title: Stereodivergent and Protecting-Group-Free Synthesis of the Helicascolide Family: A Rhodium-Catalyzed Atom-Economical Lactonization Strategy.
abstract: Natural products of polyketide origin, in particular small-sized lactones often possess a very broad range of impressive biological activities. An efficient way to demonstrate the concise access to six-membered lactones was emphasized as part of a stereodivergent and protecting-group-free synthesis of all three representatives of the helicascolide family. This strategy features an atom-economical and highly diastereoselective rhodium-catalyzed "head-to-tail" lactonization by an intramolecular addition of ω-allenyl-substituted carboxylic acids to terminal allenes, including the selective construction of a new stereocenter in the newly formed core structures. The excellent selectivities with which the helicascolide precursors were obtained are remarkable, thus resulting in an expeditious and highly efficient natural product synthesis.
authors.affiliation: Institut für Organische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104, Freiburg im Breisgau, Germany.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Haydl
authors.affiliation: Institut für Organische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104, Freiburg im Breisgau, Germany.
authors.forename: Dino
authors.initials: D
authors.lastname: Berthold
authors.affiliation: Institut für Organische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104, Freiburg im Breisgau, Germany.
authors.forename: Pierre A
authors.initials: PA
authors.lastname: Spreider
authors.affiliation: Institut für Organische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104, Freiburg im Breisgau, Germany. bernhard.breit@chemie.uni-freiburg.de.
authors.forename: Bernhard
authors.identifier: 0000-0002-2514-3898
authors.initials: B
authors.lastname: Breit
mesh_terms: D001688:Biological Products / Q000138:chemical synthesis / Q000737:chemistry; D002384:Catalysis; D007783:Lactones / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D012238:Rhodium / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D001688:Biological Products; D007783:Lactones; C060395:helicascolide A; D012238:Rhodium
keywords: allenes; allylic compounds; natural products; rhodium; total synthesis