Linked Life Data

15202887

Source:http://linkedlifedata.com/resource/pubmed/id/15202887

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
13
pubmed:dateCreated
2004-6-18
pubmed:abstractText
In connection with a total synthesis of cephalotaxine (1a), we have examined the addition of various nucleophilic reagents to [ABC] subunits 2 and 7 possessing a pyrrolobenzazepine core. In fact, this reaction implicates invariably the carbonyl group of 2. Regarding the reaction of 7 with nucleophiles, the most striking aspect is the complete lack of reactivity of the enaminonitrile moiety. For instance, the condensation of 7 with methylmagnesium bromide involves exclusively the cleavage of the dioxole ring, yielding regioisomers 9 and 10. With the aim of understanding the unexpected reactivity of 2 and 7 toward nucleophiles, crystallographic studies of 2 and 7 and an experimental electron density determination of 7 were carried out. The marked reactivity of the carbonyl group of 2 was interpreted by invoking the weakness of the amide resonance, due to a pronounced delocalization of the N(9) lone pair over the enaminonitrile moiety. The electron density study of 7 reveals this electron delocalization along the enaminonitrile fragment, highlighted and quantified through the bond geometries, topological indicators, and atomic charges, a phenomenon that is responsible for the failure of the addition of nucleophilic species.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0022-3263
pubmed:author
pubmed:issnType
Print
pubmed:day
25
pubmed:volume
69
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
4336-50
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2004
pubmed:articleTitle
Crystallographic/experimental electron density characterizations and reactions with nucleophiles of beta-enaminonitriles possessing a pyrrolobenzazepine core.
pubmed:affiliation
Laboratoires BIOCIS (UMR 8076), PPB (UMR 8612), and Cristallographie Bio-inorganique, Faculté de Pharmacie, Université Paris-Sud, 5, rue Jean-Baptiste Clément, 92296 Châtenay-Malabry, France.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't