RESUMO
Treatment of (-)-sclareol and related compounds with lead tetraacetate affords tetracyclic compounds bearing a 2,8-dioxabicyclo[5.2.0]nonane moiety with complete regio- and stereoselectivity. This process, which is also applicable to 1,5-diols with a similar substitution pattern, facilitates the development of efficient syntheses toward oxepane terpenoids, such as aplysistatin derivatives.
RESUMO
The first synthesis of spirolactone (+)-vitedoin B (14 steps, 8.0% global yield) and spiro enol ether (+)-negundoin A (19 steps, 3.7% global yield), via a nor-labdane acetoxy ester, has been achieved starting from commercial (+)-abietic acid.
Assuntos
Abietanos/química , Diterpenos/química , Diterpenos/síntese química , Espironolactona/análogos & derivados , Espironolactona/síntese química , Ciclização , Estrutura Molecular , Espironolactona/química , EstereoisomerismoRESUMO
A very efficient method for synthesizing spirolactones is reported. Treatment of δ,ε-unsaturated carboxylic acids with iodine and triphenylphosphine under mild conditions leads to the corresponding spiro γ-lactones in high yield and with complete stereoselectivity. Utilizing this, the first synthesis of the terpene spirolactones (-)-isoambreinolide, (+)-vitexifolin D and (+)-vitedoin B has been achieved.
Assuntos
Diterpenos/síntese química , Lactonas/síntese química , Compostos de Espiro/síntese química , Diterpenos/química , Lactonas/química , Conformação Molecular , Compostos de Espiro/química , EstereoisomerismoRESUMO
An efficient and stereoselective spiroannulation of unsaturated enols is reported. Unsaturated ß-dicarbonyl compounds undergo cyclization by reaction with catalytic I2-PPh3, affording the corresponding spiro enol ether derivatives, with complete regio- and stereoselectivity, under mild conditions. Utilizing this new methodology, the first total synthesis of the anti-inflammatory diterpene negundoin A and a naturally occurring trypanocidal aldehyde is reported.
Assuntos
Diterpenos/síntese química , Iodo/química , Cetonas/química , Compostos Organofosforados/química , Compostos de Espiro/síntese química , Catálise , Ciclização , Diterpenos/química , Estrutura Molecular , Compostos de Espiro/químicaRESUMO
Treatment of o-allyl phenols with catalytic NIS-PPh3 affords the corresponding spirodihydrobenzofuran derivatives in high yield with high regio- and total stereoselectivity under mild conditions. These results were utilized to achieve the first total synthesis of the protein kinase C inhibitor corallidictyal D starting from α-ionone.