eudesmane

Eudesmane is a parent skeleton used to describe a large family of sesquiterpenes. It is a bicyclic framework consisting of a cyclohexane ring fused to a cyclopentane ring, creating a rigid [6-5] ring system that contains 15 carbon atoms. The eudesmane framework serves as a common scaffold for numerous natural products, especially the eudesmane-type sesquiterpenes and their lactone derivatives.

Biosynthesis and structure: In biosynthetic pathways, farnesyl pyrophosphate is converted through cyclization to a characteristic eudesmane cation, which can undergo various rearrangements and oxidations to yield different substituents and stereoisomers. The resulting diversity arises from the mode of ring fusion, the orientation of substituents, and subsequent functional group elaboration. Because the rings are fused, the framework accommodates multiple stereochemical configurations, contributing to a wide spectrum of natural products.

Occurrence and significance: Eudesmane-type sesquiterpenes are widespread in the plant kingdom and appear in essential oils, resins, and other plant extracts. When oxidized, many eudesmane derivatives form sesquiterpene lactones known as eudesmanolides, a group notable in natural product chemistry for their biological activities. The skeleton also appears in a range of simpler hydrocarbons and reduced forms, illustrating its role as a versatile foundational motif in terpenoid chemistry.

See also: taxonomic and chemotaxonomic relevance of sesquiterpene skeletons; other common sesquiterpene frameworks such as germacrene, guaiane, and cadinene.