テルペノイド生合成における環縮小および環拡大反応と全合成への応用
Nicolas Kratena1, Nicolas Heinzig1, Peter Gärtner1
1Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9, A-1060, Vienna, Austria.
Abstract:
Terpenoids exhibit remarkable structural diversity, including highly complex ring-expanded or contracted carbocyclic skeletons. This review aims to explore intriguing examples of such ring-size alterations in all aspects of terpenoid synthesis. The current state-of-the-art regarding proposed biosynthetic pathways for terpenoids with unusual carbon skeleta, occurring either during initial cyclisation or subsequent oxidative tailoring, will be examined and discussed. Where possible, biogenetic relationships of closely related families of natural products will be contextualised by showing the mechanistic rationale for their interconversion. In the second part of this article, the application of bioinspired ring contraction and ring-expansion strategies in relevant natural product syntheses will be presented, demonstrating how synthetic chemistry can help to elucidate plausible biogenetic routes for structurally complex natural products.
関連する概念動画
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
Cycloaddition Reactions: Overview
Thermal and Photochemical Electrocyclic Reactions: Overview
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Thermal Electrocyclic Reactions: Stereochemistry
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.


