Formal synthesis of (+/-)-guanacastepene A.
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.
Shi
Bo
B
Department of Chemistry MS 015, Brandeis University, Waltham, Massachusetts 02454-9110, USA.
Hawryluk
Natalie A
NA
Snider
Barry B
BB
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
D000900:Anti-Bacterial Agents; D004224:Diterpenes; C409194:guanacastepene