THE TOCOPHEROLS 



ral tocopherols. In tliis process, heat-labile tocopherols are distilled without 

 destruction at relatively low temperature and pressure, and under condi- 

 tions of very short thermal exposure. Concentrates of 14 to 18 % tocopherols 

 are readily obtained from soybean oil'^ and also from leaf meal extracts.-" 

 Further processing permits even greater cont^entration of tocopherols.-^"'* 



CH3 



I 



HO-C^ C-H 



CH3-C%^ ,./C-OH 



CH3 



Tnmethylhydrociuinone 



+ 



HO ^CH CH3 CH3 CH3 



C-CH2-CH2-CH2-C*H-CHj-CHo-CH2-C*H-CH2-CH2-CH.-CH-CH3 



CH3 



Phytol 



CH3 

 I H2 



cx c 



HO-C^^C^ ^CH, CH3 CH3 CH 



CHa 



C ^O^ \ 

 I CH3 



CH3 



Racemic a-Tocopherol 

 Fig. 1. Synthesis of a-tocopherol. The asterisks indicate points of as.ymmetry 

 giving rise to a mixture of isomers. The natural occurring form is r/-a-tocopherol. 



2. Synthetic Tocopherols 



Condensation of trimethyl hydroquinone and phytol under the condi- 

 tions shown in Fig. 1 is conveniently carried out with almost quantitative 

 yields of racemic a-tocopherol.-^ This and similar reactions used commer- 

 cially are modifications of Karrer's and of Smith's classic original synthesis 

 in 1938.26-28 



13 F. W. Quackenbush, H. Gottlieb, and H. Steenbock, Ind. Emj. Chem. 33, 1276 

 (1941). 



20 M. E. Wall, hid. Eng. Chem. 41, 1465 (1949). 



21 K. C. D. Hickman, Chem. Eng. News 20, 1561 (1942). 



22 T. R. Olive, Chem. & Met. Eng. 51, 100 (1944). 



23 W. S. Singleton and A. E. Bailey, Oil & Soap 21, 157 (1944). 



24 J. Green and P. R. Watt, J. Sci. Food Agr. 1, 157 (1950). 



25 F. von. Werder, U.S. Pat. 2,230,970 (Feb. 4, 1941). 



2" P. Karrer, H. Fritszche, B. H. Ringier, and H. Salomon, Heh'. Chim. Acta 21, 

 520, 820 (1938). 



27 P. Karrer, II. Fritsche, B. H. Ringier, and li. Salomon, Nature, 141, 1057 (1938). 



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



