Search results for "Chemical Synthesis"
showing 10 items of 285 documents
Novel synthesis of spherical MCM-48
1999
Abstract A novel synthesis route was developed for the cubic member of the M41S family, MCM-48, with a three-dimensional pore system allowing the formation of submicrometre- to micrometre-sized beads with a narrow pore-size distribution. The synthesis is based on the modified Stober method applying tetraethoxysilane, ethanol, water, ammonia and n -hexadecyltrimethylammonium bromide as template. The specific surface area, the specific pore volume and the average pore diameter were varied in the following ranges: 900–1600 m 2 g −1 , 0.5–0.9 cm 3 g −1 and 2–3 nm. Aluminium-, chromium-, gallium-, niobium- and vanadium-MCM-48 were also synthesized following this procedure.
ELECTROCHEMICAL CONVERSION OF DICHLOROACETIC ACID TO CHLOROACETIC ACID IN A MICROFLUIDIC STACK AND IN A SERIES OF MICROFLUIDIC REACTORS
2015
The electrochemical conversion of dichloroacetic acid to chloracetic acid was performed in three different micro devices: a simple micro fluidic cell; a microfluidic stack equipped with various electrode chambers in series and three micro fluidic cells in series. The electrochemical synthesis of chloracetic acid was performed successfully with high yields and selectivity under a single-pass mode without supporting electrolyte at low cell voltages. An increase of the productivity and of the final concentration of the target product was achieved by using a stack with two or three electrode chambers in series. The utilization of three micro reactors in series open interesting new perspectives,…
Synthesis and radiosynthesis of N5-[18F]fluoroethyl-Pirenzepine and its metabolite N5-[18F]fluoroethyl-LS 75
2009
The well established M1 selective muscarinergic antagonist Pirenzepine 11-[2-(4-methyl-piperazin-1-yl)-acetyl]-5,11-dihydro-benzo[e]pyrido[3,2-b][1,4]diazepin-6-one (1) exhibits an unusual behaviour in vivo, which cannot be explained with M1 antagonism exclusively. One of the aspects discussed is a specific interaction with poly ADP-ribose polymerase (PARP-1). 1 undergoes metabolism to form LS 75 5,11-dihydro-benzo[e]pyrido[3,2-b][1,4]diazepin-6-one (2). In order to study deviations in Pirenzepine efficacy from pure M1 binding in vivo using PET, appropriate positron emitter labelled analogues of 1 and 2 were synthesised. Non-radioactive reference compounds 3 and 4 were tested for PARP-1 inh…
Cross-Metathesis Reactions as an Efficient Tool in the Synthesis of Fluorinated Cyclic β-Amino Acids
2009
The synthesis of enantiomerically pure, cyclic, gamma,gamma-difluorinated beta-amino acids with various ring sizes has been carried out with a cross-metathesis (CM) reaction being one of the key steps, followed by a Dieckmann-type condensation to bring about the cyclization. Subsequent catalytic hydrogenation under microwave irradiation with (-)-8-phenylmenthol as a chiral auxiliary led to the successful chemo- and diastereoselective chemical reduction of the resulting cyclic beta-enamino esters. The efficiency and scope of the CM reaction with different types of fluorinated imidoyl chlorides and unsaturated esters has also been studied in order to determine the optimal reaction conditions …
New Strategy for the Stereoselective Synthesis of Fluorinated β-Amino Acids
2002
Racemic and chiral nonracemic alpha-substituted and alpha-unsubstituted beta-fluoroalkyl beta-amino acid derivatives 6 and 9 have been synthesized in two steps starting from fluorinated imidoyl chlorides 1 and ester enolates. This approach is based on the chemical reduction of previously obtained gamma-fluorinated beta-enamino esters 4 by using ZnI(2)/NaBH(4) in a nonchelated aprotic medium (dry CH(2)Cl(2)) as the reducing agent. A metal-chelated six-membered model has been suggested to explain the stereochemical outcome of the reduction reaction. The process takes place with high yields and with moderate to good diastereoselectivity. The best results related to diastereoselective reduction…
3,4-trans-4-Aryl-3-(1-pyridinio)-1,2,3,4-tetrahydropyridine-6-thiolates—new group of potential cardiotonic drugs
2005
Abstract 3,4- trans -4-Aryl-3-(1-pyridinio)-1,2,3,4-tetrahydropyridine-6-thiolates 6 – 11 were prepared by a Michael reaction of N -acetonylpyridinium chloride with 3-aryl-2-cyanothioacrylamides or by a one-pot three-carbon condensation of N -acetonylpyridinium chloride, aromatic aldehyde and 2-cyanothioacetamide, and their cardiotonic properties were studied. 3,4- trans -5-cyano-2-hydroxy-2-methyl-4-(3-nitrophenyl)-3-(1-pyridinio)-1,2,3,4-tetrahydropyridine-6-thiolate 8 was considered as a lead compound in this series since it in vitro experiments (spontaneously beating rat atria) showed a cardiotonic activity similar to that of milrinone 2 , however compound 8 induced activity at lover co…
Synthesis and mutagenicity of the diastereomeric fjord-region 11,12-dihydrodiol 13,14-epoxides of dibenzo[a,l]pyrene.
