II. CHEMISTRY 395 



McKee et al.~^ stated that vitamin Ko was a 2,3-substituted naphthoqui- 

 none with six double bonds in the side groups. It would take up 9 molecules 

 of hydrogen, 3 for the naphthoquinone portion. Iodine absorption indicated 

 6 molecules of halogen taken up by non-aromatic unsaturated bonds. Upon 

 oxidation vitamin K2 yielded the same quinone acid (or aldehyde) and 

 phthalic acid that had been obtained from Ki (Binkley et al.^^). The vitamin 

 K2 was, evidently, similar to Ki, but with a much longer side chain at posi- 

 tion 3. Fragments of the side chain were isolated and identified as acetone 

 and levulinaldehyde in a mole ratio of 1 : 5 per mole of K2. This aldehyde is 

 also obtainable from the oxidation of farnesol. A structural formula was 

 proposed having two farnesyl groups linked together to form a long side 

 chain at position 3 (Fig. 1). The empirical formula was given as C41H66O2. 



D. SYNTHESIS 



Synthesis of vitamin Ki was accomplished by simple procedures. It was 

 evident that a phytyl side chain would account for the difference in molec- 

 ular weight between the methylnaphthoquinone and vitamin Ki. 2-Methyl- 

 3-phytyl-l ,4-naphthoquinone was synthesized by Almquist and Klose*" by 

 coupling methylnaphthoquinone with phytyl bromide in petroleum ether 

 and glacial acetic acid in contact with zinc dust. The product was refined 

 in a molecular still. It exhibited color, oily form, color reaction, carbon 

 and hydrogen analysis, and biological potency very similar to those of 

 vitamin Ki. 



Doisy and coworkers*^ submitted a report of synthesis of the same com- 

 pound by condensing phytyl bromide with the monosodium salt of 2- 

 methyl-l,4-naphthohydroquinone in benzene, and by direct coupling of 

 phytol and methylnaphthoquinone with zinc chloride. Details of these 

 methods were given later.^" Fieser''^ carried out the synthesis of this com- 

 pound by condensation of phytol with methylnaphthoquinone in dioxane 

 with oxalic acid as catalyst. These preliminary reports appeared in the 

 same issue of the same journal. Synthesis of vitamin K2 has not yet been 

 accomplished. 



The ultraviolet absorption of synthetic vitamin Ki was identified with 

 that of the natural vitamin'^ (Fig. 3). 



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



721 (1940). 

 « H. J. Almquist and A. A. Klose, /. Am. Chem. Soc. 61, 2557 (1939); /. Biol. Chem. 



132, 469 (1940). 

 " S. B. Binkley, L. C. Cheney, W. F. Holcomb, R. W. McKee, S. A. Thayer, D. W. 



MacCorquodale, and E. Doisy, /. Am. Chem. Soc. 61, 2558 (1939). 

 " L. F. Fieser, /. Am. Chem. Soc. 61, 2559 (1939). 



