Diterpene

Diterpenes are a class of terpenes comprising four isoprene units, totaling 20 carbon atoms. They are built from the common isoprenoid building blocks isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), which are joined to form geranylgeranyl pyrophosphate (GGPP). Diterpene synthases then convert GGPP into a variety of carbon skeletons, and these skeletons are further modified by oxidations, reductions, and other enzymes to yield a broad array of diterpenoids.

The structural diversity of diterpenes arises from different cyclization patterns and rearrangements of GGPP, producing skeletons such as labdane-type, kaurane-type, clerodane-type, and pimarae-type frameworks. ent-Kaurene is a key intermediate in the biosynthesis of gibberellin plant hormones, while more complex diterpenoids include paclitaxel (Taxol), a potent anticancer agent. Simple examples such as phytol (a diterpene alcohol) and steviol (the non-sugar part of steviol glycosides used as a sweetener) illustrate the range from basic to highly functionalized structures.

Occurrence and applications: Diterpenes are widely produced by plants, fungi, and some marine organisms. They frequently serve ecological roles as defense compounds, signaling molecules, or pigments. In humans, diterpenes are of pharmaceutical and industrial interest, contributing to anticancer drugs, fragrances, flavors, and natural sweeteners. Like other terpenes, their biosynthesis starts from IPP and DMAPP, with diversification driven by specialized diterpene synthases and subsequent enzymatic modifications.