Search results for "Trim"
showing 10 items of 1942 documents
ChemInform Abstract: The Synthesis and Effect of Fluorinated Chalcone Derivatives on Nitric Oxide Production.
2010
Abstract Dimethoxy- and trimethoxychalcone derivatives, with various patterns of fluorination, were synthesized and evaluated for their influence on nitric oxide production. Some of them, chalcones 1 , 5 , 7 , 10 , 11 and 17 , inhibited NO production with an IC 50 in the submicromolar range; 17 is especially noteworthy because of its potency (IC 50 30 nM). These effects were not the consequence of a direct inhibitory action on enzyme activity but the inhibition of enzyme expression.
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.
Reversed-phase liquid chromatography without organic solvent for determination of tricyclic antidepressants
2012
The chromatographic behavior of seven tricyclic antidepressants (amitryptiline, clomipramine, doxepin, imipramine, maprotiline, nortryptiline, and trimipramine) was examined with micellar mobile phases containing the nonionic surfactant Brij-35. Acetonitrile-water mixtures were also used for comparison purposes. Tricyclic antidepressants are moderately polar basic drugs, which are positively charged in the usual working pH. This gives rise to a strong association with the alkyl chains and residual ionized silanols in silica-based stationary phases, which is translated in a high consumption of organic solvent to get appropriate retention times. Brij-35 modifies the surface of the stationary …
Superchiral Pd 3 L 6 Coordination Complex and Its Reversible Structural Conversion into Pd 3 L 3 Cl 6 Metallocycles
2015
Large, non-symmetrical, inherently chiral bispyridyl ligand L derived from natural ursodeoxycholic bile acid was used for square-planar coordination of tetravalent Pd(II) , yielding the cationic single enantiomer of superchiral coordination complex 1 Pd3 L6 containing 60 well-defined chiral centers in its flower-like structure. Complex 1 can readily be transformed by addition of chloride into a smaller enantiomerically pure cyclic trimer 2 Pd3 L3 Cl6 containing 30 chiral centers. This transformation is reversible and can be restored by the addition of silver cations. Furthermore, a mixture of two constitutional isomers of trimer, 2 and 2', and dimer, 3 and 3', can be obtained directly from …
Rigid biobased polycarbonates with good processability based on a spirocyclic diol derived from citric acid
2020
Introducing biobased polymers from renewable sources for use as high-performance thermoplastics with high demands on mechanical rigidity, transparency, thermal stability, as well as good processability, is a significant challenge. In the present work we have designed and prepared a rigid biobased bis-spirocylic diol by di-cycloketalization of a bicyclic diketone (cis-bicyclo[3.3.0]octane-3,7-dione, obtained from citric acid) using trimethylolpropane. This spiro-diol monomer has two reactive primary hydroxyl groups and the synthesis from inexpensive biobased starting materials is straightforward and readily upscalable, involving no chromatographic purification. In order to explore the useful…
Das System 2‐Halogenethylester/Cholinester als Zweistufen‐Schutzgruppe für die Carboxylfunktion von Aminosäuren und Peptiden
1979
Das System 2-Chlorethyl- und 2-Bromethylester/Cholinester wird als Carbonsaure-Schutzfunktion beschrieben. Die 2-Chlorethyl-(OEt(Cl))- und die 2-Bromethylester (OEt(Br)) der Aminosauren (4) lassen sich einfach herstellen und mit Z- und Boc-Aminosauren zu Z- und Boc-Dipeptidestern 5 und 6 verknupfen. Die Esterfunktionen sind gegen nicht zu stark saure und basische Einflusse bestandig. Sie konnen mit Natriumiodid in DMF in 2-Iodethylester 8 ubergefuhrt werden, welche mit Zink in einer Eintopfreaktion spaltbar sind. Durch Umsetzung mit Trimethylamin gehen die hydrophoben 2-Halogenethylester in die hydrophilen Cholinester 10 und 11 uber. Diese sind sehr stabil gegen Sauren. Sie konnen in wasrig…
Synthesis of Processable Inorganic‐Organic Hybrid Polymers Based on Poly(silsesquioxanes): Grafting from Polymerization Using ATRP
2008
Inorganic-organic hybrid polymers have been synthesized utilizing atom transfer radical polymerization (ATRP) from a functionalized poly(methylsilsesquioxane) (PMSSQ) macroinitiator. Different polymeric ATRP initiators were prepared by co-condensation of functionalized trichlorosilanes with methyltrimethoxysilane. Various vinyl monomers have been successfully grafted from these macroinitiators, demonstrating a highly variable synthetic concept, which offers the chance to synthesize a wide spectrum of inorganic-organic hybrid polymers. All synthesized polymers were soluble in various organic solvents. Spin-coating these hybrid materials onto various substrates could produce stable and adhere…
Bitterness and astringency of flavan-3-ol monomers, dimers and trimers
1999
Intensity of astringency and bitterness of seven flavonoid compounds was evaluated by a time-intensity (TI) procedure. Eighteen trained judges rated intensity continuously from ingestion, through expectoration at 10 s until extinction of the sensation. The seven stimuli included two flavan-3-ol monomers, (+)-catechin and (−)-epicatechin, three dimers and two trimers synthesised from catechin or epicatechin by condensation with (+)-dihydroquercitin. As the degree of polymerisation increased, maximum bitterness intensity (Imax) and total duration (Ttot) decreased whereas astringency Imax increased. The monomers were significantly higher in bitterness at Imax than the dimers, which were signif…
Racemic and Optically Pure Heptahelicene-2-carboxylic Acid: Its Synthesis and Self-Assembly into Nanowire-Like Aggregates
2010
Heptahelicene-2-carboxylic acid was effectively synthesised from suitably functionalised naphthalene building blocks. Methoxy-substituted 1,1'-ethyne-1,2-diylbis(2-but-3-yn-1-ylnaphthalene) was cyclised in the presence of CpCo(CO)(2)/PPh(3) to 2-methoxy-7,8,11,12-tetrahydroheptahelicene, which was converted into heptahelicen-2-yl trifluoromethanesulfonate. This reactive intermediate underwent Pd(OAc)(2)/dppp-catalysed methoxycarbonylation reaction to provide, after hydrolysis, heptahelicene-2-carboxylic acid. The racemate was resolved into enantiomers by semipreparative HPLC on a chiral column. The helicity of (+)-(P)-heptahelicene-2-carboxylic acid was assigned by correlating its CD spectr…
Diastereoselective Functionalization of a Spherand‐Type Calixarene
1994
Condensation of 5,5'-di-tert-butyl-2,2'-dihydroxybiphenyl (1) with formaldehyde yields a cyclic trimer 2 (and tetramer 3) having three (four) methylene groups less than a calix[6]arene (calix[8]arene). Alkylation of the (flexible) trimer with ethyl bromoacetate gives exclusively the stereoisomer 4 with C 2 symmetry, while the isomer with D 3 symmetry is not observed. Two isomers 6a and 6b (C 2 and C 1 symmetry) are obtained by treatment with tert-butyl bromoacetate which both are converted by transesterification with methanol into the same hexamethyl ester 5 having C 2 symmetry. These results are rationalized by restricted rotation around Ar-Ar bonds for larger O-alkyl groups also around Ar…