E)-retinoic acid and its derivatives prompted us to synthesize a number of retinoids. We developed synthetic approaches to (all-E)-retinyl β-D-glucuronide 3, methyl (retinoyl β-D-glucopyranoside)uronate 5, (all-E)-retinoic acid β-D-glucopyranosyl ester 8 and (all-E)-retinoyl β-D-glucuronide 6 in high purity and yield. Compound 3 was synthesized under Koenigs-Knorr conditions from (all-E)-retinol and an α-halogenose. Compounds 5 and 8 were prepared by esterification of a silver salt of (all-E)-retinoic acid with an α-glycosyl halide in pyridine. (all-E)-Retinoyl β-D-glucuronide 6 was prepared by reaction of (all-…
Counterion's Effect on the Catalytic Activity of Zn-Prolinamide Complexes in Aldol Condensations
2012
The catalytic activity of complexes involving organic ligands and Lewis acids can be modulated by changing any of their components. In this work we have studied the influence on the stereoselectivity and catalytic activity exerted by the counterion of zinc salts employed as cocatalysts of L-prolinamide in aldol condensations. The structures of the complexes have been determined both in solution and in the solid state.
Bis(oxamato)palladate(II) complexes: synthesis, crystal structure and application to catalytic Suzuki reaction
2015
New bis(oxamato)palladate(II) complexes, [Pd(H2O)4][Pd(2,6-Me2pma)2]·2H2O (1), (n-Bu4N)2[Pd(2,6-Me2pma)2]·2H2O (2a), and (n-Bu4N)2[Pd(2,6-Me2pma)2]·2CHCl3 (2b) (2,6-Me2pma = N-2,6-dimethylphenyoxamate and n-Bu4N+ = tetra-n-butylammonium), have been synthesized and the structures of 1 and 2b characterized by single-crystal X-ray diffraction. Complex 1 is a double salt constituted by tetraaquapalladium(II) cations and bis(oxamato)palladate(II) anions interlinked by hydrogen bonds. The palladium(II) ions in 1 are four-coordinate with two oxygens and two nitrogens from two fully deprotonated oxamate ligands (anion), and four water molecules (cation) building centrosymmetric square-planar surrou…
Model studies on a diastereoselective synthesis of the C(33)–C(37) fragment of Amphotericin B
2003
Abstract A new, short and highly diastereoselective synthetic route aiming at the C(33)–C(37) fragment of Amphotericin B has been developed. Studies with a model aldehyde (benzaldehyde) have given very promising results: the desired stereochemistry of all four stereocenters of the target molecule has been achieved with high diastereoselection. The stereochemistry of three key intermediates and the target segment has been confirmed by X-ray crystallography.
ChemInform Abstract: Reactions of the Hydrofluoroborate Salts of Open-Chain Analogues of Reissert Compounds with Some α,β-Ethylenic Esters.
2010
The reaction of the hydrofluoroborate salt of an open-chain analogue of a Reissert compound with some α,β-ethylenic esters does not give a [4 + 2] cycloadduct, as previously described in the case of ethyl acrylate. The reaction starts with a 1,3-dipolar cycloaddition of a munchnone imine 5c, d. The [3 + 2] cycloadducts 13 evolve via a rearrangement–condensation sequence to give a substituted 2-pyridone derivative 18 or 19. The proposed mechanism has been verified by the isolation and structural X-ray analysis of some compounds of the reaction sequence.
ChemInform Abstract: Studies on the Biosynthesis of Paraherquamide. Construction of the Amino Acid Framework.
2010
Abstract It has been previously established in this laboratory that the β-methyl-β-hydroxyproline moiety of the potent anthelmintic agent paraherquamide A, is biosynthetically derived from l -isoleucine. The downstream events from l -Ile to paraherquamide A have now been investigated. The synthesis of [1- 13 C]-labeled l -β-methylproline is described by means of a Hoffman–Loeffler–Freytag reaction sequence from [1- 13 C]- l -Ile. This amino acid is shown to be a direct biosynthetic precursor to paraherquamide A by feeding and incorporation experiments in growing cultures of Penicillium fellutanum . Three tryptophan-containing dipeptides of l -β-methylproline have been constructed: [ 13 C 2 …
Thermo-, piezo-, photo- and chemo-switchable spin crossover iron(II)-metallocyanate based coordination polymers
2011
Abstract The design of coordination polymers (CPs) with switch and memory functions is an important subject of current interest in the search for new advanced materials with potential applications. Implementation of CPs with electronically labile iron(II) building blocks able to undergo cooperative spin crossover (SCO) behavior is a singular approach to this end. This review provides an up to date survey of a new generation of iron(II)-metallocyanate based spin crossover coordination polymers (SCO-CPs) developed during the last decade. These new solids feature structural diversity, supramolecular isomerism, interpenetrating frameworks, structure flexibility, reversible solid-state chemical …
Der (2-Phenyl-2-trimethylsilyl)ethyl-(PTMSE)-Ester – eine neutral spaltbare Carboxyschutzgruppe/The (2-Phenyl-2-trimethylsiylyl)ethyl (PTMSE) Ester –…
2002
(2-Phenyl-2-trimethylsilyl)ethyl (PTMSE) esters of aminoacids and peptides are stable under the conditions of hydrogenolytic cleavage of benzoxycarbonyl(Z) and benzyl ester groups, base-induced removal of Fmoc groups, palladium(0)-catalyzed removal of allyloxycarbonyl (Aloc) and even acidolytic cleavage of Boc groups. PTMSE esters are also stable under the conditions of peptide condensation reactions. The PTMSE ester is selectively cleaved by treatment with tetrabutylammonium fluoride (TBAF) trihydrate in dichloromethane, i. e. under almost neutral conditions, within a few minutes and, therefore, considered a valuable novel carboxy protecting group.