Pyrethrins are a group of naturally occurring insecticidal substances found in the flowers of various plants of the chrysanthemum family. The following is the structure of a typical pyrethrin, cinerin I (exclusive of stereochemistry):

(a) Locate any isoprene units present in cinerin I.
(b) Hydrolysis of cinerin I gives an optically active carboxylic acid, ()-chrysanthemic acid. Ozonolysis of (+)-chrysanthemic acid, followed by oxidation, gives acetone and an optically active dicarboxylic acid, (-)-caronic acid (C7H10O4). What is the structure of (-)-caronic acid? Are the two carboxyl groups cis or trans to each other?
What does this information tell you about the structure of (-)-chrysanthemic acid?