Search results for "SELECTIVITY"
showing 10 items of 1148 documents
Stereoselective synthesis of substituted tetrahydropyran rings via 6-exo and 6-endo selenoetherification
2002
Eight unsaturated alcohols were cyclized by selenoetherification in 6-exo or 6-endo manner to give substituted tetrahydropyran rings. Yields, regio- and stereoselectivities were discussed in terms of steric and electroniceffects such as Se-O interaction. For the first time examples of the use of silica gel in selenoetherification and the effect of the X - counter ion of PhSe + on the reaction course are discussed. These effects are related to the occurrence of Se-O interaction.
Regio- and stereoselectivity in the metabolism of benzo[c]phenanthrene mediated by genetically engineered V79 Chinese hamster cells expressing rat an…
1998
Regio- and stereoselective metabolism mediated by cytochrome P450 (CYP) and metabolite-dependent cytotoxicity of benzo[c]phenanthrene (B[c]Ph) and its trans-3,4-dihydrodiol, the metabolic precursor of the carcinogenic fjord-region B[c]Ph-3,4-dihydrodiol 1,2-epoxides (B[c]PhDE), were investigated with V79 Chinese hamster cells genetically engineered for three rat and six human CYP isoforms. The order of the capabilities of the CYP isoforms to metabolize B[c]Ph was as follows: h1A1>r1A1>r1A2>h1B1>h1A2>r2B1>>h2E1>h2A6>h3A4. Regardless of the species, all individual CYP isoforms preferentially catalyzed the oxidation of B[c]Ph at the 5,6-position (K-region) except human CYP1A1 and human CYP1A2,…
Stereoselective Synthesis of trans-4,5-Disubstituted Oxazolidin-2-ones by Intramolecular Conjugate Addition of N-p-Toluenesulfonyl Carbamates.
2003
p-Toluenesulfonyl carbamates (2a-d) were prepared starting from allylic alcohols (3), in which the double bond is conjugated with an electron withdrawing group. In the presence of a catalytic amount of DBU, an intramolecular cyclisation occurred, leading to trans-4,5-disubstituted oxazolidin-2-ones (1a-d) with total stereoselection, which can be precursors of syn-4-hydroxy-3-amino acids.
Synthesis of hexahydrocyclopenta[ij]isoquinolines as a new class of dopaminergic agents.
2014
In this study, we have described the synthesis of the tricyclic 1,2,3,7,8,8a-hexahydrocyclopenta [ij]isoquinoline (HCPIQ). Herein, six differently substituted 5,6-dioxygenated-7-phenyl-HCPIQs have been synthesized using a new methodology via (E)-1-styryl-THIQ by Friedel-Crafts cyclization with Eaton's reagent. Results showed that HCPIQs (3, 3a-e) displayed a moderate affinity for D1 dopamine receptors (DR) in the micromolar range, furthermore the catecholic HCPIQs 3a (NH), 3c (NCH3) and 3e (NCH2CHCH2) exhibited outstanding affinity and high selectivity towards D2 DR. Indeed, 3a, 3c and 3e showed Ki values of 29 nM, 13 nM and 18 nM, respectively, and HCPIQs 3a (NH) and 3c (NCH3) displayed a …
Disposition and Anticoagulant Activity of the Enantiomers of Phenprocoumon in Phenobarbital Pretreated Rats
1978
The purpose of this study was to assess in rats the effect of enzyme induction on the stereoselective disposition and anticoagulant activity of phenprocoumon.
A structural insight into the P1 S1 binding mode of diaminoethylphosphonic and phosphinic acids, selective inhibitors of alanine aminopeptidases
2016
Abstract N′-substituted 1,2-diaminoethylphosphonic acids and 1,2-diaminoethylphosphinic dipeptides were explored to unveil the structural context of the unexpected selectivity of these inhibitors of M1 alanine aminopeptidases (APNs) versus M17 leucine aminopeptidase (LAP). The diaminophosphonic acids were obtained via aziridines in an improved synthetic procedure that was further expanded for the phosphinic pseudodipeptide system. The inhibitory activity, measured for three M1 and one M17 metalloaminopeptidases of different sources (bacterial, human and porcine), revealed several potent compounds (e.g., K i = 65 nM of 1u for Hs APN). Two structures of an M1 representative (APN from Neisser…
3.17 Synthetically Derived Auxiliaries: Phosphorus Derivatives
2012
This chapter aims to give an overall view of chiral-pool based asymmetric synthesis of organophosphorus compounds more particularly bearing the chirality on the phosphorus atom (P-stereogenic). The enantiomerically pure organophosphorus compounds can be obtained either by resolution of the racemate or by stereoselective synthesis using particularly ephedrine or sparteine as the main chiral auxiliaries and borane as a P(III)-protecting group.
DNA-binding and in vitro cytotoxic activity of platinum(II) complexes of curcumin and caffeine
2019
Abstract Three Pt(II) complexes containing the natural ligands curcumin and caffeine, namely [Pt(curc)(PPh3)2]Cl (1), [PtCl(curc)(DMSO)] (2) (curc = deprotonated curcumin) and trans-[Pt(caffeine)Cl2(DMSO)] (3), were synthesized and fully characterized. The data obtained suggest that, for both 1 and 2, the anion of curcumin is coordinated to the platinum ion via the oxygen atoms of the β-diketonate moiety. Spectroscopic features reveal that in 2 and 3, a DMSO molecule is S-bonded to the metal centre. For 3, all data indicate a square-planar geometry formed by a 9-N bonded caffeine, two trans chloride anions and a DMSO. The three complexes undergo changes in solution upon incubation for 24 h;…
Photoelectrocatalytic oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B3 by TiO2 nanotubes
2020
In this paper, the first photoelectrocatalytic (PEC) 3-pyridinemethanol oxidation to 3-pyridinemethanal and vitamin B-3 was investigated. To meet this aim, efficient nanotube structured TiO2 on a Ti plate as a photoanode was prepared by an anodic oxidation method in ethylene glycol and characterized by XRD, SEM, and photocurrent techniques. The effect of nanotube morphology, applied potential, Na2SO4 concentration, stirring speed of solution, and pH on the reaction activity and product selectivities were investigated. The TiO2 phase of all of the anodes was mainly the anatase one. The PEC activity, the intensity of the XRD peak and the photocurrent increased by increasing the nanotube lengt…
Pyrene-benzoylthiophene Bichromophores as Selective Triplet Photosensitizers.
2006
Combination of the pyrene and benzoylthiophene units constitutes an interesting approach to design bichromophoric photosensitizers with increased intersystem crossing quantum yield and enhanced selectivity. The potential of this strategy has been illustrated in the present work by using a model photoisomerization reaction.