Enzymatic Preparation of (S)-3-Hydroxytetradecanoic Acid and Synthesis of Unnatural Analogues of Lipid A Containing the (S)-Acid

Synthesis of unnatural analogues, that contain (S)-3-hydroxytetradecanoyl moieties in place of the corresponding natural (R)-isomers, of both lipid A and its biosynthetic precursor, designated precursor Ia or lipid IVA, has been achieved through our recently developed procedure. (S)-3-Hydroxytetradecanoic acid was prepared from its racemate through the optical resolution by the use of a lipase and subsequent fractional recrystallization. The (S)-acyl analogue of lipid A exhibited slightly stronger interleukin-6 inducing activity than the corresponding natural lipid A, and the (S)-acyl analogue of the biosynthetic precursor was far more active than the natural precursor in inhibiting the induction of interleukin-6 by lipopolysaccharide.