Chemistry - A European Journal
10.1002/chem.201901675
FULL PAPER
Having identified structural similarities with lunularic acid (15), an
allelopathic natural product interacting with the abscisic acid
pathways and inhibiting seed germination and plant growth,23
organic layer was washed 3 times with brine. The aqueous phases were
further extracted 3 times with diethyl ether. The combined organic extracts
were dried over Na SO and concentrated under reduced pressure,
2 4
avoiding heating above 20°C. The residue was then purified by flash
chromatography on silica gel, using a chilled column (<10°C) to furnish
dihydrooxepin 13.
radulanin A (4a) was evaluated on Arabidopsis thaliana seedlings.
It showed remarkable phytotoxic effects at 50 µg/mL after 24h,
with a persistent effect after 120 h (Figure 3), to be compared to
the similar effect of glyphosate at 25 µg/mL. Interestingly, the
dihydrobenzoxepine core alone (24) was nearly inactive at the
concentration of 100 µg/mL. Although the mechanism of action
and toxicity profile of 4a have to be evaluated, such a relatively
simple compound may constitute a new phytopharmaceutical
lead. Indeed, there is an urgent need for alternatives to current
Acknowledgements
We thank Sorbonne Université and the Graduate School of
Molecular Chemistry for providing a PhD grant to WZ. We thank
Mr. Davy Lin for experimental support in the synthesis of
compound 10f. The CNRS, Sorbonne Université and Ecole
Polytechnique are acknowledged for financial supports.
herbicides, some of which, being a subject of controversy, are
threatened to be banned.28
Keywords: 2,5-dihydrooxepines • sigmatropic rearrangement •
density functional calculations • total synthesis • herbicide
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2
before being diluted with Et O and quenched with chilled water (0˚C). The
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