II. CHEMISTRY 571 



The two diastereoisomers tested have shown identical biological ac- 

 tivity (Table VII). 



h. Lysolecithin 



Lysolecithin, which is free from unsaturated fatty acids, has a marked 

 inhibitory elYect on the utilization of biotin by Lactobacillus casei, with a 

 molar inhibitory index of about 50,000 to 100,000. Oleic acid may counter- 

 act the inhibition caused by lysolecithin.'" If biotin functions in the 

 synthesis of oleic acid, lysolecithin might behave as a true competitive 

 analog and block the synthesis of oleic acid. This might then explain the 

 neutralizing effect of oleic acid on the inhibition caused by lysolecithin. 



i. Analog of Pimelic Acid 



€-(2.4-Dichlorosulfanilido)caproic acid, an analog of pimelic acid, in 

 which the dichlorosulfanilido group replaced one of the carboxyls of pimelic 

 acid, has been shown to inhibit the growth of several bacteria which do not 

 require biotin as a gro^^•th factor and not to affect those which do require 

 biotin. Its harmful effect may be overcome competitively by pimelic acid 

 as precursor of biotin and non-competitively by small amounts of biotin."^ 



CI 



I CI 

 NH 



I 

 COOH SO2 



I I 



(CH2)5 (CH2)6 



I 1 



COOH COOH 



Pimelic acid e(2-4-Dichlorosulf:inili(lo)" 



caproic acid 



1" W. Trager, J. Bacteriol. 56, 195 (1948). 



"8 D. W. Woolley, J. Biol. Chem. 183, 495 (1950). 



