title: Total synthesis and repudiation of the helianane family.
abstract: Total syntheses of two structures purported as (+)-heliananes were completed in six pots. Spectral comparisons, between the synthetic and natural compounds, revealed a misassignment of the eight-membered ring in the heliananes. The key step in the syntheses of the proposed structures and the confirmation of their actual structures was a diastereoselective inverse-demand Diels-Alder reaction between an optically active enol ether and an ortho-quinone methide species, which was generated in situ at low temperature by the sequential addition of methylmagnesium bromide and di-tert-butyl dicarbonate to a salicylaldehyde.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA.
authors.forename: Jason C
authors.initials: JC
authors.lastname: Green
authors.forename: Sandra
authors.initials: S
authors.lastname: Jiménez-Alonso
authors.forename: Eric R
authors.initials: ER
authors.lastname: Brown
authors.forename: Thomas R R
authors.initials: TR
authors.lastname: Pettus
mesh_terms: D000818:Animals; D002254:Carbonates / Q000737:chemistry; D003500:Cyclization; D045563:Indolequinones / Q000737:chemistry; D008386:Marine Biology; D015394:Molecular Structure; D011161:Porifera / Q000737:chemistry; D012717:Sesquiterpenes / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D002254:Carbonates; D045563:Indolequinones; D012717:Sesquiterpenes; C505682:helianane; C068040:quinone methide; C027600:bis(tert-butoxycarbonyl)oxide