title: Syntheses of Combretastatins D-1, D-2, and D-4 via Ring Contraction by Flash Vacuum Pyrolysis.
abstract: We report the syntheses of combretastatins D-2 and D-4 as well as a formal synthesis of combretastatin D-1 by a conceptually new route harnessing a ring-contracting flash vacuum pyrolytic extrusion of sulfur dioxide from the respective 16-membered sulfone precursors. Via flash vacuum pyrolysis, even metaparacyclophanes as small and strained as the hitherto unknown oxa[1.5]metaparacyclophane could be prepared as a side product en route to combretastatin D-2 by synchronous extrusion of SO2and CO2.
authors.forename: Marina
authors.initials: M
authors.lastname: Harras
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Milius
authors.affiliation: EaStCHEM School of Chemistry, University of St. Andrews , North Haugh, St. Andrews, Fife KY16 9ST, United Kingdom.
authors.forename: R Alan
authors.initials: RA
authors.lastname: Aitken
authors.forename: Rainer
authors.identifier: 0000-0002-8413-4342
authors.initials: R
authors.lastname: Schobert