ANALOGUES 



Thus, acetylated pyridoxine was fully active on rats, as it also 

 was on the mould, Ceratostomella ulma,^ the bacteria, S. faecalis,^ L. 

 helveticus ^ and Streptobacterium plantarum,^ on the yeast, Saccharo- 

 myces oviformis * and on excised tomato roots. ^ The 3-m ethyl, 

 4-methyl and 4-ethyl ethers had only about 10 % of the activity of 

 pyridoxine for rats,^ and little or no activity on tomato roots, bac- 

 teria 2» 3 or yeast.* The 4-methyl ether had anti- vitamin properties 

 (page 345). 



Replacement of the 4-hydroxy group of pyridoxine by a hydrogen 

 atom to give 3-hydroxy-5-hydroxymethyl-2 : 4-dimethyl-pyridine, com- 

 pletely destroyed the activity for rats/' ^ for Streptobacterium plan- 

 tarum ^ and for yeast.* The product, known as desoxypyridoxine, 

 had anti- vitamin properties (page 345). Replacement of both alco- 

 holic hydroxy groups to give 3-hydroxy-2 : 4 : 5-trimethyl-pyridine also 

 destroyed the activity for rats ^' ^ and S. plantarum.^ 



3-Amino-5-aminomethyl-4-hydroxymethyl-pyridine was inactive for 

 rats,^ whilst 3-amino-5-aminomethyl-4-methoxymethyl-2-methyl-pyri- 

 dine and 3-hydroxy-2-methyl-4 : 5-methylenediox5nTiethylpyridine were 

 inactive for micro-organisms.^ The methiodide of pyridoxine, and 

 N-methylpyridoxine betaine : 



CH2OH 

 -o/^jCHaOH 



CH3 



were inactive for rats,"^ bacteria and yeasts. ^ 



The complex formed between pyridoxine and boric acid was said 

 to be as active for rats as the vitamin itself.^ 



Isomers and Homologues 



" Isopyridoxine ", 2 : 5-bis-hydroxymethyl-3-hydroxy-4-methyl- 

 pyridine was inactive for rats and only slightly active for S. plantanwi.^ 



By a series of reactions analogous to that used in the synthesis of 

 pyridoxine, S. A. Harris and A. N. Wilson ^ prepared the pyridoxine 

 homologue, 2-ethyl-3-hydroxy-4 : 5-bis-hydroxymethylpyridine hydro- 

 chloride and found that it had only i/200th of the activity of pyri- 

 doxine in vitamin Bg-deficient rats. The compound was as active as 

 pyridoxine on tomato roots, however.^ 



Pyridoxal and Pyridoxamine 



As already stated (page 312), pyridoxal and pyridoxamine have a 

 greater growth-promoting activity than pyridoxine on the bacteria, 



343 



