Related Experiment Video
Updated: Jun 19, 2026

Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine
Published on: June 13, 2022
Total syntheses of (+)-echinopine A and B: determination of absolute stereochemistry
Thomas Magauer1, Johann Mulzer, Konrad Tiefenbacher
1University of Vienna, Institute of Organic Chemistry, Wahringerstrasse 38, 1090 Vienna, Austria. thomas.magauer@univie.ac.at
Abstract:
The first total syntheses of the novel 3,5,5,7-sesquiterpenoids (+)-Echinopine A (1) and B (2) were achieved. Thereby the proposed structures were confirmed, and the absolute stereochemistry was determined. The key features are (1) the stereoselective installation of the vinyl-moiety on the concave side of the bicyclo[3.3.0]octane core via Myers' [3,3]-sigmatropic rearrangement, (2) the finding that the substituent on the C7 position next to the ketone can be epimerized to the desired concave face under basic conditions, (3) the closure of the highly strained seven-membered ring via RCM, and (4) the unusual C2-homologation of a vinyltriflate with a ketene silyl acetal.
Related Concept Videos
Prochirality
E1 Reaction: Stereochemistry and Regiochemistry
E2 Reaction: Stereochemistry and Regiochemistry
When a substrate with two different β hydrogens undergoes an E2 elimination, the presence of a strong base can yield two regioisomeric alkenes. The more-substituted alkene is the major product and...
Properties of Enantiomers and Optical Activity
¹H NMR Chemical Shift Equivalence: Enantiotopic and Diastereotopic Protons
In chiral compounds such as 2-butanol, replacing the methylene hydrogens at C3 produces a pair of...
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.

