The stereochemistry of 2- and 3-hydroxy fatty acids in a Recent lacustrine sediment

Homologous series of 2- and 3-hydroxy fatty acids occur in both the free and the bound lipid fractions of an oligotrophic lacustrine sediment (Loch Clair, N.W. Scotland). The stereochemistry of each constituent was assigned by gas chromatographic separation of diastereoisomeric O-2(S)-phenylpropionyl methyl ester derivatives. Free and bound 2-hydroxyacids above C₂₀ showed the R configuration characteristic of by-products formed during fatty acid metabolism by α-oxidation. In the C₁₄–C₁₈ region, bound 2- and 3-hydroxyacids show the R configuration more dominantly than the corresponding free lipids. These bound 2(R)- and 3(R)-hydroxyacids are attributed to microbial cell wall lipids.