Search results for "Cyclic compound"

17O NMR study of chlorinated anisoles

1988

The 17O NMR chemical shifts of anisole and all 19 chlorinated anisoles measured in CDCI3 at ambient temperature show a dispersion of approximately 40 ppm. The substituent chemical shifts (SCS) of di- or more highly chlorinated compounds cannot be reproduced by addition of single substituent effects. Theoretical calculations of the 17O NMR chemical shifts have been attempted by molecular mechanical and semi-empirical molecular orbital methods at the INDO level, but the results are not satisfactory.

Accumulation of polycyclic aromatic hydrocarbons in cultivated microalgae.

1975

Extending Limits of Chlorine Kinetic Isotope Effects

2012

Chlorine kinetic isotope effects exceeding semiclassical limits were observed in enzyme-catalyzed reactions, but their source has not been yet identified. Herein we show that unusually large chlorine kinetic isotope effects are associated with reactions in which chlorine is the central atom that is being passed between two heavy atoms. The origin of these large values is the ratio of imaginary frequencies for light-to-heavy species (the so-called temperature-independent factor).

Selective, Sensitive, and Rapid Analysis with Lateral-Flow Assays Based on Antibody-Gated Dye-Delivery Systems: The Example of Triacetone Triperoxide

2013

[EN] Antibodygated MSNs that are loaded with a rhodamine dye and that can be used for the determination of the presence of peroxide-based explosive TATP with a lateral-flow fluorescence reader have been designed and prepared, thereby allowing for detection limits in the lower ppb range. The mechanism of the detection relies on a displacement of the antibody from the surface of the hybrid material because of highly affine antibody-TATP interactions, which release a much larger number of entrapped dye molecules from the pores than antibodies are displaced. The high selectivity of the antibody is retained in the gated material, thus allowing for a remarkable discrimination against H2O2. System…

Über die Synthese von o-Acylamino-β-dimethylaminopropiophenonen Mitt.: Aminomethylierung von 2-Nitro-5-methoxy-und 2-Nitro-5-benzyloxyacetophenon

1971

Der von Makino und Takahashi sowie Joh als 2-Nitro-5-methoxy-β-dimethylamino-propiophenon bezeichnete Korper wurde als 2-Nitro-5-methoxy-α-dimethylaminomethyl-acrylophenon identifiziert. Nach einer fruher beschriebenen Methode zur Darstellung von 2-Nitro-β-dimethylamino-propiophenon war es moglich, 2-Nitro-5-methoxy- und 2-Nitro-5-benzyloxy-acetophenon normal zu aminomethylieren. –Die Synthese von 2-Amino-5-methoxy-, 2-Amino-5-benzyloxy- und 2-Amino-5-hydroxy-β-dimethylamino-propiophenon sowie ihrer Acetylderivate wird beschrieben. Synthesis of o-Acylamino-β-dimethylamino-propiophenones The compound synthetized by Makino and Takahashi and by Joh described as 2-nitro-5-methoxy-β-dimethylamin…

Using theozymes for designing transition-state analogs for the intramolecular aldol reaction of δ-diketones

2001

Two theozymes for the intramolecular aldol reaction of δ-diketones have been studied using ab initio methods. The presence of both acid/base residues favors several steps of the aldol reaction. The appropriate positioning of these residues can accelerate one of two diastereromeric reaction pathways, the catalyzed aldol reaction being highly stereoselective. Analysis of the geometrical parameters, charge distribution, and the shape of molecular electrostatic potential for the corresponding acid/base catalyzed transition structure allows us to design adequate transition-state analogs to favor a reactive channel of this intramolecular aldol reaction. © 2001 John Wiley & Sons, Inc. Int J Quant …

Stereoselective synthesis of 2-amino-1-hydroxy-3-phenylpropylphosphonic acid

1996

Abstract A highly stereoselective synthesis of 2-amino-1-hydroxy-3-phenylpropylphosphonic acid was achieved by simple addition of diethyl phosphite to enantiomeric N-blocked phenylalaninals. These compouds exhibit significant herbicidal activity.

Enantioselective Synthesis of Unsymmetrical Benzoins from (S)-Mandelic Acid Enolate and Aromatic Aldehydes.

2004

The reaction of the lithium enolate of the 1,3-dioxolan-4-one derived from optically active (S)-mandelic acid and pivalaldehyde with aromatic aldehydes proceeds readily to give the corresponding aldol products in good yields and diastereoselectivities. Subsequent hydroxyl protection, basic hydrolysis of the dioxolanone, oxidative decarboxylation of the α-hydroxyacid moiety, and hydroxyl deprotection provides chiral unsymmetrical benzoins with high enantiomeric excesses.

ChemInform Abstract: Stereoselective Synthesis of 2-Amino-1-hydroxy-3- phenylpropylphosphonic Acid.

2010

Abstract A highly stereoselective synthesis of 2-amino-1-hydroxy-3-phenylpropylphosphonic acid was achieved by simple addition of diethyl phosphite to enantiomeric N-blocked phenylalaninals. These compouds exhibit significant herbicidal activity.

Cationic mono- and bi-nuclear iron complexes as Lewis acid catalysts in Mukaiyama reactions

1992

Organometallic Lewis acids derived from photolysis of mono- and bi-nuclear cationic iron carbonyl complexes function as excellent catalysts for the Mukaiyama aldol reaction.