Diterpenoid acids from Grindelia nana

Two new norditerpenoid acids of the labdane-type (norgrindelic acids), 4,5- dehydro-6-oxo-18-norgrindelic acid (1) and 4 beta-hydroxy-6-oxo-19-norgrind elic acid (2), as well as a new grindelic acid derivative, 18-hydroxy-6-oxo grindelic acid (3), were isolated from the aerial parts of Grindelia nana, In addition, the known compounds, 6-oxogrindelic acid, grindelic acid, meth yl grindeloate, 7 alpha,8 alpha-epoxygrindelic acid, and 4 alpha-carboxygri ndelic acid were also isolated. The structures of the new compounds were ch aracterized on the basis of spectroscopic analysis.