β-Oxidation of most fatty acids occurs in the mitochondria. However, β-oxidation for ω-3 polyunsaturatedfatty acids (PUFAs) is distinct from abundant fatty acids and occurs in the peroxisomes. Since little is known about peroxisomal β-oxidation, here we report the synthesis of proposed intermediates of ω-3 PUFA β-oxidation steps in free fatty acid form having a conjugated double bond, a β-hydroxyl