Chemistry of New Zealand Apiaceae: New irregular diterpenes from Anisotome flexuosa and A. haastii showing conformational exchange

Two new derivatives of a recently-reported class of irregular diterpene have been discovered in New Zealand species of the Apiaceae family. 16-Acetoxyanisotomenoic acid (8) (3,3a,4,4-tetramethyl-3-{(Z)-5-acetoxy-4-methyl-3-pentenyl}-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. 13 C nuclear magnetic esonance (n.m.r.) spectra of the anisotomene derivatives are complicated by line broadening. Molecular modelling of anisotomenoic acid (1) and anisotomenol (2) suggests that this is due to conformational exchange in the highly substituted bicyclo [4,3,0] non-1-ene ring system.