Secondary Fatty Acids

Secondary fatty acids may differ from common fatty acids in chain length, additional fimctional groups, e.g., hydroxy and hydroperoxy groups, or other structural elements (branches in the carbon chain, presence of cyclopropane or cyclopentene rings, etc.) (D 3.2). 

Fatty acids with unusual structure occur in microorganisms, plants, and animals. 

Extension of the carbon chain, hydroxylation, peroxidation, methylation, substitution at the a-C-atom 

Alkanes, alkenes, alkanals, al kanols, esters, acetylenic compounds, eicosanoids 

Mechanisms in the synthesis and transformation of secondary fatty acids 

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A representative of a pentaacyl lipid A, in which the only secondary fatty acid present is associated with GlcN(I), is precursor lb (Fig. 9 B). This compound was isolated from a temperature-sensitive mutant of S. typhi-murium (mutant Ts5) (173). The only 3-acyloxyacyl residue in precursor lb is 14 O[3-0(16 O)], which is amide-linked to GlcN (I) (position 2). 

Lipid A contains primary fatty acids directly linked to hydroxyl and amino groups of the backbone, and secondary fatty acids bound to hydroxyl groups provided by the primary acyl residues. The number of carbon atoms of primary and secondary fatty acids is, in the majority of lipid A studied, in the range of 10 to 18. They are, in general, saturated, even-numbered, and straight-chain fatty acids and in only few cases, are unsaturated, odd-numbered, and iso- and ante-iso branched derivatives present in molar amounts. 

D 3 Acetic Acid Derivatives D 3.2.1 Secondary Fatty Acids Chemistry... 

Fig, 56. Mechanisms in the synthesis and transformation of secondary fatty acids... 

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