170081-05-7Relevant articles and documents
Total synthesis of (+)-grindelic acid by stereocontrolled oxonium ion activated pinacol ring expansion. Chemical proof of the absolute configuration of all grindelane diterpenes
Paquette, Leo A.,Wang, Hui-Ling
, p. 6005 - 6008 (1995)
(+)-Grindelic acid, synthesized enantioselectively from the levorotatory Wieland-Miescher ketone and (-)-linalool and necessarily formulated as 1a, is shown to be antipodal to the major diterpenoid of Grindelia species.
Stereocontrolled synthesis of ent-grindelic acid. A useful example of diastereofacial guidance in an oxonium ion-initiated pinacolic ring expansion
Paquette, Leo A.,Wang, Hui-Ling
, p. 5352 - 5357 (2007/10/03)
An enantioselective synthesis of (+)-grindelic acid is described, confirming that the dextrorotatory enantiomer is antipodal to the natural diterpenoid. The optically pure bicyclic ketone 5 representing the AB ring system is constructed from the levorotatory Wieland-Miescher ketone and must therefore possess the absolute configuration shown. Coupling of 5 with the 5-lithio derivative of optically active 2,3-dihydrofuran 3 derived from (R)-(-)-linalool was effected for the purpose of realizing acid-catalyzed rearrangement with generation of the appropriate spirocyclic framework. This key step is highly stereocontrolled, leading predominantly to 7. Once the advanced intermediate 15 is available in this fashion, its subsequent exposure to oxidation and dehydration steps led to the target molecule. The synthesis demonstrates unequivocally that natural (-)-grindelic acid is a true labdane diterpenoid.
