Affiliation:
1. Kekulé Institute of Organic Chemistry and Biochemistry University of Bonn Gerhard-Domagk-Straße 1 53121 Bonn Germany
2. Max Planck Institute for Chemical Ecology Hans-Knöll-Straße 8 07745 Jena Germany
3. Department of Plant Sciences University of Tennessee 2431 Joe Johnson Drive Knoxville TN 37996-4561 USA
Abstract
AbstractThe microbial type sesquiterpene synthase RlMTPSL4 from the liverwort Radula lindenbergiana was investigated for its products, showing the formation of several sesquiterpene hydrocarbons. The main product was structurally characterized as the new compound 4,5‐diepi‐isoishwarane, while the side products included the known hydrocarbons germacrene A, α‐selinene, eremophilene and 4,5‐diepi‐aristolochene. The cyclization mechanism towards 4,5‐diepi‐isoishwarane catalyzed by RlMTPSL4 was investigated through isotopic labeling experiments, revealing the stereochemical course for the deprotonation step to the neutral intermediate germacrene A, a reprotonation for its further cyclization, and a 1,2‐hydride shift along the cascade. The absolute configuration of 4,5‐diepi‐isoishwarane was determined using a stereoselective deuteration approach, revealing an absolute configuration typically observed for a microbial type sesquiterpene.