TERPENOIDS AND STEROIDS 



137 



Some specific compounds with their occurrence are given below. All known mem- 

 bers of this group are oxygenated at C-3 usually as alcohols but some as ketones. They 

 are distinguished from each other by unsaturations, additional hydroxyl groups, and fre- 

 quently carboxyl groups. Stereochemical differences also play an important role in this 

 group, but their consideration is beyond the scope of this book, and no configurations are 

 indicated in the accompanying formulas. The /3-amyrin type structure is most common 

 and occurs in both primitive and advanced plants. Interesting correlations between plant 

 classification and triterpenoid structures are presented by Brieskorn (16). 



COOH 



oleanolic acid (widely dis- 

 tributed, e.g. Olea europaea) 



COOH 



ursolic acid (in waxy coating 

 of many leaves and fruits, 

 e. g. Arctostaphylus uvaursi) 



/3-amyrin (resins, latex and 

 waxes of many plants, e. g. 

 Canarium commune) 



