title: Formal synthesis of (+/-)-guanacastepene A.
abstract: A 17 step synthesis of 55, a late intermediate in Danishefsky's guanacastepene A synthesis, has been completed in 4% overall yield. Key features include the use of vinylmagnesium bromide in the Pd-catalyzed coupling with triflate 13 to give triene 16 without the formation of Heck products, a novel extension of the Stork-Jung vinylsilane Robinson annulation that provides tricyclic 2-hydroxymethylcyclohexenone 42 from 23b in four steps and 51% yield, the ability to obtain almost exclusively alpha'-alkylation of 35ba by the proper choice of protecting groups, and the ability to obtain the desired beta-alcohol selectively by reduction of keto alcohol 42 rather than keto ester 53.
authors.affiliation: Department of Chemistry MS 015, Brandeis University, Waltham, Massachusetts 02454-9110, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Shi
authors.forename: Natalie A
authors.initials: NA
authors.lastname: Hawryluk
authors.forename: Barry B
authors.initials: BB
authors.lastname: Snider
mesh_terms: D000900:Anti-Bacterial Agents / Q000138:chemical synthesis*; D002384:Catalysis; D020650:Combinatorial Chemistry Techniques; D004224:Diterpenes / Q000032:analysis / Q000138:chemical synthesis*; D005658:Fungi / Q000737:chemistry*; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D013237:Stereoisomerism
chemical_list: D000900:Anti-Bacterial Agents; D004224:Diterpenes; C409194:guanacastepene