NATUKAl. WAXES 



347 



known that they should not be included among the sterols, as they have a 

 different structure. On selenium reduction, they give 1, 2, 8-trimethyl- 

 phenanthrene instead of Diels' hydrocarbon (CisHie) ; they apparently do 

 not contain the jS.ve-membered ring attached to phenanthrene. They are 

 now considered to be members of the triterpenes. These are products 

 composed of 30 carbon atoms whose carbon skeleton is believed to be 

 divided into isopentane units. Lanosterol and agnosterol are the only 

 triterpenes which have been prepared from an animal source^^^; one of 

 these, i.e., lanosterol, has also been separated from yeast. ^^^ The method 

 of molecular rotation differences, which has been frequently employed to 

 establish the structure of the steroids, enables one to distinguish the triter- 

 penes readily from the steroids. ^^^ Because these do not belong to the 

 sterol group, the term "isocholesterol," as well as the names lanosterol and 

 agnosterol, are misleading and should be dropped. For a further discus- 

 sion to the triterpenes see Section 2 (page 383). 



h'. Other Zoosterols: A number of other sterols, which belong to the 

 category of animal products, have been described. These include spongo- 

 steroP^"-"^ from the sponge (Suberites domunculd), as well as from the 

 similar form Suberites compacta^''^ (the so-called neospongosterol), and 

 clionasterol from the boring sponge (Cliona celata) j^^-"^^^'^^^ sterols from the 

 freshwater sponge {Spongilla lacustris) ,^^^ from the sea anemone (Anemonia 

 sulcata) ,^^'' rose coral (Manicina areolata) ,-^^ the branched coral (Xiphogorgia 

 sp.),^^^ and the crab (Limulus polyphemus) , as well as from three types of 

 sea urchins (Echinidae).^^^ Poriferasterol,^^^'"^ also, is found in sponges, 

 in association with clionasterol. On hydrogenation they yield the same 

 saturated alcohol, poriferastanol. From this fact it has been deduced that 

 poriferasterol is 22-dehydroclionasterol : 



Neospongosterol 



Clionasterol 



"•^ II. Wielaiul and W. Benend, Z. physiol. Chem., 274, 215-222 (1942). 



"3 D. n. R. Barton, /. Chem. Soc, 194-5, 813-819. 



"* F. R. Valentine and W. Bergmann, /. Org. Chem., 6, 452-461 (1941). 



2« C. A. Kind and W. Bergmann, ./. Org. Chem., 7, 341-345 (1942). 



"« A. Maztir, J. Am. Chem. Soc, 6.i, 883-884, 2442-2444 (1941). 



"7 M. DelTner, Z. physiol. Chem., 278, 105-168 (1943). 



238 W. Bergmann, M. L. McLean, and D. Lester, /. Org. Chem., 8, 271-284 (1943). 



233 A. M. Lyon and W. Bergmann, J. Org. Chem., 7, 428-431 (1942). 



