Sterculic acid is a

cyclopropene fatty acid Cyclopropane fatty acids (CPA) are a subgroup of fatty acids that contain a cyclopropane group. Although they are usually rare, the seed oil from lychee contains nearly 40% CPAs in the form of triglycerides. Biosynthesis CPAs are derived from un ...

. It is found in various plants of the genus '' Sterculia'', including being the main component of '' Sterculia foetida'' seed oil.

Biosynthesis

The

biosynthesis Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. ...

of sterculic acid begins with the cyclopropanation of the

alkene In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

phospholipid Phospholipids, are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...

-bound

oleic acid Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a monounsaturated omega ...

, an 18-carbon ''

cis Cis or cis- may refer to: Places * Cis, Trentino, in Italy * In Poland: ** Cis, Świętokrzyskie Voivodeship, south-central ** Cis, Warmian-Masurian Voivodeship, north Math, science and biology * cis (mathematics) (cis(''θ'')), a trigonome ...

''-

monounsaturated fatty acid Monounsaturated fats are fatty acids that have one double bond in the fatty acid chain with all of the remainder carbon atoms being single-bonded. By contrast, polyunsaturated fats have more than one double bond. Molecular description Fatty aci ...

. This transformation involves two mechanistic steps:

electrophilic In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carri ...

methylation with ''S''-adenosyl methionine to give a

carbocation A carbocation is an ion with a positively charged carbon atom. Among the simplest examples are the methenium , methanium and vinyl cations. Occasionally, carbocations that bear more than one positively charged carbon atom are also encountere ...

reactive intermediate In chemistry, a reactive intermediate or an intermediate is a short-lived, high-energy, highly reactive molecule. When generated in a chemical reaction, it will quickly convert into a more stable molecule. Only in exceptional cases can these comp ...

, followed by cyclization via loss of H⁺ mediated by a

cyclopropane-fatty-acyl-phospholipid synthase In enzymology, a cyclopropane-fatty-acyl-phospholipid synthase () is an enzyme that catalyzes the chemical reaction :S-adenosyl-L-methionine + phospholipid olefinic fatty acid \rightleftharpoons S-adenosyl-L-homocysteine + phospholipid cyclopropan ...

enzyme. The product, dihydrosterculic acid, is converted to sterculic acid by

dehydrogenation In chemistry, dehydrogenation is a chemical reaction that involves the removal of hydrogen, usually from an organic molecule. It is the reverse of hydrogenation. Dehydrogenation is important, both as a useful reaction and a serious problem. At ...

of the ''cis''-disubstituted

cyclopropane Cyclopropane is the cycloalkane with the molecular formula (CH2)3, consisting of three methylene groups (CH2) linked to each other to form a ring. The small size of the ring creates substantial ring strain in the structure. Cyclopropane itself ...

cyclopropene Cyclopropene is an organic compound with the formula . It is the simplest cycloalkene. Because the ring is highly strained, cyclopropene is difficult to prepare and highly reactive. This colorless gas has been the subject for many fundamental st ...

. An additional step of α oxidation removes one carbon from the carboxy chain to form the 17-carbon-chain structure of malvalic acid.

References

Fatty acids Cyclopropenes {{organic-compound-stub