CLASSIFICATION AND STRUCTURE OF FATTY ACIDS 35 



Lesuk, and Anderson/''^ it has a probable empirical formula of C88H176O4. 

 It occurs not only in the human tubercle bacilli •''^ but also in the bovine 

 type.^''^ These mycolic acids were found to have molecular weights of 

 1284 and 1200, respectively; they are both slightly dextrorotatory ([a]^^ 

 = 1.8°), and melt at 54-o6°C\ On heating to 300-350°C. under reduced 

 pressure, n-hexacosanoic acid distills off in both cases. 



There are also three avian mycolic acids, isolated from avian tubercle 

 wax.^^"'^^' On pyrolysis, the a-acid decomposes to a branched-chain 

 pentacosanoic acid, while the /S-variety gives rise to a normal tetracosanoic 

 acid. The third type of avian mycolic acid, 7-mycolic acid, isolated by 

 Anderson, Creighton, and Peck'''^ on pyrolysis at 270-280°C., yielded a 

 tetracosanoic acid which, however, differed in crystalline form from the 

 ordinary straight-chain fatty acid. In a more recent study, Lesuk and 

 Anderson'^'- prepared a hydroxynormy colic acid, after demethylation with 

 hydrogen iodide, which splits in a normal manner, on pyrolysis, to n-hexa- 

 cosanoic acid. Since a small amount of a hydro xy-acid having an ap- 

 proximate formula of C104H208O3 was separated from the hydroxynor- 

 mycolic and normycolic acids, it is believed that mycolic acid is a 

 mixture of two acids. That further revisions in our ideas on the mycolic 

 acids must be expected is indicated by the recent report of Stallberg-Sten- 

 hagen and Stenhagen'^^ in which it is stated that the pentacosanoic and 

 tetracosanoic acids, reported as pyrolysis products of a- and jS-mycolic 

 acids, respectively, are in actuality mixtures of closely related normal chain 

 homologues. 



e. Mycocerosic Acid. In addition to dextrorotatory acids analogous 

 to phthioic acid and the weakly levorotatory tuberculostearic acid, 

 Ginger and Anderson^^* have recently isolated a strongly levorotatory acid, 

 which they call mycocerosic acid, from the ether-soluble lead salt fraction of 

 tubercle wax. This appears to be a constant constituent of all wax frac- 

 tions of human tubercle bacilli. It is a non-crystalline waxy solid, melt- 

 ing at 27-28°C., with a levorotation {\a\^ = —5 to —6° (in chloroform)), 

 and a composition indicated by the formula, CsoHeoOs. The relatively 

 low melting point indicates that this is probably a branched-chain acid. 



f. Phytomonic Acid. Velick and Anderson ^^^ have described another 

 similar acid from the acetone-soluble fat and from the phosphatide of the 



i« F. H. Stodola, A. Lesuk, and R. J. Anderson, /. Biol. Chem., 126, 505-513 (1938). 

 »« J. Cason and R. J. Anderson, /. Biol. Chem., 126, 527-541 (1938). 

 150 R. J. Anderson and M. M. Creighton, /. Biol. Chem., 129, 57-63 (1939). 

 1" R. J. Anderson, M. M. Creighton, and R. L. Peck, /. Biol. Chem., 133, 675-693 

 (1940). 



>" A. Lesuk and R. J. -Anderson, /. Biol. Chem., 136, 603-613 (1940). 



1" S. Stallberg-Stenhagen and E. Stenhagen, /. Biol. Chem., 165, 599-604 (1946). 



1" L. G. Ginger and R. J. Anderson, J. Biol. Chem., 157, 203-211 (1945). 



i« S. F. Velick and R. J. Anderson, .7. BioL Chem., 152, 523-531 (1944). 



