title: Synthetic studies on dicyclopenta[a,d]cyclooctane terpenoids: construction of the core structure of fusicoccins and ophiobolins on the route involving a Wagner-Meerwein rearrangement.
abstract: The total diastereoselective synthesis of dicyclopenta[a,d]cyclooctane core skeleton of tricyclic terpenoids, fusicoccins, and ophiobolins is reported. The synthesis commences from 2-methylcyclopent-2-en-1-one and leads first to the easily accessible intermediary cyclopenta[8]annulene 18. The subsequent steps include two key transformations: shifting the angular methyl group from the angular to the neighboring position employing a carbocationic rearrangement (26 → 28) and construction of a quaternary stereogenic center via alkylation of α-methylcyclooctanone intermediate (38 → 48). In the context of the latter transformation, a series of model experiments on alkylation of 2-methylcyclooctan-1-one were conducted. The stereochemical assignments were verified by X-ray analyses of the key structures 39 and 50.
authors.affiliation: Institute of Organic Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Michalak
authors.forename: Karol
authors.initials: K
authors.lastname: Michalak
authors.forename: Zofia
authors.initials: Z
authors.lastname: Urbanczyk-Lipkowska
authors.forename: Jerzy
authors.initials: J
authors.lastname: Wicha
mesh_terms: D018360:Crystallography, X-Ray; D015394:Molecular Structure; D013729:Terpenes / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D013729:Terpenes