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13 C NMR determination of the configuration of methyl‐substituted double bonds in medium‐ and large‐ring terpenoids
Author(s) -
Lange Gordon L.,
Lee Moses
Publication year - 1986
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260240804
Subject(s) - chemistry , double bond , ring (chemistry) , terpenoid , stereochemistry , absolute configuration , resonance (particle physics) , methyl group , nuclear magnetic resonance spectroscopy , group (periodic table) , organic chemistry , atomic physics , physics
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.