title: The remarkable effect of cosolvent on a samarium(II)-mediated 4-exo-trig cyclization: further synthetic studies on pestalotiopsin A.
abstract: A samarium(II)-mediated 4-exo-trig cyclization in which a remote stereocenter serves to control the facial selectivity of the cyclization is described. The apparent coordination of a tert-butyldimethylsilyl ether to the samarium center appears to give rise to the selectivity. The remarkable effect of the cosolvent, 2,2,2-trifluoroethanol, on the cyclization of this substrate, is also discussed. A stereoselective synthesis of the general class of gamma,delta-unsaturated aldehyde cyclization substrate is reported, and the utility of the cyclization is demonstrated in an approach to the fully functionalized core of pestalotiopsin A.
authors.affiliation: Department of Chemistry, The Joseph Black Building, University of Glasgow, Glasgow, G12 8QQ Scotland, U.K.
authors.forename: David J
authors.initials: DJ
authors.lastname: Edmonds
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Muir
authors.forename: David J
authors.initials: DJ
authors.lastname: Procter
mesh_terms: D003500:Cyclization; D007202:Indicators and Reagents; D007783:Lactones / Q000737:chemistry; D015394:Molecular Structure; D012493:Samarium / Q000737:chemistry*; D012717:Sesquiterpenes / Q000138:chemical synthesis*; D012997:Solvents / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D007202:Indicators and Reagents; D007783:Lactones; D012717:Sesquiterpenes; D012997:Solvents; C430595:pestalotiopsin A; D012493:Samarium