Tuberculostearic acid

FIGURE 8.2 Structures of two unusual fatty acids lactobacillic acid, a fatty acid coutaiuiug a cyclopropane ring, and tuberculostearic acid, a brauched-chaiu fatty acid. 

In addition to unsaturated fatty acids, several other modified fatty acids are found in nature. Microorganisms, for example, often contain branched-chain fatty acids, such as tuberculostearic acid (Figure 8.2). When these fatty acids are incorporated in membranes, the methyl group constitutes a local structural perturbation in a manner similar to the double bonds in unsaturated fatty acids (see Chapter 9). Some bacteria also synthesize fatty acids containing cyclic structures such as cyclopropane, cyclopropene, and even cyclopentane rings. 

The optically active Trogoderma -pheromones ( )- and (Z)-24have been synthesized starting from (5)-citronellol and 4-pentynoic acid [192], Alkatrienes 25, sex attractants of Lepidoptera, were prepared by mixed Kolbe electrolysis with linolenoic acid [193], 26, the pheromone of the German cockroach Blattela Germanica has been prepared from 3-methylheneicosanoic acid [194], ( ) — Tuberculostearic acid (27) has been... 

Saturated fatty acids with alkyl branching like e.g. (R,S)-tuberculostearic acid 39 are formed by olefination of 36 with ketone 37, hydrogenation of the resulting methyl 10-methyl-9-octadecenoate 38 with Raney-nickel and subsequent hydrolysis 66). 

The fatty acids found in these preparations of mycobacterial phospholipids are generally a mixture of palmitic, hexadecenoic, stearic, octadecenoic, and tuberculostearic acids. 

Vaccenic acid, c/j-CH3(CH2)5CH=CH(CH2)9COOH. 8. Corynomycolenic acid, c/J-/ C 3H27CH2CH(COOHX HOH(CH2)7CH=CHC6HIrff. 9. Tuberculostearic acid, 10 methyloctadecanoic acid. 10, Qrpl thienoic acid, CH3(CH2)7CH(CH3>CH2CH (CH3)CH==C(CH3)C00H. 11. CC, octadecanoic acid DD, 2-methyloctadecanoic acid. 12. Juvenile hormone,... 

C19H38O2 10-Mel8 0 10-Mel8 0 10-Methyloctadecanoic acid Tuberculostearic acid 1929... 

Wallace, P.A., D.E. Minnikin, K. McCrudden, and A. Pizzarello, Synthesis of (R,5)-10-Methyloctadecanoic Acid (Tuberculostearic Acid) and Key Chiral 2-Methyl Branched Intermediates, Chem. Phys. Lipids 71 145-162 (1994). 

A mid-chain branch occurs in tuberculostearic acid (lOo-methylstearic) present in the lipids of the human tubercle bacillus and in other bacterial lipids. 

Triundecanoin, 370 Tropical sprue, 528 Trout, 131,134,136 Tuberculostearic acid, 15 Tuna oil, 180... 

Additional C-atoms (see the formula of ergosterol, Fig. 120) in the side chains of certain sterols derive from the methyl group of L-methionine. When there are additional ethyl side chains, e.g., in stigmasterol and jff-sitosterol (Fig. 120), two subsequent methylations take place. One hydrogen atom of the methyl group of L-methionine is lost during the methylation (Fig. 123). The mechanism in this respect resembles that of the synthesis of tuberculostearic acid from oleic acid (D 3.2.1). 

There are alkyne fatty acids such as crepenynic acid (104 C18) and fatty acids that contain branches such as corynomycolic acid (105 C32), found in Corynebactrium diphtheriae, or tuberculostearic acid (106 C19), which is found in Mycobacterium tuberculosis. These latter organisms are responsible for diphtheria and tuberculosis, respectively. 

Protomagnamycin would have a C18 carbon skeleton very similar to that of tuberculostearic acid. 

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