42 FATTY ACID METABOLISM IN MICROORGANISMS 



4. POSITION OF THE CYCLOPROPANE RING IN 



LACTOBACILLIC ACID AND SEPARATION OF 



CARBON ATOM 19 FROM THE MOLECULE 



As has been mentioned previously (Chapter 1, section 2), 

 lactobacillic acid reacts readily with hydrogen bromide with 

 formation of a mixture of monobromononadecanoic acids 

 which arise from addition of the elements of hydrogen 

 bromide to the cyclopropane ring. Dihydrosterculic, dl- 

 ^r<2n5-9,10-methylene- and DL-^?fl/75-ll,12-methyleneoctadec- 

 anoic acids exhibit the same behavior (18). Four structural 

 possibilities, A, B, C, and D (Fig. 2.3), must be considered 

 for the ring opening products. However, structures C and 

 D appear to represent the most likely ones. The ring 

 opened compounds derived from the two synthetic trans 

 acids, from lactobacillic acid and from dihydrosterculic acid 

 separately were dehydrobrominated by exposure to boiling 

 collidine. In this manner each bromo acid was converted 

 into a mixture of olefinic acids which may contain some 

 or all of the components shown on Fig. 2.3. 



The crude dehydrohalogenation products from each acid 

 were then oxidized by the Lemieux procedure (19) and the 

 mixture of oxidation products separated into a neutral and 

 an acidic fraction. The latter was analyzed for its various 

 components by chromatography on buffered silica-gel col- 

 umns (20). The experimental conditions employed for 

 analysis were so selected that the dibr^sic acids could be 

 sharply separated, whereas monocarboxylic acids evolved 

 at the very beginning of the column development as a single 

 unresolved peak. The nature of the dibasic oxidation 

 products provided important insight into the position of 

 the cyclopropane ring in the original acid. As is apparent 

 from inspection of the patterns shown on Fig. 2.4, the 



