Synthesis of stable isotope labeled analogs of phytanic acid for separate and combined tracing of alpha-, beta- and omega-oxidation.

Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) is a branched very long chain fatty acid (VLCFA) derived in humans from the diet and catabolized via peroxisomal metabolism. Catabolism of phytanic acid is important in humans as certain inborn errors of peroxisomal metabolism, including Refsum Disease, manifest when catabolism of diet derived phytanic acid is impaired. We developed a novel, linear, unified, unoptimized synthesis of all-racemic phytanic acid along with its 2,3,6,7,10,11,14,15-d8, 1,2-13C2, and 1,2-13C2-2,3,6,7,10,11,14,15-d8 stable isotope labeled analogs from commercially available materials including the common starting material ethyl 2-bromoacetate and ethyl 2-bromoacetate-13C2. This improves upon previous synthetic work to provide a simple synthetic route to produce amounts of stable isotope labeled analogs useful for biochemical studies. The neutron encoded position of the stable isotope enrichment allow distinct examination of oxidative pathways of catabolism, allowing comparison of alpha, beta, and omega oxidation through the combination of labels. This provides a useful set of stable isotope labeled analogs for studies of phytanic acid and branched VLCFA metabolism.