¹³C NMR determination of the configuration of methyl‐substituted double bonds in medium‐ and large‐ring terpenoids

Abstract

Abstract 13 C NMR spectroscopy can be used to determine the configuration of methyl‐substituted double bonds in medium‐ and large‐ring terpenoid natural products. A number of examples from our investigations in the germacranolide field are presented, and clearly show that if the resonance for the vinylic methyl group appears at a value greater than 20 ppm the double bond has a ( Z )‐configuration whereas if the value is less than 20 ppm an ( E )‐configuration is present. Literature examples of other classes of compounds are also cited to illustrate the generality of this method.