 Squalene

Squalene is a thirty-carbon unsaturated hydrocarbon, ${\mathrm{C}}_{30}{\mathrm{H}}_{50}$, with six carbon–carbon double bonds.^[ref] Its long chain can be folded and cyclized during the biosynthesis of sterols, making it a useful connection between an acyclic precursor and complex fused-ring structures.

The sequence and geometry of the double bonds matter: they determine which groups can approach during a cyclization. Biological pathways use enzymes to control that geometry and the reaction cascade. Hydrogenation of the double bonds changes the compound's identity, rather than merely purifying the original squalene.

Squalene is a naturally occurring organic compound that is classified as a triterpene. It is found in various sources, including plants, animals, and organisms. In nature, squalene serves as a precursor in the biosynthesis of sterols, such as cholesterol, and is vital for cellular function.