II. CHEMISTRY 487 



The Kiict'cssful chomical identification of a-tocophorol l)y Fernholz^^ be- 

 gan with the isohition of (iuro(|iiinone (tetramethylhydro(iuinone) from the 

 products of its thermal decomposition. Dehj'drogenation by selenium''- also 

 })roduced it, and the British workers^" obtained traces of it from concentrates 

 alonjj; with pseudocumoqiiinone from pure /3-tocopherol. 



Fernholz's suggestion^' that a-tocopherol might be a mono ether of 

 duroquinone was shown to be untenable by them'^" and by John,^^' ^* 

 Karrer,^^ Drummond/^ and their coworkers, most of whom proposed a 

 coumaran or chroman nucleus with a side chain (Karrer) of isoprene resi- 

 dues as in phytol (the alcoholic portion of chlorophyll). Fernholz" also 

 concluded from the dissimilarities of the absorption spectra of ethers of 

 duroquinone and of tocopherol that this did not have a simple ether struc- 

 ture. Thermal decomposition of tocopherol produced not only durohydro- 

 quinone but also an unsaturated aliphatic hydrocarbon. Mild oxidation of 

 this substance by chromic acid produced a lactone, C21H40O2 , whose free 

 hydroxy acid was so readily relactonized that a tertiary hydroxyl had to 

 be postulated. More \ngorous oxidation yielded dimethylmaleic anhydride, 

 an acid C16H30O2 , along with a ketone CisHseO, diacetyl, and acetone. 

 Particularly the formation of a 16-carbon acid limited the number of pos- 

 sible structures for the lactone. After close and skillful organic chemical 

 reasoning, the structure he proposed for a-tocopherol was that of a substi- 

 tuted G-hydroxychroman, with a long aliphatic side chain attached to the 

 pyran ring. 



Intensive work in other laboratories confirmed the presence of a chroman 

 nucleus; degradation studies by John and his coworkers^^ demonstrated this 

 nucleus with two substituents on carbon 2 (adjacent to the chroman oxy- 

 gen), thus providing a tertiary ether ring and optical activity, and Smith 

 and his coworkers^^ came to the same conclusion by still different organic 

 chemical procedures and reasoning. 



Meantime, still favoring the coumaran structure, but undecided, Karrer 

 and his coworkers^" accomplished an almost quantitative condensation of 



" E. Fernholz, J. Atri. Chem. Soc. 59, 1154 (1937). 



« C. S. McArthur and E. M. Watson, Science 86, .35 (1937). 



" VV. John, E. Dietzel, and P. Glinther, Z. phijsiol. Chem. 252, 208 (19.38). 



'^ W. John, Z. physiol. Chem. 252, 222 (1938). 



35 P. Karrer, H. Salomon, and H. Fritzsche, Helv. Chim. Ada 21, 309 (19.38). 



38 A. R. Moss, W. F. J. Cuthbertson, J. F. Danielli, and J. C. Drummond, J. Soc. 



Chem. Ind. (London) Transurlioiis 57, 133 (19.38). 

 " 10. Fernholz, /. Am. Chem. Soc. 60, 700 (19.38). 



3" W. John, ]-:. Dietzel, P. Giinther, and W. lOmte, NatKrwis.senschaflcn 26, .366 (19.38). 

 " I.. I. Smith, IT. E. llngnade, and W. W. Prichard, Science 88, .37 (19.38). 

 *" P. Karrer, IT. Fritzsche, B. IT. Hingier, and TT. Salomon, Hclv. Chim. Acta 21, .520 



(19.38). 



