494 V. CHEMISTRY OF PHOSPHATIDES AND CEREBROSIDES 



acid, CH3(CH2)7COOH, and a dicarboxylic acid with 14 carbons, presum- 

 ably COOH(CH2)i2COOH, were obtained. This would indicate that the 

 oxidation product of cerebronic acid must have been tricosanic rather than 

 tetracosanic (lignoceric) acid. If the product had been hgnoceric acid, 

 then the second product must necessarily have been a C15 dicarboxylic acid. 



The most cogent proof that cerebronic acid is a-hydroxylignoceric acid 

 is the fact that Klenk*^^ succeeded in reducing it to lignoceric acid. Al- 

 though the figures in the elementary analyses favor the C25 formula, it is 

 believed that this may be related to the presence of small amounts of 

 anhydride which would give values somewhat too high.^^^ 



(6) Properties. Cerebronic acid is a white crystalline powder, insoluble 

 in water, but soluble in ether, pyridine, warm alcohol, and acetone. When 

 the alcoholic solutions are cooled, cerebronic acid precipitates in more or 

 less oval forms which can be recognized by their fine radiating stripes^^^; 

 these sometimes appear yellow, according to Thierf elder and Klenk.*-^^^ 

 The crystals occur in two forms, ^^^ which Thudichum'^^ designated as 

 wart-like and cauliflower-type. Cerebronic acid appears under the polariz- 

 ing microscope as a conglomerate of irregular spherocrystals which give the 

 same selenite plate reaction as does phrenosine. 



Various melting points have been reported for this acid. These range 

 from values as high as 130°C.433 to values as low as 81 °C., 436.451.452 ^^yie 

 Levene and Jacobs''^^ and Rosenheim^*^ have both reported 108°C. How- 

 ever, Thierfelder and Klenk* state with emphasis that the cerebronic acid 

 obtained in their laboratory from the hydrolysis of pure phrenosine, as well 

 as from a cerebroside mixture, always shows dextro-rotation and melts at 

 100-101 °C. Moreover, cerebronic acid prepared by saturation of hydroxy- 

 nervonic acid also has the same melting point.^^^ 



Cerebronic acid contains an asymmetric carbon atom in the a-position 

 and so would be expected to exhibit optical activity. Most investigators 

 have obtained specific rotations of -f3° to +4° in pyridine, although some 

 of the low-melting samples failed to show any appreciable optical activity. 

 On the other hand, cerebronic acid exhibits a levo-rotation when dissolved 

 in chloroform. Some of these values are included in Table 12. 



On oxidation, tricosanic acid is obtained,*^^ while on reduction with 

 hydriodic acid in acetic acid, hgnoceric acid melting at 81-8L5°C. is 

 formed. ^^'^ Levene and Jacobs,^^^ as well as Levene and West,*^^ obtained 

 hydrocarbons with melting points of 53-54°C., on more drastic reduction 

 with hydriodic acid. 



Derivatives of cerebronic acid include the sodium salt, the sodium salt of 

 acetylcerebronic acid, and the methyl ester (m.p., 65°C.), all of which can 

 be crystallized from hot alcohol. ^^'^■^^ Lithium cerebronate precipitates 



«i P. A. Levene and C. J. West, J. Biol. Chcm., U, 257-265 (1913). 

 «2 r. A. Levene and C. J. West, J. Biol. Chem., 26, 115-120 (1916). 



