II. CHEMISTRY 231 



|)ul)lishod their synthesis in which 2-methyl-4-carboxy-5-c'yano-()-pyridoiie 

 amide served as the startinji; compound. The synthesis of Szaho'*' consists 

 in oxidizing 3-metliyl-4-methoxy(iuinoline to the dicarboxyhc derivative 

 of the methoxypyridoxine. This was then converted to the dicyano com- 

 pound through intermediates. Reduction to the diamino compound followed 

 by hydrolysis of the ether and treatment with nitrous acid yielded the vita- 

 min. 



More recently applying the method developed for reducing the esters of 

 heterocyclic carboxylic acids to the corresponding hydroxymethyl com- 

 pounds, Jones and Kornfeld^^ directly reduced the 4,5-dicarboxylic ester 

 of pyridoxine to pyridoxine with lithium aluminum hydride. Excellent ^nelds 

 were obtained. By this step the complicated conversion of the carboxylic 

 groups used bj^ others was neatly overcome. 



E. SPECIFICITY 

 1. General 



Since the recognition that only a part of the vitamin Be activity of natural 

 products can be attributed to pyridoxine, vitamin Be is now used as a class 

 name to include all compounds having vitamin Be activity. On the adop- 

 tion of the report of the Committee on Biochemical Nomenclature of the 

 American Society of Biological Chemists, pyridoxine is correctly applied 

 only to the single substance, 2-methyl-3-hydroxy-4,o-di(hydroxymethyl)- 

 pyridine. The two other important naturally occurring substances with 

 vitamin Be activity are pyridoxal, 2-methyl-3-hydroxy-4-formyl-5-hydroxy- 

 methylpyridine, and pyridoxamine, 2-methyl-3-hydroxy-4-aminomethyl-5- 

 hydroxymethylpyridine. 



2. Pyridoxal and Pyridoxamine 



The existence of other forms of pyridoxine was recognized by Snell el al.^* 

 as the result of the comparison of microbiological assays on extracts of 

 natural materials with the values based on chemical and animal assay. In 

 some instances the discrepancies were as much as several thousandfold. 

 This highly active form of pyridoxine was given the trivial name, pseudo- 

 pyridoxine. When pyridoxine was treated with mild oxidizing agents, Car- 

 penter and Strong^^ observed a marked increase in activity for the micro- 

 organism Lactobacillus casei. SnelP^'^ extended his observation that 



« J. L. Szabo, U. S. Pat. 2,359,260 (1944). 



» R. G. Jones and E. C. Kornfeld, J. Am. Chem. Soc. 73, 107 (1951). 



" E. E. Snell, B. M. Guirard, and R. J. Williams, ./. Biol. Chem. 143, 519 (1942). 



« L. E. Carpenter and F. M. Strong, Arch. Biochcm. 3, 375 (1944). 



» E. E. Snell, Proc. Soc. Expl. Biol. Med. 51, 356 (1942). 



" E. E. Snell, J. Am. Chem. Snr. 66, 2082 (1944). 



» E. E. Snell, J. Biol. Chem. 154, 313 (1944). 



