Asymmetric Synthesis of Saturated Hydroxy Fatty Acids and Fatty Acid Esters of Hydroxy Fatty Acids

The recent discovery of a novel class of endogenous lipids, named Fatty Acid esters of Hydroxy Fatty Acids (FAHFAs), that present antidiabetic and anti-inflammatory activities, has attracted the interest on hydroxy fatty acids (HFAs) and their derivatives. We present herein the development of a convenient and general methodology for the asymmetric synthesis of HFAs and FAHFAs. The enantioselective organocatalytic synthesis of asymmetric terminal epoxides starting from monoprotected alpha,omega-diols and their subsequent ring opening by a Grignard reagent are the key-steps for our methodology, allowing the introduction of the hydroxy group at different positions of the long chain by proper selection of the starting diol and the Grignard reagent. MacMillan's third generation imidazolidinone organocatalyst has been employed for the epoxide formation, ensuring products in high enantiomeric purity. Furthermore, an approach for the synthesis of deuterated HFAs and FAHFAs was developed, leading to deuterated derivatives, which can be useful in biological studies and in mass spectrometry studies as internal standards.