In addition, we tested two
metabolites showing two different substituent groups at C-6
of (1). When a benzyloxy group was located at the C-6 position
as in (2), the inhibitory effect of (1) in O. crenata germination
was lost; however, when at the same position of the benzene
ring was substituted by a chloroacetyl group as in (3), the
inhibitory effect of (1) was greatly enhanced. The comparison
between the resonance structures of these two 6-substituted
derivatives of (1) (Supporting Information Figure S1) showed
a negative charge on the aromatic ring and a positive charge on
the oxazolinone nitrogen.