688 XI. VITAMINS E (tocopherols) 



an artifact; this was sho"\\ai to be 5-methyl-tocol or e-tocopherol.^ By an 

 extension of the chromatographic procedure to a two-dimensional separa- 

 tion, Green et at} not only confirmed the existence of e-tocopherol, but 

 also identified a new member of the group, f-tocopherol, in many natural 

 oils; this compound was shown to have properties identical with those of 

 5,7-dimethyl-tocol, which had previously been synthesized by Karrer and 

 Fritzsche,^^ as well as by Bergel et al.,^'' and which is, in fact, this compound. 



According to Green et al.,^ the biopotency of e-tocopherol would be 

 expected to approximate that of /^-tocopherol, because of the similarity in 

 structure. Jacob, Sutchffe, and Todd^^ reported that the synthetic 5,7- 

 dimethyl-tocol, or natural f-tocopherol, has a biologic activity almost 

 equivalent to that of a-tocopherol. 



The structural relationships of the tocopherols were worked out by 

 Fernholz'*^'^" who demonstrated that they possessed a chroman ring with 

 one, two or three substituted methyl groups. Karrer and associates'^ ~^^ 

 first accomplished the synthesis of DL-a-tocopherol hi 1938, and their 

 work Avas later confirmed by Smith, Ungnade, and Pritchard.'* Baxter 

 and co-workers'' and Robeson'^ succeeded in crystallizing the natural to- 

 copherols, a and 7, but they were unable to prepare crystalline /3-tocopherol 

 except in the form of the allophanate. For a more extensive discussion of 

 the structure of the tocopherols, the reader is referred to pages 804-809 

 of The Lipids, Vol. I. The synthesis is discussed on pages 809-811, and 

 the properties are described on pages 812-819 of the same volume. Ex- 

 tensive reviews of the physiology of vitamin E include those of Evans,''' 

 of Mattill,'* and of Mason,'^ while Smith^" is the author of an excellent 



« P. Karrer and H. Fritzsche, Helv. Chim. Acta, 22, 260-263 (19.39). 



« F. Bergel, A. M. Copping, A. Jacob, A. R. Todd, and T. S. Work, J. Chein. Soc, 

 1938, 1382-1383. 



« A. Jacob, F. K. Sutcliffe, and A. R. Todd, ./. Chem. Soc, 1940, 327-332. 



" E. Fernholz, J. Am. Chem. Soc, 59, 1154-1155 (1937). 



60 E. Fernholz, /. Am. Chem. Soc, 60, 700-705 (1938). 



" P. Karrer, H. Fritzsche, B. H. Ringier, and H. Salomon, Nature, I4I, 1057 (1938). 



6* P. Karrer, H. Fritzsche, B. H. Ringier, and H. Salomon, Helv. Chim. Acta, 21, 520- 

 525(1938). 



63 P. Karrer, H. Fritzsche, B. H. Ringier, and H. Salomon, Helv. Chim. Acta, 21, 820- 

 825 f 1938) 



" L. I. Smith, H. E. Ungnade, and W. W. Prichard, Science, 88, 37-38 (1938). 



66 J. G. Baxter, C. D. Robeson, J. D. Taylor, and R. W. Lehman, /. Am. Chem. Soc, 

 (55,918-924 (1943). 



66 C. D. Robeson, J. Am. Chem. Soc, 65, 1060 (1943). 



67 H. M. Evans, J. Am. Med. Assoc, 09, 409-476 (1932). 



68 H. A. Mattill, J. Am. Med. Aswc, 110, 1831-1837 (1938). 

 68 K. E. Mason, Vitamins and Hormones, 2, 107-153 (1944). 

 «• L. I. Smith, Chem. Revs., 27, 287-329 (1940). 



