Search results for "SoMe"

Cyclocondensation reaction of 1,2-diamino-4-methylbenzene andp-substituted acetophenones

1993

1,2-Diamino-4-methylbenzene 1 reacts in the presence of sulphuric acid with 4-substituted acetophenones 2a-e yielding 2,4-diaryl-2,3-dihydro-2,8-dimethyl-1H-1,5-benzodiazepines 3a-e and as minor component 2,4-diaryl-2,3-dihydro-2,7-dimethyl-1H-1,5-benzodiazepines 4a-e. The ratio 3:4 is in the range of 7:3. The structure determination of the regioisomers was performed by NOE measurements.

Stereoselective Synthesis of (+)-Boronolide

2002

The delta-lactone boronolide (+)-1, a pharmacologically active, naturally occurring product, has been synthesized in enantiopure form with L-erythrulose as the chiral starting material. The key steps of the synthesis were a highly stereoselective aldol-reduction one-pot sequence, an indium-mediated diastereoselective aldehyde allylation, and a ring-closing metathesis.

Rigidified Calixarenes Bearing Four Carbamoylmethylphosphineoxide or Carbamoylmethylphosphoryl Functions at the Wide Rim

2000

Conformationally rigidified tetraCMPO derivatives have been prepared from calix[4]arene bis(crown ether) 4 a in which adjacent oxygens are bridged at the narrow rim by two diethylene glycol links. Acylation of the tetraamine 4 c with the CMPO-active ester 5 b gave the tetraphosphine oxide 6 a, while the tetraphosphinate 6 b and the tetraphosphonate 6 c were obtained by Arbuzov reaction of tetrabromoacetamido derivative 7 with PhP(OEt)2 or P(OEt)3. The extraction ability of these CMPO derivatives was checked for selected lanthanides and actinides and compared with the analogous compounds 1 b, 10 b and 10 d derived from calix[4]arene tetrapentyl ether. All rigidified bis(crown ether) ligands …

New high-performance liquid chromatography-based methodology for monitoring the conformational transitions of self-associating hydrophobic peptides, …

1988

A new high-performance size-exclusion chromatographic strategy is reported for the analysis of the hydrophobic self-associating peptide gramicidin A, incorporated into artificial phospholipid vesicles (liposomes). The method is based on the direct injection of a few microlitres of the gramicidin A-containing liposome suspension into the column, which is eluted with a non-polar solvent, such as tetrahydrofuran. The type and amount of information which can be derived from this methodology have been evaluated. Using this chromatographic approach, a correlation has been unambiguously shown to exist between the organization of the peptide in the vesicles and a number of variables involved in the…

Kinetics of Molecule Transfer between Lipid Vesicles and β-Cyclodextrins

1996

Abstract We propose a calorimetric method based on the van't Hoff model of depression of the freezing temperature to investigate slow kinetics involving lipid vesicles (liposomes) and drug–β-cyclodextrin (Cyd) complexes. Some nonsteroidal antiinflammatory drugs (NSAIDs) were examined and standard phospholipid liposomes were used in our experiments. Three different kinetic processes were investigated: (a)9Transfer of drugs from water-soluble Cyd-complexes to void liposomes. (b)9Uptake of drugs from the surface of liposomes by free Cyd dissolved in the aqueous phase. (c)9Exchange of drugs from loaded to void vesicles, and the effect of free Cyd in enhancing such a transfer. Most experiments w…

Polymeric Micelles and Liposomes as Potential Drug Carriers

1986

In the past, a whole aray of polymeric carriers for biologically active substances have been reported. In this field the main interest has focused on the use of randomly solubilized polymers. Naturally occuring amphiphilic transport proteins can be modelled by synthetic micellar solubilized polymers. Poly(ethylene oxide)-polypeptide block copolymers with hydrophobic and cyclophosphamide-containing side groups are described. These micellar systems are able to transport different hydrophobic drugs.

How to Bridge the Gap Between Membrane Biology and Polymer Science

1986

Can polymer chemists contribute to the understanding or even mimicking of cell membrane functions and cell-cell interactions? Fascinated by the specificity and efficiency of, for example, the destruction of tumor cells by lymphocytes (1) and having in mind what biochemical analyses tell us about membrane composition, we may try to “synthesize” membrane and cell models. The commonly used model systems, such as planar lipid monolayers at the gas-water interface, bimolecular lipid membranes and spherical liposomes, are much less stable than natural membrane systems (Figure 1).

Polymeric monolayers and liposomes as models for biomembranes. How to bridge the gap between polymer science and membrane biology?

1984

This contribution deals with the stabilization of membrane model systems, especially vesicles. The desired further biological functionalization of these stabilized polymeric membranes is possible via the incorporation of proteins. Addition of natural lipids to polymerizable membranes and degradation of the unpolymerized component after polymerization allows selective opening of otherwise stable compartments. Finally, first attempts are made to combine biological properties of natural cells and the durability of polymerized membranes via fusion of synthetic vesicles with natural cells.

1984

Different polymeric transport systems for biologically active substances are presented. In the past, most of the reviews on polymeric drugs dealt with pharmaca, fixed to conventional water-soluble polymers. Naturally occuring transport proteins with their complex features have recently been imitated by micellar solubilized polymers. Polymerized liposomes from polymerizable lipids can be regarded as vesicular solubilized polymers and are discussed as stable models for biomembranes. By insertion of glycolipids, these liposomes are rendered susceptible to specific recognition by proteins. When natural or cleavable synthetic lipids are incorporated into polymerizable membranes, phase-separation…

α,β-Poly(N-Hydroxyethyl)-DL-Aspartamide Hydrogels as Drug Delivery Devices

1996

α,β-poly(N-hydroxyethyl)-DL-aspartamide (PHEA) was exposed to gamma radiation to obtain micromatrices able to swell in an aqueous medium. Crosslinked PHEA was loaded with an anti-inflammatory drug, 4-biphenylacetic acid (BPAA) and the drug dispersion in the network was investigated by X-ray analysis. The BPAA loaded PHEA microparticles were also characterized by dimensional analysis, which showed the presence of quasispherical shapes. The drug release from PHEA hydrogel was studied in vitro in a pH 1.1 (simulated gastric juice) and in a pH 7.4 buffer solution, respectively. The experimental data indicate that an anomalous delivery occurs, but Fickian diffusion through swollen PHEA hydrogel…