Studies on the Metabolism of Unsaturated Fatty Acids. I. Synthesis and Identification of 6-Hydroxydodec-3-cis-enoic Acid, the Final Metabolite of Ricinoleic Acid by Escherichia coli K-12

6-Hydroxydodec-cis-3-enoic acid was synthesized to identify a metabolite of ricinoleic acid by Escherichia coli and to use it as substrate in the investigation on unsaturated fatty acid metabolism. In a total synthesis of the 6-hydroxy acid, the key step involved the reaction of the trialkynylborane with ethyl diazoacetate. Dec-1-yn-4-ol was lithiated after protection of the hydroxyl group with dihydropyran, and was transformed into the trialkynylborane by treating with boron trifluoride etherate. The subsequent reaction with ethyl diazoacetate afforded the 6-hydroxy-3-ynoate, which was hydrogenated over Lindlar catalyst to yield 6-hydroxydodec-3-cis-enoic acid. The results obtained by gas chromatography-mass spectrometry (GC-MS) showed that the final metabolite of ricinoleic acid by E. coli was identical with the synthetic 6-hydroxy acid.