Synthesis of a peroxime proliferator activated receptor (PPAR) alpha/gamma agonist via stereocontrolled Williamson ether synthesis and stereospecific SN2 reaction of S-2-chloro propionic acid with phenoxides

The stereospecific synthesis of the PPAR alpha/gamma agonist I was accomplished via ethylation of the optically pure tribydroxy 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 S(N)2 reaction of the phenol 4 with S-2-chloropropionic acid is best achieved via the sodium phenoxide of 4 derived from Na-0 as the reagent of choice. The structure elucidation and key purification protocols to achieve pharmaceutical purity will also be described.