STRUCT UKE OF THE K VITAMINS 835 



only in the 2,3 positions, since the aromatic portion of the naphthoquinone 

 is shown to have no side chains attached. 



The position of the side chains was determined by Binkley el al}^ on the 

 basis of the products obtained by mild oxidation with chromic acid. Un- 

 der such treatment, 2-methyl-l,4-naphthoquinone-3-acetic acid was iso- 

 lated (VI) ; this was identified by comparing it with the same product pre- 

 pared synthetically.^^ An analogous reaction was obtained by chromic 

 acid oxidation of the diacetate of dihydrovitamin Ki. The end product in 

 this case, as determined by comparison with the synthetic methyl ester, is 

 l,4:-diacetoxy-2-methylnaphthalene-3-acetic acid (VII).'' 



o 



• W 



H O-CCH, 



^/'\/%. // 



r,o HC C CCH,C-OH 



HC. /C XCH3 



C C 



0-CCH. 

 // * 

 



3ZII 

 Oxidation of Dihydrovitamin Ki with Chromic Acid 



The nature of the side chain was readily elucidated as the result of the 

 hydrogenation and the identification of the products of ozonolysis of di- 

 hydrovitamin Ki diacetate. It was shown that, as a result of hydrogena- 

 tion, 4 molecules of hydrogen were taken up. Since only 3 molecules can 

 be absorbed in the saturation of the naphthoquinone and conversion to the 

 naphthohydroquinone, it was indicated that there is one double bond in the 

 side chain. The location of the double bond in the side chain, and the na- 

 ture of the side chain, were deduced by the isolation of a ketone, CisHssO, 

 on oxidation of the diacetate of dihydrovitamin Ki. This was found to be 

 identical with the ketone formed when phytol is oxidized,^' which is 2,6,10- 

 trimethylpentadecan-14-one (VIII). Further indication of the structure 

 of the side chain and position of attachment to the naphthoquinone nucleus 

 was obtained by the demonstration of the simultaneous formation of 1,4- 

 diacetoxy-2-methylnaphthalene-3-acetaldehyde (IX), which Binkley ei 

 alP-^'^"^ characterized from its semicarbazone. This compound can be iso- 

 lated when the product formed following ozonolysis of dihydrovitamin Ki 

 diacetate in glacial acetic acid is decomposed by zinc in ether. These reac- 

 tion products definitely establish vitamin Ki as 2-methyl-3-phytyl-l,4- 

 naphthoquinone . 



" F. G. Fischer and K. Lowenberg, Ann., 464, 69-90 (1928). 



" S. B. Binkley, R. W. McKee, S. A. Thayer, and E. A. Doisy, /. Biol. Chem., 133, 

 xii-xiii (1940). 



