Sterculic acid is a cyclopropene fatty acid. It is found in various plants of the genus Sterculia, including being the main component of Sterculia foetida seed oil.[1]
The biosynthesis of sterculic acid begins with the cyclopropanation of the alkene of phospholipid-bound oleic acid, an 18-carbon cis-monounsaturated fatty acid. This transformation involves two mechanistic steps: electrophilic methylation with S-adenosyl methionine to give a carbocationic reactive intermediate, followed by cyclization via loss of H+ mediated by a cyclopropane-fatty-acyl-phospholipid synthase enzyme. The product, dihydrosterculic acid, is converted to sterculic acid by dehydrogenation of the cis-disubstituted cyclopropane to cyclopropene.[2] An additional step of α oxidation removes one carbon from the carboxy chain to form the 17-carbon-chain structure of malvalic acid.