Synthesis of a Peroxime Proliferator Activated Receptor (PPAR) α/γ Agonist via Stereocontrolled Williamson Ether Synthesis and Stereospecific S_N2 Reaction of <i>S</i>-2-Chloro Propionic Acid with Phenoxides

Abstract

The stereospecific synthesis of the PPAR alpha/gamma agonist 1 was accomplished via ethylation of the optically pure trihydroxy derivative 6, itself derived via an enzymatic resolution. The ethylation can be accomplished without epimerization only under strict control of the reaction conditions and the choice of base (sodium tert-amylate), temperature (-30 degrees C), order of addition, and solvent (DMF). The key diastereospecific SN2 reaction of the phenol 4 with S-2-chloropropionic acid is best achieved via the sodium phenoxide of 4 derived from Na0 as the reagent of choice. The structure elucidation and key purification protocols to achieve pharmaceutical purity will also be described.