Linked Life Data

14505416

Source:http://linkedlifedata.com/resource/pubmed/id/14505416

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
39
pubmed:dateCreated
2003-9-24
pubmed:abstractText
Enol MEM ethers 4 and 15 and the corresponding enol acetates were hydrogenated over Pd/C with very high (>99%) diastereoselectivity to saturated delta-lactones. A stereochemical generalization can be formulated thus: trans-5,6-disubstituted 1-oxa-3-cyclohexen-2-ones (e.g. 14 and 15) are hydrogenated over Pd with high selectivity from the side trans to the C(6)-substituent. A mechanistic rationalization of the stereochemical outcome in the Pd-catalyzed hydrogenation of this as well as other types of substituted alpha,beta-unsaturated delta-lactones is presented. An analysis of X-ray crystallographic data for 67 compounds demonstrated a great conformational diversity of the saturated delta-lactone ring. Besides, ab initio calculations (HF/6-31G) indicated a very high conformational mobility. Thus, the lowest calculated transition state for the conversion of the half-chair, most stable, conformer of delta-valerolactone to the boat-type conformer lies only 1.93 kcal/mol above the former. Beside these two conformers, also chair, envelope and skew conformations are accessible; all lie less than 2 kcal/mol above the half-chair. The previous conformational paradigm comprising only boat and half-chair types is incomplete.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
125
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
11942-55
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2003
pubmed:articleTitle
Highly diastereoselective hydrogenations leading to beta-hydroxy delta-lactones in hydroxy-protected form. A modified view of delta-lactone conformations.
pubmed:affiliation
Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden. svante@organ.su.se
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't