Chemistry of New Zealand Apiaceae: New irregular diterpenes from Anisotomeflexuosa and A-haastii showing conformational exchange

Two new derivatives of a recently-reported class of irregular diterpene hav e been discovered in New Zealand species of the Apiaceae family. 16-Acetoxy anisotomenoic acid (8) (3,3a,4,4-tetramethyl-3-{(Z)-5-acetoxy-4-methyl-3-pe ntenyl}-2,3,3a,4,5,6-hexahydro-1H-2-indenecarboxylic acid) and anisotomene- 1,12-diol (11) (3,3a,4,4-tetramethyl-3-(2-hydroxy-4-methyl-3-pentenyl)-2,3, 3a,4,5,6-hexahydro-1H-2-indenyl) methanol) have been obtained from the sub- alpine plants, Anisotome flexuosa and A. haastii respectively. C-13 nuclear magnetic resonance (n.m.r.) spectra of the anisotomene derivatives are com plicated by line broadening. Molecular modelling of anisotomenoic acid (1) and anisotomenol (2) suggests that this is due to conformational exchange i n the highly substituted bicyclo [4,3,0] non-1-ene ring system.