22 FATTY ACID METABOLISM IN MICROORGANISMS 



sterculic acid (28) and dl-c/j-9, 10-methylenehexadecanoic 

 acid (29) from oleic and palmitoleic acids, respectively. 



In Table 1.3, certain physical properties of both the cis 

 and trans forms of synthetic racemic 9,10- and 11,12-methyl- 

 eneoctadecanoic acids are compared with corresponding 

 properties of lactobacillic and dihydrosterculic acids, dl- 

 aVll,12-Methyleneoctadecanoic acid is similar to, but not 

 identical with, lactobacillic acid. The infrared absorption 

 spectra of the synthetic cis acids match those of lactobacillic 

 and dihydrosterculic acids. 



4. X-RAY STUDIES OF CYCLOPROPANE FATTY 

 ACIDS 



Extensive x-ray crystallographic studies by Jeffrey et al. 

 (30-32), using the above mentioned four synthetic racemic 

 cyclopropane fatty acids, i.e., dl-c/^- and trans-9,l0-methyl- 

 eneoctadecanoic and DL-m- and ^?flrz5-ll,12-methyleneocta- 

 decanoic acids, established the detailed stereochemistry of 

 these molecules and contributed materially toward solution 

 of the structure of lactobacillic acid. Two dimensional 

 Fourier projections of DL-<:/5-ll,12-methyleneoctadecanoic 

 acid (left) and DL-^rfln5-9,10-methyleneoctadecanoic acid 

 (right) (Fig. 1.12) illustrate the striking difference in the 

 shape of the cis and trans series of acids. The outstanding 

 feature of the stereochemistry of the cis acids is the boomer- 

 ang-like shape of the molecules with the bend about the 

 cyclopropane ring. This is in marked contrast to the gen- 

 erally straight chain geometry of the trans acid. The ar- 

 rangement of the molecules follows the head to head and 

 tail to tail pattern, which is a characteristic feature of the 

 crystal structure of long-chain fatty acids. Molecules of the 



