TRTTERPENES 391 



cussed iindor liydrocarhons. Tlio /3-amyrin group includes oleanolic acid, 

 quillaic acid, a-boswellic acid, and a number of other members indicated in 

 Figure 1. The third group is the a-amyrin group which incUides ursohc 

 acid^'^^ and j8-bos\velhc acid.'""^ The fourth group is centered on the mono- 

 hydric terpene hipeol''^^; this grouj) also includes betulin. The elemi 

 acids, along with agnol (agnosterol), cryptol (cryptosterol), and lanol 

 (lanosterol), form the last group. ^•■'^■^*'''^****" The /3- and a-amyrin groups, 

 as well as luteol, are pentacyclic, while the elemi acids contain a tetracyclic 

 group. 



The proposed structurc^^" of the |3-amyrin group is indicated by the struc- 

 tural formula for oleanolic acid, which has been strongly supported by 

 Ruzicka et al.^^^^^^'^ The formula for a-amyrin closely resembles that of 

 /3-amyrin, but probably it is not merely a stereoisomer. However, both 

 a- and j8-amyrin give the same product on dehydrogenation with sele- 

 nium. ^•'^•'^^ Lupeol has the structure indicated here: 



Oleanolic acid (a /3-amyria) 



386 J. A. Goodson, /. Chem. Soc, 1938, 999-1001. 



3«7 L. Ruzicka and W. Wirz, Helv. Chim. Acta, 22, 948-951 (1939). 



»«* L. Ruzicka and M. Brenner, Helv. Chim. Acta, 22, 1523-1528 (1939). 



^9 L. Ruzicka, R. Denss, and O. Jeger, Helv. Chim. Acta, 28, 759-766 (1945). 



^^^ H. Schulze, Z. physiol. Chem., 238, 35-53 (1936). 



390 R. D. Haworth, Ann. Repts Progress Chem., Chem. Soc. London, 34, 327-342 

 (1937). 



»9i L. Ruzicka, F. C. Van dor Sluvs-Veer, and O. Jeger, Helv. Chim. Acta, 26, 280-288 

 (1943). 



392 L. Ruzicka, O. Jeger, and W. Ingold, Helv. Chim. Acta, 26, 2278-2282 (1943). 



3" O. Brunner, H. Hofer, and R. Stein, Monatsh., 61, 293-298 (1932). 



«< F. S. Spring and T. Vickerstaff, J. Chem. Soc, 1937, 249-252. 



