Access to Guaianolides: Highly Efficient Stereocontrolled Total Synthesis of (±)‐Geigerin

Abstract

Geiger‐Zähler: Die erste Totalsynthese des Guaian‐8,12‐olids Geigerin (3) gelang in acht regio‐ und stereokontrollierten Stufen ausgehend vom Tropyliumkation. Auf dem Weg dorthin wurde das Guaian‐6,12‐olid 2 in zwei Stufen aus dem Hydroazulenon 1 erhalten.

Diversity‐Oriented Synthesis of Diverse Polycyclic Scaffolds Inspired by the Logic of Sesquiterpene Lactones Biosynthesis

“…The use of t BuOOH in the presence of copper catalysts33 yielded an unidentifiable product. From intermediate 20 , access to geigerin ( 3 ) and deoxygeigerin ( 4 ) could be envisioned following the same approach used by Carret and Deprés,34 namely a lithium perchlorate catalyzed 1,6‐conjugate addition of a silyl enol ether. It was found important to deprotect the allylic alcohol 20 for the conjugate addition to proceed.…”

Applications of ultrasound in total synthesis of bioactive natural products: A promising green tool

“…are 100% atom efficient and cycloaddition reactions have a profound role in the synthesis of bioactive natural products as a green methodology [52] , [53] , [54] . An efficient stereocontrolled first total synthesis of a guaianolide (±)-geigerin ( 28 ) was completed by Depres et al from commercially available tropylium cation ( 24 ) through cycloaddition reaction under ultrasonic irradiation [55] . Guaianolides, which contains a bicyclo[5.3.0]decane skeleton, a large group of naturally occurring sesquiterpene lactones [56] .…”

Diversity‐Oriented Synthesis of Diverse Polycyclic Scaffolds Inspired by the Logic of Sesquiterpene Lactones Biosynthesis

“…The use of tBuOOH in the presence of copper catalysts [33] yielded an unidentifiable product. From intermediate 20, access to geigerin (3) and deoxygeigerin (4) could be envisioned following the same approach used by Carret and DeprØs, [34] namely a lithium perchlorate catalyzed 1,6-conjugate addition of a silyl enol ether. It was found important to deprotect the allylic alcohol 20 for the conjugate addition to proceed.…”