title: Studies on the synthesis of the ABC rings of (+/-)-hexacyclinic acid.
abstract: A synthesis of the ABC-rings of the polyketide natural product hexacyclinic acid has been achieved. The B-ring was formed first via an intramolecular ester-tethered Diels-Alder reaction, and the A-ring was annulated to this by means of a SmI(2) mediated reductive 5-exo-trig cyclization of a samarium-ketyl radical onto a vinyl group. Finally, the C-ring was closed using olefin metathesis. Interestingly, use of enyne metathesis resulted in the synthesis of a more functionalized 5-membered C-ring in a model system, but an undesired 6-membered C-ring in the actual system. An investigation of this change in selectivity is discussed.
authors.affiliation: Department of Chemistry, University of York, Heslington, York, North Yorks YO10 5DD, UK. pac507@york.ac.uk
authors.forename: Paul A
authors.initials: PA
authors.lastname: Clarke
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Cridland
authors.forename: Gabriele A
authors.initials: GA
authors.lastname: Rolla
authors.forename: Mudassar
authors.initials: M
authors.lastname: Iqbal
authors.forename: Nigel P
authors.initials: NP
authors.lastname: Bainbridge
authors.forename: Adrian C
authors.initials: AC
authors.lastname: Whitwood
authors.forename: Claire
authors.initials: C
authors.lastname: Wilson
mesh_terms: D006576:Heterocyclic Compounds, 4 or More Rings / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure
chemical_list: D006576:Heterocyclic Compounds, 4 or More Rings; C502347:hexacyclinic acid