Reanalysis of lindenatriene, a building block for the synthesis of lindenane oligomers

Abstract

Lindenane oligomers isolated from Chloranthus pose significant challenges for chemical synthesis. The structure of a proposed biosynthetic monomer, lindenatriene, was recently called into question. Its attempted synthesis produced a compound whose 1 H NMR spectrum differed significantly from the spectrum of a monomer produced by oligomer pyrolysis. Here we propose that the original structural assignment after pyrolysis was correct and instead the spectra of synthetic materials were misinterpreted. Reanalysis of 2D NMR data suggest that lindenatriene isomerizes (formal [1,7]-hydrogen shift) upon treatment with base.

A comprehensive review on the chemical constituents, sesquiterpenoid biosynthesis and biological activities of Sarcandra glabra

“…Consequently, the discrepancies between the 1 H NMR chemical shifts reported by Yuan et al and those reported by Kawabata et al raised questions regarding the validity of the proposed biogenetic mechanism. Finally, Martinez et al [ 133 ] re-assessed the literature and NMR data, affirming lindenatriene’s continued relevance as a building block in Kawabata’s original biogenetic hypothesis.

Scheme 2 Proposed tautomerisation of lindenatriene and iso -lindenatriene

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