NATTTRAL WAXES 



349 



other pliytosterols are found in this oil. Biirian-^" discovered it in wheat 

 germ and rye germ oil. However, the original sitosterol was shown by 

 Anderson and co-workers^**' -^^'^^^ to consist of at least three isomeric 

 forms, which they designated as a, jS, and 7. Some dihj-drositosterol has 

 also been shown to be present in wheat germ oil. More recent studies 

 have indicated that the a-form, which is the most soluble fraction, consists 

 of at least three isomers, ^^'-^^^ which are designated ai, 012, and 0:3. The 

 constants of some of these sitosterols are given in Table 6. 



The tetracyclic nucleus has been shown to be the same in sitosterols and 

 in cholesterol; therefore, the variation must be in the side chain. ^^^ How- 

 ever, the a-sitosterols apparently have a second double bond on Cg which 

 may be in ring B or C. Bernstein and Wallis-^^ have suggested the follow- 

 ing structure for ai-sitosterol. Presumably, ao and as are essentially the 

 same, with some shifts in the position of the double bond on Cg: 



ai-SitosteroI 



A number of workers have proved that jS-sitosterol is actually 22-dihydro- 

 stigmasterol.*""^^^ It is now believed that 7-sitosterol is a stereoisomer of 

 j3-sitosterol and that they differ only in the configuration on the C24 atom. 



Fieser and Fieser^^^ suggest that an important center of asymmetry of 

 the sterols exists on C24 for those products with side chains in that position. 

 They point out that in addition to the relationship of /S- and 7-sitosterol, a 

 corresponding similarity exists between campesterol and ergostanol (22,23- 



250 R. Buridn, Monatsh., IS, 551-574 (1897). Reprinted in Sitzber. Akcul. Wiss. Wien, 

 Math, nalurw. Klasse, Abt. lib, 106, 549-572 (1897). 



251 R. J. Anderson and R. L. Shriner, J. Am. Chem. Soc, 48, 2976-2986 (1926). 



=" R. J. Anderson, R. L. Shriner, and G. O. Burr, /. .4m. Chem. Soc, 48, 2987-2996 

 (1926). 



253 E. S. Wallis and E. Fernholz, ,/. Am. Chem. Soc, 58, 2446-2449 (1936). 

 25* S. Bernstein and E. S. Wallis, /. Am. Chem.. Soc, 61, 1903-1904 (1939). 



255 L. Ruzicka and E. Eichenberger, Helv. Chim. Acta, 18, 430-434 (1935). 



256 S. Bernstein and E. S. Wallis, J. Am. Chem. Soc, 61, 2308-2313 (1939). 



257 B. E. Bengtsson, Z. physiol. Chem.., 237, 46-51 (1935). 



258 R. E. Marker and E. L. Whittle, J. Am. Chem. Soc, 59, 2704-2708 (1937). 



259 S. Bernstein and E. S. Wallis, J. Org. Chem., 2, 341-344 (1937). 



