title: A ring contraction strategy toward a diastereoselective total synthesis of (+)-bakkenolide A.
abstract: A diastereoselective route to (+)-bakkenolide A is presented from the readily available optically active Wieland-Miescher ketone. This novel synthesis of this sesquiterpene lactone features the following as key stereoselective transformations: (i) the ring contraction reaction of a octalone mediated by thallium(III) nitrate (TTN); (ii) a hydrogenation to create the cis-fused junction; and (iii) the formation of the C7 quaternary center through an enolate intermediate. Furthermore, during this work, the absolute configuration of a trinorsesquiterpene isolated from Senecio humillimus was assigned.
authors.affiliation: Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, CP 26077, CEP 05513-970 São Paulo SP, Brazil.
authors.forename: Vânia M T
authors.initials: VM
authors.lastname: Carneiro
authors.forename: Helena M C
authors.initials: HM
authors.lastname: Ferraz
authors.forename: Tiago O
authors.initials: TO
authors.lastname: Vieira
authors.forename: Eloisa E
authors.initials: EE
authors.lastname: Ishikawa
authors.forename: Luiz F
authors.initials: LF
authors.lastname: Silva
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D000970:Antineoplastic Agents / Q000138:chemical synthesis*; D006865:Hydrogenation; D007306:Insecticides / Q000138:chemical synthesis*; D007659:Ketones / Q000737:chemistry; D008968:Molecular Conformation; D015394:Molecular Structure; D012674:Senecio / Q000737:chemistry; D012717:Sesquiterpenes / Q000302:isolation & purification; D013141:Spiro Compounds / Q000737:chemistry; D013237:Stereoisomerism; D013793:Thallium / Q000737:chemistry
chemical_list: D000970:Antineoplastic Agents; D007306:Insecticides; D007659:Ketones; D012717:Sesquiterpenes; D013141:Spiro Compounds; D013793:Thallium; C042172:thallium nitrate; D015107:4-Butyrolactone; C016257:bakkenolide A