396 



VITAMIN K GROUP 



E. SPECIFICITY 



In contrast to the history of most other vitamins, synthesis of vitamin Ki 

 did not prove to be the ultimate goal in the search for antihemorrhagic 

 vitamins. Immediately after the report on phthiocol,^^ a number of com- 

 munications appeared on tests of other naphthoquinones, mostly based 

 upon rapid curative assays which may be done in a few hours. Ansbacher 

 and Fernholz^^ confirmed the activity of phthiocol and indicated an even 



240 



360 



280 320 



Wavelength, itim 

 Fig. 3. Ultraviolet absorption spectrum of synthetic vitamin Ki . (From Ewing 

 ei al.^^) 



higher potency for 2-methyl-l,4-naphthoquinone than reported by Alm- 



quist and Klose^^ or Thayer et al}^ Ultimately, this compound was reported 



to have a greater activity than vitamin Ki, by two to three times.^^- ^5-52 



Methylnaphthohydroquinone was equally as active as its oxidized 



" H. J. Almquist and A. A. Klose, Proc. Soc. Exptl. Biol. Med. 45, 55 (1940). 



« S. Ansbacher, /. Biol. Chem. 133, iii (1940). 



« F. P. Dann, Proc. Soc. Exptl. Biol. Med. 42, 663 (1939). 



" A. D. Emmett, R. A. Brown, and O. Kamm, /. Biol. Chem. 132, 467 (1940). 



<9 E. Fernholz and S. Ansbacher, Science 90, 215 (1939). 



60 S. A. Thayer, R. W. McKee, S. B. Binkley, and E. A. Doisy, Proc. Soc. Exptl. 



Biol. Med. 44, 585 (1940). 

 " H. Dam, J. Glavind, and P. Karrer, Helv. Chini. Acta 33, 224 (1940). 

 62 L. F. Fieser, M. Tishler, and W. L. Sampson, J. Biol. Chem. 137, 659 (1941). 



