dimethylallyl

Dimethylallyl refers to the five-carbon branched allyl substituent derived from 3,3-dimethyl-1-propene. In biochemical contexts it is most commonly encountered as part of the dimethylallyl pyrophosphate (DMAPP) group, which together with isopentenyl pyrophosphate (IPP) provides the two C5 building blocks of isoprenoids. The dimethylallyl moiety is the branched end of the DMAPP molecule and serves as the donor component in prenyltransferase-catalyzed condensations that extend the prenyl backbone. For example, condensation of DMAPP with IPP yields geranyl pyrophosphate (GPP, C10); further addition of IPP units produces farnesyl pyrophosphate (FPP, C15) and longer isoprenoid chains. These reactions underpin the biosynthesis of a wide range of natural products, including terpenes, carotenoids, sterols, and ubiquinones.

In synthetic chemistry, the dimethylallyl fragment is used as a handle for prenylation reactions, where a dimethylallyl or related prenyl group is transferred to substrates such as aromatic rings or proteins, often to modulate activity or solubility. The term dimethylallyl is sometimes used interchangeably with the isoprenyl group in older literature, though the two are distinct positional isomers in the broader isoprenoid family.

The name derives from the 3,3-dimethyl-1-propenyl framework, a hallmark of the DMAPP-derived prenyl donor in many biosynthetic pathways.