658 THE BIOCHEMISTRY OF B VITAMINS 



activity for certain microorganisms. 31 a-Pyracin, as judged by survival 

 of the animals on a vitamin B 6 -cleficient diet, appears to have slight 

 pyridoxine activity in mice. 46 The possibility of contamination with 

 pyridoxine was suggested, since a-pyracin is inactive for chicks. 47 



Analogues of Pyridoxal and Pyridoxamine. 2-Methyl-3-hydroxy-4- 

 hydroxymethyl-5-aminomethylpyridine, an isomer of pyridoxamine, is 

 only 0.002, 1.4, 0.22 and 0.5 per cent as active as pyridoxamine for 

 Streptococcus faecalis R, Lactobacillus casei, Saccharomyces carls- 

 bergensis, and rats, respectively. The activity for Lactobacillus casei is 

 slightly exaggerated, since it is compared with pyridoxamine, which is 

 relatively inactive as compared with pyridoxal for this organism. 31 

 2-Methyl-3-hydroxy-4-hydroxymethyl-5-formylpyridine, the correspond- 

 ing isomer of pyridoxal, is 0.005-0.01, 0.03, and 29-73 per cent as effective 

 as pyridoxal for Streptococcus faecalis R, Lactobacillus casei and Sac- 

 charomyces carlsbergensis, respectively. The 5-formyl derivative appar- 

 ently can be utilized effectively by yeast, which presumably reduces the 

 formyl group. Rats cannot effectively convert this compound to the 

 vitamin. 31 



The ethyl acetal derived from the hemiacetal of pyridoxal is 50 to 75 

 per cent as active as pyridoxal for Streptococcus faecalis R and Lacto- 

 bacillus casei and just as effective as the vitamin for Saccharomyces 

 carlsbergensis. This activity, however, is attributed to the hydrolysis of 

 the acetal. 31 



Since vitamin B G functions in transamination reactions, the biological 

 activity of Schiff bases and analogous compounds of the amino acids and 

 pyridoxal are of interest. Eighteen pyridoxylamino acids corresponding 

 to the formula indicated below have been prepared 62 and tested 63 for 



R 

 CH 2 — NH— CH— COOH 



HO— ^S— CH 2 OH 



their ability to replace the vitamin B 6 group for a variety of organisms. 

 These compounds were prepared by reductive condensation of pyridoxal 

 with the following amino acids: DL-alanine, DL-aspartic acid, L-aspar- 

 agine, DL-glutamic acid, L-glutamic acid, glycine, DL-isoleucine, dl- 

 leucine, L-leucine, L-lysine, DL-methionine, DL-norleucine, DL-phenyl- 

 alanine, DL-serine, DL-threonine, DL-tryptophan, L-tyrosine and dl- 

 valine. None of these compounds is more than 0.5 per cent as active as 

 pyridoxal hydrochloride on a weight basis for Saccharomyces carlsber- 



