A Vinylsilane Route of (+/-)-Gymnomitrol

Article abstract of DOI:10.1021/ja00397a043

Gymnomitrol, a sesquiterpenic alcohol of unusual structure, has been synthesized in an efficient and stereoselective manner.Selective ketalization of the bicyclo<3.3.0>octanedione (4), followed by Wolf-Kishner reduction and deketalization, afforded the C_s symmetric ketone 5.Methylenation with paraformaldehyde and N-methylanilinium trifluoroacetate gave the exocyclic methylene derivative (6) which entered into copper-catalyzed 1,4 addition with the Grignard reagent from (E)-2-(bromovinyl)trimethylsilane and subsequent in situ methylation to deliver 12 in 66percent yield.Epoxidation and dilute acid hydrolysis of this intermediate furnished hydroxy ketone 15 directly.The coproducts 14a and 14b could also be converted to 15 which was oxidized to diketone 16.The final stages of the synthesis involved regioselective addition of methyllithium to 16, dehydration of the tertiary carbinol fuctionality, and ultimate lithium aluminium hydride reduction.