Biomedical subjects

T Lectka

Publications and source records attributed to T Lectka.

7 recordsLinked to original sources

PubMed2001

Asymmetric catalysis on sequentially-linked columns.

We report a catalytic asymmetric reaction process that involves the use of solid-phase reagents and catalysts that constitute the packing of a series of "reaction columns". This process was applied to the catalytic asymmetric synthesis of beta-lactams, to yield pure products with excellent enantio- and diastereoselectivity. We have identified several advantages to conducting chemical reactions on sequential columns, including ease of catalyst and reagent recovery and simplified purification steps that preclude the need for chromatography.

Catalysis↗

PubMed2001

Reactive ketenes through a carbonate/amine shuttle deprotonation strategy: catalytic, enantioselective alpha-bromination of acid chlorides.

[reaction: see text] We have developed an efficient methodology for the generation of ketenes by employing a catalytic shuttle base and potassium carbonate as a stoichiometric base. We have applied this technology to the catalytic, asymmetric alpha-bromination of acid chlorides.

Journal Article↗

PubMed2001

Catalytic, asymmetric alpha-halogenation.

Explore the source record for details and available documents.

Catalysis↗

PubMed2000

Column asymmetric catalysis for beta-lactam synthesis.

[structure] A catalytic asymmetric reaction process was designed involving the use of solid-phase reagents and catalysts that constitute the packing of a series of "reaction columns". This process was applied to the catalytic asymmetric synthesis of beta-lactams, yielding pure product after crystallization with exceptional enantio- and diastereoselectivity.

Anti-Bacterial Agents↗

PubMed2000

Synthetic catalysis of amide isomerization.

Rotation about the C-N bond in amides can be catalyzed by Bronsted and Lewis acids, as well as nucleophiles and bases. Catalysis of amide isomerization occurs in biological systems via "rotamase" enzymes; however, the mechanisms by which these proteins operate are not completely understood. We outline investigations that provide experimental support for mechanisms believed to be feasible for the catalysis of amide isomerization and present practical applications that have resulted from this work.

Amides↗

PubMed1999

Nucleophilic metal complexes as acylation catalysts: solvent-dependent "switch" mechanisms leading to the first catalyzed Staudinger reaction.

[formula: see text] Catalytic acylation using complex transition metal salts MCo(CO)4 is demonstrated. Surprisingly, a solvent-dependent mechanistic "switch" results in a Lewis acid-based acylation mechanism in nonpolar media and a nucleophilic mechanism in polar organic media. These observations lead to the first example of a catalyzed Staudinger reaction to form beta-lactams.

Acylation↗

PubMed1999

Intramolecular acid-catalyzed amide isomerization in aqueous solution.

[reaction: see text] We report for the first time that stoichiometric and even catalytic quantities of weak acids in aqueous solution can very efficiently catalyze amide isomerization in a carefully designed system in which a proton donor is situated so that intramolecular hydrogen bonding to the amide nitrogen is highly favored. Our results provide the first experimental verification that hydrogen bond donation to the amide nitrogen by charged proton donors may play a very significant role in the enzymatic catalysis of amide isomerization.

Amides↗