geranyl

Geranyl is a hydrocarbon substituent derived from the monoterpene alcohol geraniol by removal of the hydroxyl hydrogen, resulting in a 10-carbon chain with two double bonds. In nomenclature, it is typically described as (E)-3,7-dimethyl-2,6-octadien-1-yl, reflecting its structure and the stereochemistry inherited from geraniol. The corresponding radical form, the geranyl radical, is the neutral C10H17 moiety used in synthesis and enzymatic processes.

Chemically, the geranyl group is a linear isoprenoid unit bearing two conjugated double bonds and two methyl substituents at C3 and C7. The configuration of the double bonds in the common form is usually E (trans). The attachment point is at the terminal carbon (the 1-yl position), which allows it to serve as a substituent on larger molecules or as a donor fragment in enzymatic transfers.

Biologically and chemically, the geranyl group is a key C10 unit in terpenoid biosynthesis. It forms part of geranyl diphosphate (GPP), the central donor in the formation of monoterpenes. GPP is produced from isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) and can be transferred to various acceptors by prenyltransferases, enabling the biosynthesis of many monoterpenoids.

Applications of the geranyl group include its use as a building block in organic synthesis and in fragrance and flavor chemistry, where geranyl derivatives contribute to the scent and aroma of numerous essential oils and natural products.