seco‐Labdanes: A Study of Terpenoid Structural Diversity Resulting from Biosynthetic C−C Bond Cleavage

Abstract

The cleavage of a C−C bond is a complexity generating process, which complements oxidation and cyclisation events in the biosynthesis of terpenoids. This process leads to increased structural diversity in a cluster of related secondary metabolites by modification of the parent carbocyclic core. In this review, we highlight the diversifying effect of C−C bond cleavage by examining the literature related to seco‐labdanes—a class of diterpenoids arising from such C−C bond cleavage events.

Remote B-Ring Oxidation of Sclareol with an Engineered P450 Facilitates Divergent Access to Complex Terpenoids

“…Future work in this area will focus on expanding the substrate scope of the transformation through further enzyme engineering. Based on our biomimetic approach toward pallavicinin, it is anticipated that a more general C6 oxidation platform would enable a divergent and efficient access to an even broader range of seco -labdane natural products …”

Investigation of cytochrome P450s in the biosynthesis of rice phytoalexins

“…Based on the activity of MS1 and MS2 indicated in this paper, it is likely these enzymes or similar dehydrogenases convert the CYP71Z6 product to oryzadione. The chemistry of oryzalic acids and oryzalides suggests a C2-C3 bond cleavage which most likely occurs via a Baeyer-Villiger monooxygenase type reaction (Grant & Brimble, 2021). We therefore posit successive CYP-catalyzed Baeyer-Villiger reactions on oryzadione to generate an unstable intermediate (Compound X).…”

“…The oryzalic acids are 2,3-seco-kauranes, with C2 and C3 converted to carboxylic acids. The mechanism of formation of oryzalides and oryzalic acids like other seco labdanes are believed to involve Baeyer-Villiger and Claisen condensation type reactions (Grant & Brimble, 2021). The lack of standards for oryzalides coupled with the paucity of data regarding the oryzalides has made it difficult to study their biosynthesis.…”