title: Formal synthesis of berkelic acid: a lesson in α-alkylation chemistry.
abstract: The full details of our enantioselective formal synthesis of the biologically active natural product berkelic acid are described. The insertion of the C-18 methyl group proved challenging, with three different approaches investigated to install the correct stereochemistry. Our initial Horner-Wadsworth-Emmons/oxa-Michael approach to the berkelic acid core proved unsuccessful upon translation to the natural product itself. However, addition of a silyl enol ether to an oxonium ion, followed by a one-pot debenzylation/spiroketalisation/thermodynamic equilibration procedure, afforded the tetracyclic structure of the berkelic acid core as a single diastereoisomer.
authors.affiliation: School of Chemical Sciences, The University of Auckland, 23 Symonds Street, Auckland, New Zealand.
authors.forename: Michael C
authors.initials: MC
authors.lastname: McLeod
authors.forename: Zoe E
authors.initials: ZE
authors.lastname: Wilson
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Brimble
mesh_terms: D000478:Alkylation; D002384:Catalysis; D003300:Copper / Q000737:chemistry; D015394:Molecular Structure; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D013141:Spiro Compounds; C520589:berkelic acid; D003300:Copper