LACTOBACILLIC ACID 11 



methyl irfl7?5-3-keto-4,5-methylenetridecanoate (XI, x = 1) 

 in the manner described for conversion of (II) into (IV). 

 Alkylation of (XI, x = 7) with methyl e-iodocaproate (XII, 

 y = 1) followed by saponification and decarboxylation yields 

 ^ra/?j-8-keto-9,10-methyleneoctadecanoic acid (XIII, x = 7), 

 which is reduced to DL-fran5-9,10-methyleneoctadecanoic 

 acid (XIV, X and y = 7). DL-^r«n5-ll,12-Methyleneoctadec- 

 anoic acid (XIV, x = 5, y = 9) is obtained from trans-2,S- 

 methylenenonanoic acid (VII, x = 5) by the same sequence 

 of reactions, with methyl n-iodocaprylate (XII, y = 9) serv- 

 ing as the alkylating reagent. 



Comparison of the infrared absorption spectra of the 

 highly purified synthetic acids with the spectrum of lacto- 

 bacillic acid (Fig. 1.7) shows that the positions and intensi- 

 ties of the major absorption bands are identical. Especially 

 noteworthy is the presence in all of the spectra of a sharp 

 absorption band at 9.8 ^, which is characteristic of the cyclo- 

 propane ring. These findings, coupled with the chemical 

 behavior of the synthetic acids (stability to oxidation and 

 lability to hydrogenolysis with formation of nonadecanoic 

 acid), provide convincing evidence for the proposed gen- 

 eral architecture of lactobacillic acid. However, neither of 

 the synthetic products is identical with lactobacillic acid 

 from which they differ with respect to melting point, melt- 

 ing point of the amides, and most importantly as concerns 

 the x-ray diffraction pattern (Table 1.2). 



DL-d5-9,10-Methyleneoctadecanoic acid (dihydrosterculic 

 acid) is an analog of lactobacillic acid which deserves par- 

 ticular attention. Its chemical behavior and infrared ab- 

 sorption spectrum are essentially identical with those of 

 lactobacillic acid. 



Dihydrosterculic acid is obtained when sterculic acid, a 

 constituent of the seed fat of the tropical tree Sterculia 



