ESMOND E. SNELL 



439 



100 



MILLIMICROGRAMS PYRIDOX AL PER 6ML 



0.2 04 0.6 0.8 1.0 



I I I 1 I 



0.4 0.8 1.2 1.6 2.0 



MICROGRAMS NEOPYRITHIAMINE PER 6 ML. 



Figure 3. Comparative growth promoting action of pyridoxal and neo- 

 pyrithiamine for S. carlsbergensis 4228. 



inhibited by small amounts of thiamin and that this inhibition is over- 

 come by small amounts of vitamin Be. In many other organisms the 

 growth-promoting effects of thiamin can be counteracted by the anti- 

 vitamins, pyrithiamine (46) or neopyrithiamine (43). These products are 

 antivitamins which are so closely related in structure to thiamin (see 

 the accompanying formulas) that although they cannot duplicate the 

 physiological function of the latter they do interfere with these functions 

 in a competitive manner. It was therefore of interest to determine what 

 effect neopyrithiamine would have on an organism for which thiamin 

 was a growth inhibitor. Here too, the product counteracted the effect 

 of thiamin, that is, it promoted growth of S. carlsbergensis (Fig. 3) in 

 the same way as did pyridoxal (25). 



CH, 



N^ NH. 



^^C=C-CH2CH20H 



CHf ^C— S 



H 



Thiomin 



CH 



f 



NH, 



CH, CH.CH OH 

 I 3 / 2 2 



CH, 



+ X=C, 



ICH 



H H 

 Neopyrithiamine 



