PANTOTHENIC ACID 625 



inhibitory analogue of pantothenic acid for lactic acid bacteria. Kuhn, 

 Wieland, and Moller 45 independently and almost simultaneously re- 

 ported similar findings. Barnett and Robinson 15 prepared, and Mc- 

 Ilwain 46 tested the same analogue independently, but published their 

 results at a later date with the suggestion of the name "pantoyltaurine" 

 for the analogue. The term "pantoyl" for the a,y-dihydroxy-/?,/3-dimethyl- 

 butyryl radical, as suggested by Mcllwain, 46 has since been widely used. 

 The two optically active forms of pantoyltaurine have been prepared 

 from d- ( — ) - and l- ( + ) -pantolactone by fusion with the sodium salt 

 of taurine at 120° C for five hours. The resulting product from the l- 

 pantolactone was only about one-tenth as active as that from the lactone 

 of D-configuration. 44 If milder conditions were employed for the con- 

 densation and the products carefully purified by chromatography and 

 conversion to the quinine salt, the differential in activity was even 

 greater, about 32-fold. 45 Since the lactone intermediates were not op- 

 tically pure and since the reactions are such that some racemization takes 

 place, it seems probable that only the d-( + ) form of pantoyltaurine 

 corresponding to the configuration of the active form of pantothenic acid 

 exerts a bacteriostatic activity. This specificity of configuration has sub- 

 sequently been confirmed with other analogues of pantothenic acid. 



Table 25. Pantoyltaurine. 



As indicated in Table 25, pantoyltaurine inhibits the growth of a wide 

 variety of microorganisms which require pantothenic acid for growth. 

 The growth inhibition is counteracted specifically by pantothenic acid, 

 and becomes apparent only when the ratio of analogue to pantothenic 

 acid surpasses a critical value. The minimum ratio necessary for max- 

 imum inhibition of growth, the inhibition index, is indicated in this table. 

 This competitive relationship exists for each of the organisms over wide 

 ranges in concentration. Inhibition indices vary with time of incubation, 

 composition of the medium, size of inoculum, strain of the organism, etc. 

 Consequently, the values indicated in Table 25 are only approximate, 

 since the results from different laboratories do not agree exactly. 



