Chiral chemodiversity and its role for biological activity. Some observations from studies on insect/insect and insect/plant relationships

Many compounds occur in Nature in both enantiomeric forms. This chiral chemodiversity is common among certain classes of natural products whereas other classes of compounds usually occur in only one of the enantiomeric forms. Thus triterpenoids and steroids belong to the same enantiomeric family. On the other hand, many of the lower terpenoids (mono- sesqui-, and diterpenoids) are present in both of their enantiomeric forms. The chiral chemodiversity in relation to the biological functions of the compounds will be discussed with reference to recent results on the enantiomeric composition of monoterpenes from various natural sources. Focus will be on the role of the enantiomeric composition of alpha-pinene in the host plant, Picea abies (L.) Karst., of the spruce bark beetle, Ips typographus. Research on the biological functions of chiral compounds requires test sampled of very high enantiomeric purity. Synthetic- and analytical methods are important and our current studies on such methods are referred to.