OLASSIFICATIOX AND STRI'CTURE OF FATTY ACIDS 41 



acetic acids containing 16 or 18 carbon atoms were likewise found to be 

 the most effective of this series against B. leprae. ^^°' ^^^ 



The introduction of a second ring into the aliphatic chain was found to 

 have no effect in increasing the antibacterial activity. Davies and 

 Adams ^^^ investigated this point by studying the effectiveness against B. 

 leprae of several difcyclohexjdalk}^) -acetic acids which they had synthe- 

 sized. 



The position of the carlioxyl group is of secondary importance in es- 

 tablishing the antibacterial potency insofar as the cyclic acids are con- 

 cerned. ^^* However, in a series of non-cyclic hexadecanoic and octadecan- 

 oic acids synthesized by Stanley, Jay, and Adams, ^^^ in which the position 

 of the carboxyl group varied from the end of the molecule to the center, the 

 location of the acid group was found to be of primary importance. Maxi- 

 mum activity obtained when the carboxyl group was in the middle of the 

 molecule, while no activit}^ was noted when it occupied a terminal position. 

 These results indicated that a ring is not essential for antibacterial action 

 but that the configuration of the acid has the greater importance. 



As is the case with the cyclic acids, it has been found that molecular 

 weight plays an important role with the non-cyclic acids. In the earlier 

 work ^^* it was shown that the hexadecanoic acids were somewhat more ef- 

 fective than the octadecanoic acids. Armendt and Adams^^^ reported 

 that the dialkylacetic acids containing only 12 carbons were completely 

 inactive as bactericidal agents while the C13 and Cu acids were only slightly 

 effective. Corresponding C15 and Cn acids were found to be less effective 

 in this respect than was Cie, while the C19 was less potent than the C18 

 acid. ^^^ These data emphasize the importance of the molecular weight as a 

 determining factor in conferring potency against the leprosy bacillus. 



The presence of an ethylenic linkage in the aliphatic side chain does not 

 influence the biological activity of the acids. It is recalled that the satura- 

 tion of the double bond in the pentenyl ring of chaulmoogric acid had little 

 effect upon its ability to destroy B. leprae. Bro^^Tling, Woodrow, and 

 Adams ^^''' have investigated a number of such compounds synthesized by 

 them and have reported an activity similar to that of saturated compounds 

 of the same molecular weight. The series studied by them included un- 

 decenyl alkylacetic acids, a, jS-unsaturated dialkylacetic acids, and alkyl 

 alkylacetic acids. 



'92 L. A. Davies and R. Adams, /. Am. Chem. Soc, 50, 2297-2298 (1928). 

 '93 R. Adams, W. M. Stanley, S. G. Ford, and W. R. Peterson, J. Am. Chem. Soc, 49, 

 2934-2940 (1929). 



'9< W. M. Stanley, M. S. Jay, and R. Adams, J. Ain. Chem. Soc, 51, 1261-1266 (1929). 



195 B. F. Armendt and R. Adams, J. Am. Chem. Soc, 52, 1289-1291 (1930). 



196 V. M. Greer and R. Adams, J. Am. Chem. Soc, 52, 2540-2543 (1930). 



'97 E. ]iro\vning, H. W. Woodrow, and R. Adams, J. Am. Chem. Soc, 52, 1281-1283 

 (1930). 



