Search results for "Organic Chemical"

Enantioselective transport of amino acid through supported chiral liquid membranes

1993

Abstract Two chiral alcohols, nopol and (2S)-(−)-methyl-1-butanol, immobilized in the pores of a polyethylene film were used for the anantioselective transport of amino acid hydrochloride. The degree of stereoselectivity of the permeation process varied from 0.39 to 1.52 depending on both the type of the chiral membrane phase and the properties of the amino acid. The evaluation of the membrane ability to separate stereoisomers was performed by the step-by-step analysis by considering the effect of amino acids' hydrophobicity, polarity and degree of chirality. For the purpose of this paper, the chirality measure was introduced. It was demonstrated that the enantioselectivity was affected mai…

Stereoselective glycosylation of Alcohols and Silyl Ethers Using Glycosyl Fluorides and Boron Trifluoride Etherate

1985

The stereoselective glycosylation of alcohols and their silyl ethers has been achieved using O-alkyl-, O-acyl-, and acetal-protected glycosyl fluorides of the pyranose and furanose series and boron trifluoride etherate in CH2Cl2.

Divergent reactivity of nucleophilic 1-bora-7a-azaindenide anions

2017

The reactions of 1-bora-7a-azaindenide anions, prepared in moderate to excellent yields by reduction of the appropriate 1-bora-7a-azaindenyl chlorides with KC8 in THF, with alkyl halides and carbon dioxide were studied. With alkyl halides (CH2Cl2, CH3I and BrCH(D)CH(D)tBu), the anions behave as boron anions, alkylating the boron centre via a classic SN2 mechanism. This was established with DFT methods and via experiments utilizing the neo-hexyl stereoprobe BrCH(D)CH(D)tBu. These reactions were in part driven by a re-aromatization of the six membered pyridyl ring upon formation of the product. Conversely, in the reaction of the 1-bora-7a-azaindenide anions with CO2, a novel carboxylation of …

REDOX PROPERTIES ARE CONSERVED IN RUBISCOS FROM DIATOMS AND GREEN ALGAE THROUGH A DIFFERENT PATTERN OF CYSTEINES1

2010

Eukaryotic RUBISCO appears in two sequence-diverging forms, known as red-like (present in nongreen algae) and green-like (of green algae and higher plants) types. Oxidation of cysteines from green-like RUBISCOs is known to result in conformational changes that inactivate the enzyme and render a relaxed structure more prone to proteolytic attack. These changes may have regulatory value for green algae and higher plants, promoting RUBISCO catabolism under stress conditions. We compare here red-like RUBISCOs from several diatoms with a representative green-like RUBISCO from Chlamydomonas reinhardtii, paying special attention to the cysteine-dependent redox properties. Purified diatom RUBISCO p…

Thieme Chemistry Journals Awardees – Where Are They Now? Molybdenum(V)-Mediated Synthesis of Nonsymmetric Diaryl and Aryl Alkyl Chalcogenides

2017

Oxidative chalcogenation reaction using molybdenum(V) reagents provides fast access to a wide range of nonsymmetric aryl sulfides and selenides. The established protocol is tolerated by a variety of labile functions, protecting groups, and aromatic heterocycles. In particular, when labile moieties are present, the use of molybdenum(V) reagents provides superior yields compared to other oxidants.

Titanium (IV) chloride complexes with salen ligands supported on magnesium carrier: Synthesis and use in ethylene polymerization

2009

The magnesium support with the formula MgCl 2 (THF) 0.32 (Et 2 AlCl) 0.36 was used for immobilization of salen complexes of titanium [Ti(salen)Cl 2 , Ti(salen(O-Me) 2 )Cl 2 ]. The effects of the catalyst composition (i.e. type of titanium complex and type of activator), polymerization temperature, polymerization time, and the effect of comonomer (1-octene) on the activity of the obtained supported catalysts, on the polymer characteristics (molecular weight, molecular weight distribution, melting point), and on the polymer morphology were studied. The findings were compared to those obtained for corresponding unsupported systems. Catalysts immobilization results in considerable changes in ca…

Reaction of 2-acetyltetralone with some esters of benzoic acid

1986

In order to investigate the pharmacological screening of a number of pyran-4-ones their synthesis by cyclization with sulphuric acid of the corresponding 1,3,5-triketones has been carried out with high yields. In the course of preparation of the latter the reaction of 2-acetyltetralone with some esters of benzoic acid derivatives has been studied and in particular, for a number of them, an interesting nucleophilic substitution of a chlorine atom with an alkoxy group on a benzenic nucleus has been evidenced.

Cholesterol protein interaction - the issue of specificity

2009

ChemInform Abstract: Reaction of 2-Acetyltetralone with Some Esters of Benzoic Acid.

1987

In order to investigate the pharmacological screening of a number of pyran-4-ones their synthesis by cyclization with sulphuric acid of the corresponding 1,3,5-triketones has been carried out with high yields. In the course of preparation of the latter the reaction of 2-acetyltetralone with some esters of benzoic acid derivatives has been studied and in particular, for a number of them, an interesting nucleophilic substitution of a chlorine atom with an alkoxy group on a benzenic nucleus has been evidenced.

Difference in the behavior of methyl (S)-?-bromopropionate in its addition to trimethylvinylsilane depending on the method of initiation

1996

The addition of methyl (S)-2-bromopropionate to trimethylvinylsilane initiated by systems based on iron pentacarbonyl affords a racemic adduct and is accompanied by racemization of the unreacted chiral ester. In the presence of benzoyl peroxide, the reaction proceeds similarly, but no racemization of the starting chiral ester occurs.