Linked Life Data

16089458

Source:http://linkedlifedata.com/resource/pubmed/id/16089458

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
32
pubmed:dateCreated
2005-8-10
pubmed:abstractText
The effects of different amino acid catalysts and substrate substituents on the stereoselectivity of the title reactions have been studied with the aid of density functional theory methods. Experimental data available in the literature have been compiled. B3LYP/6-31G(d) calculations match the general experimental trends and provide useful insights into the origins of the variations in stereoselectivities. Acyclic primary amino acids allow a greater conformational flexibility in the aldol transition states compared with proline. This makes them poorer enantioselective catalysts with triketone substrates with a methyl ketone side chain. The steric repulsion upon substitution at the terminal methyl group increases the energy difference between anti- and syn-chairs with primary amino acid catalysts and, consequently, the stereoselectivities. Proline, in contrast, is a poor catalyst for the latter reactions because the substituent's steric bulkiness raises the activation energy of the favored C-C bond-forming pathway.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
17
pubmed:volume
127
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
11294-302
pubmed:meshHeading
pubmed:year
2005
pubmed:articleTitle
Theoretical studies of stereoselectivities of intramolecular aldol cyclizations catalyzed by amino acids.
pubmed:affiliation
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA.
pubmed:publicationType
Journal Article