852 X. THE VITAMIN K GROUP 



cal potency, because they are able to change in vivo to their corresponding 

 naphthoquinones or to their physiologically equivalent naphthohydroquin- 

 ones. A summary of the present experimental data on compounds of this 

 class is given in Table 7. 



TABLE 7 

 Biological Activity of Naphthoquinone Oxides and Comparison in Potency 



WITH Unoxidized Forms" 



Effective Effective dose 



dose, of unoxidized 



Compound pg. form, /ig." 



Vitamin Ki oxide''''' 

 2-IMothyl-l,4-naphthoquinone oxide* 

 2,3-Dimethyl-l,4-nai)lith()quiiu)iie Gxide'"'" 

 2-Methyl-3-cinnamyl-l,4-naphth()quinone oxide''''' 

 2-Phytyl-l,4-naphthoquinonc oxide'''" 

 2-Farnesyl-l,4-naphthoquinone oxide •* 

 2,7-Dimethyl- 1 ,4-naphth()(juinone oxide** 



° Adapted from H. R. Rosenberg, Chemistni and Physiology of the Vitamins, Intersci- 

 ence, New York, 1945, p. 498. 



' L. F. Fieser, M. Tishler, and W. L. Sampson, /. Am. Chem. Soc, 62, 996, 1628-1629 

 (1940). 



<= M. Tishler, L. F. Fieser, and N. L. Wendler, J. Am. Chem. Soc, 62, 2866-2871 (1940). 



<* L. F. Fieser, W. P. Campbell, E. M. Fry, and iM. D. Gates, J. Am. Chem. Soc., 61, 

 2559, 3216-3223 (1939). 



Vitamin Ki oxide (XXIII) has a biological activity almost equal to that 

 of its unoxidized form. In addition it is much more stable to light*^ than 

 is unoxidized vitamin Ki. It may occur naturally.^" Fieser et al.^^ sug- 

 gest the ready transformation of vitamin Ki oxide to the reduced naphtho- 

 hydroquinone (XXH^) by the accompanying reaction. ^-^ This form of 



,^ OH 



H II H I 



HCf C CA(^39 HC' C '■( 



O 



i\;; jj^^s^ 



HC. .0, c{ HC. C .0^ 



VV\h3 VV\h3 



oxide is similar to the group of epoxides of the vitamins A and the caroten- 

 oids which have been extensively studied by the Karrer group. Just as the 

 epoxides of vitamin A exhibit an antixerophthalmic effect, similarly the 

 vitamin K oxides are antihemorrhagic. For a discussion of epoxides, see 

 Chapter VL 



On the other hand, 2-methyl-l,4-naphthoquinone oxide falls far short in 



8« E. Fernholz, S. Ansbacher, and M. L. Moore, J. Am. Chem. Soc, 61, 1613-1614 

 (1939). 



