The new lignan derivative, erimopyrone, was isolated from the liverwort, Mo
erckia erimona. Its structure was established as [1R, 2S]-1(6-carboxy-2-oxo
-2H-4-pyranyl)-6,7-dihydroxy-1,2-dihydro-2,3-naphthalenedicarboxylic acid b
y spectroscopic methods.