1994
Extensive tumorigenicity studies in rodents revealed that dibenzo[a,l]pyrene (DB[a,l]P) is the most potent carcinogen among all polycyclic aromatic hydrocarbons (PAHs) tested so far. The structure of the genotoxic metabolite(s) responsible for this exceptional carcinogenicity is unknown. The fjord-region syn- and anti-DB[a,l]P-11,12-dihydrodiol 13,14-epoxides (syn- and anti-DB[a,l]PDE) were synthesized to clarify their role as possible ultimate mutagenic and carcinogenic metabolites of DB[a,l]P.9-Formyl-11,12-dimethoxybenzo[g] chrysene was prepared from 9-phenanthrylacetic acid by a photochemical route. After reaction of the aldehyde with trimethylsulfonium iodide to generate an oxiranyl si…
Synthesis and characterization of diorganotin(IV) complexes ofN-(2-pyridylmethylene)arylamines and mutagenicity testingin vivo of Et2SnCl2�[L4=N-(2-p…
1998
Diorganotin(IV) dichloride complexes of the type R 2 SnCl 2 .L (R = methyl, ethyl, vinyl, t-butyl, n-butyl or phenyl; L=N-(2-pyridylmethylene)arylamine) have been synthesized and characterized on the basis of IR, NMR and 119 Sn Mossbauer studies. Investigation of the complexes indicated that N-(2-pyridylmethylene)arylamines form distorted trans-octahedral complexes with R 2 SnCl 2 similar to the well-known R 2 SnCl 2 .L. Cytogenetic toxicology testing has been performed for Et 2 SnCl 2 .L 4 [L 4 = N-(2-pyridylmethylene)-4-toluidine] in mouse bone-marrow cells in vivo since such testing is a regulatory requirement before new drugs are released. This tin compound induced delay in cell-cycle k…
Enhanced β-turn conformational stability of tripeptides containing Δphe in cis over trans configuration
2013
Conformations of three pairs of dehydropeptides with the opposite configuration of the Delta Phe residue, Boc-Gly-Delta(Z/E)Phe-Phe-p-NA (Z- p -NA and E- p -NA), Boc-Gly-Delta(Z/E)Phe-Phe-OMe (Z-OMe and E-OMe), and Boc-Gly-Delta(Z/E)Phe-Phe-OH (Z-OH and E-OH) were compared on the basis of CD and NMR studies in MeOH, TFE, and DMSO. The CD results were used as the additional input data for the NMR-based calculations of the detailed solution conformations of the peptides. It was found that Z- p -NA, E- p -NA, Z-OMe, and Z-OH adopt the beta-turn conformations and E-OMe and E-OH are unordered. There are two overlapping type III beta-turns in Z- p -NA, type II' beta-turn in E- p -NA, and type II …
Di- and Tri-organotin(IV) Complexes ofN-Acetyltriglycine andN-Benzoyltriglycine: Synthesis and Spectroscopic Characterization
1996
Di- and tri-organotin(IV) derivatives of N-acetyltriglycine and N-benzoyltriglycine (HA) were obtained by refluxing equimolar mixtures of the ligand and the organotin(IV) oxide or hydroxide in methanol or acetone. According to the spectroscopic data, triorganotin(IV) derivatives adopt a trigonal-bipyramidal structure in which the planar R 3 Sn IV unit is bonded by a monodentate carboxylate group and a donor group, presumably the amide C=O. The reaction of HA with the appropriate diorganotin(IV) compounds gave both dicarboxylates R 2 SnA 2 , with six-coordinated tin, and dimeric tetra-organodistannoxanes {[R 2 SnA] 2 O}2, in which the tin atoms are essentially five-coordinated.