Chapter VII D 



PANTOTHENIC ACID 



Specificity 



Even before the complete structure of pantothenic acid was determined 

 to be D-N-(a,y-dihydroxy-/?,/?-dimethylbutyryl)-/?-alanine, preliminary 

 data indicating that the factor was an hydroxy acid conjugated with 

 ^-alanine by an amide linkage l led to the preparation of a number of 

 analogous compounds. Some of these possessed partial activity. 2-4 Subse- 

 quent to the announcement of the structure of pantothenic acid, a number 

 of more closely related analogues of the vitamin were prepared and tested 

 for activity in replacing pantothenic acid in the nutrition of organisms 

 requiring the vitamin. 



In Table 24, the specificity of pantothenic acid is indicated by com- 

 parison of its activity with that of its analogues. The activity of panto- 

 thenic acid resides only in the dextrorotatory form, which has been 

 indicated to be the D-configuration by application of Hudson's amide 

 rule. 8, 21 - 22 l-( — )-Panthothenic acid appears to be inactive for organisms 

 requiring the intact vitamin. 



The methyl and ethyl esters of pantothenic acid are comparable to the 

 vitamin in promoting the growth of rats, 6 " 9 but ethyl pantothenate is only 

 6.8 per cent as effective as pantothenic acid for Lactobacillus casei. G ' 7 



Acetylation is reported to destroy the activity of pantothenic acid in 

 natural extracts for chicks 23 and bacteria. 24 However, synthetic ethyl 

 monoacetyl D-pantothenate (Table 24) is approximately as active as 

 pantothenic acid for both rats and chicks, but is only 0.7 per cent as 

 effective as the vitamin for Lactobacillus casein 7 It is necessary to 

 hydrolyze methyl monoacetyl pantothenate to obtain maximal activity 

 with Streptococcus faecalis R. 2 Mono-p-nitrobenzoyl D-pantothenic acid 

 (N-a-p-nitrobenzoxy-y-hydroxy-/?,/?-dimethylbutyryl-/?-alanine) is inac- 

 tive for Lactobacillus casei. 7 



The analogues which replace pantothenic acid are usually only partial 

 substitutes for the vitamin in the nutrition of most organisms; however, 

 some analogues appear to be capable of completely replacing the vitamin 

 in the nutrition of some organisms. Of the analogues which appear to act 

 without prior conversion to pantothenic acid, N- (a-hydroxy-£,/?-di- 

 methylolbutyryl) -^-alanine ("hydroxypantothenic acid") and N-(a- 



620 



