نتایج جستجو برای: stereoselectivity

تعداد نتایج: 1551  

Journal: :Chemical communications 2004
Xin Liu Ethan Sternberg David Dolphin

The first application of olefin cross-metathesis with vinylchlorins and vinylporphyrins using a "second generation" Grubbs' catalyst is reported. Cross-metathesis products were obtained in good yields with high E-stereoselectivity.

Journal: :Organic & biomolecular chemistry 2006
Dominique Harakat Jens Pesch Sinisa Marinković Norbert Hoffmann

The efficiency of the photoinduced radical addition of tertiary amines to olefinic double bonds is significantly enhanced and the stereoselectivity is influenced when thiocarbonyl compounds are added to the reaction mixture.

Journal: :Chemical communications 2007
Anders Palmelund Eddie L Myers Lik Ren Tai Steve Tisserand Craig P Butts Varinder K Aggarwal

Dienes have been formed with good stereoselectivity and in good yield from simple aldehydes and acrylates/acrylonitrile in the presence of a phosphine and a Lewis acid through a modification of the Morita reaction.

Journal: :Chemical communications 2015
Vikas Dwivedi Madala Hari Babu Ruchir Kant Maddi Sridhar Reddy

A highly general palladium catalysed regioselective hydroalkynylation of ynamides for versatile enamide building blocks with an alkyne tether is achieved with an N-substitution dependent stereoselectivity switch under very mild reaction conditions.

Journal: :Bioorganic & medicinal chemistry letters 2000
C M Hill F Wu T C Cheng J J DeFrank F M Raushel

The enzyme OPAA hydrolyzes p-nitrophenyl phosphotriesters bearing substituents at the phosphorus center ranging in size from methyl to phenyl. The enzyme exhibits stereoselectivity toward the hydrolysis of chiral substrates with a preference for the Sp enantiomer.

Journal: :Journal of natural products 2003
Veronica Armstrong Alejandro F Barrero Enrique J Alvarez-Manzaneda Manuel Cortés Beatriz Sepúlveda

An efficient and highly stereoselective synthesis of cytotoxic 8-epipuupehedione (1b) was achieved starting from natural (-)-drimenol (6). The key step to obtain stereoselectivity was the simultaneous demethylation and oxidation of the dihydrobenzopyran methoxy derivatives 10a and 10b.

Journal: :Chemical communications 2010
Yinhua Huang Sumod A Pullarkat Yongxin Li Pak-Hing Leung

Chiral tertiary phosphines were synthesized by asymmetric hydrophosphination of aromatic enones catalyzed by an organopalladium complex with high yields and stereoselectivity. The procedure offers practical access to chiral tertiary phosphines.

Journal: :Chemical communications 2009
Francisco Sarabia Samy Chammaa Miguel García-Castro Francisca Martín-Gálvez

A new type of chiral sulfur ylides has been synthesized and their reactivities against carbonyl compounds tested, showing a high degree of stereoselectivity in the formation of trans epoxy amides under very mild reaction conditions.

Journal: :Organic & biomolecular chemistry 2007
Stephen G Davies Paul M Roberts Andrew D Smith

The efficiency and stereoselectivity of the conjugate addition of lithium (Z)- or (E)-beta-amino ester enolates, generated by lithium amide conjugate addition to an alpha,beta-unsaturated ester or deprotonation of a beta-amino ester, respectively, to a range of alpha,beta-unsaturated acceptors has been investigated. Deprotonation of a beta-amino ester with LDA, followed by conjugate addition to...

Journal: :Advances in experimental medicine and biology 2001
C H Lin C C Lin

In conclusion, either enzymatic or chemical approaches have their unique features and unavoidable disadvantages. Enzyme-catalyzed sialylations provide the desired sialo-glycosidic linkages in the two enzyme reactions (CMP-NeuAc synthetase and sialyltransferase) with exclusive stereoselectivity and high yield as long as the required sialyltransferase is available. High substrate specificity of t...

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