We previously reported the isolation of Cu-fusaric acid (Cu-FA) complex from the mangrove endophyte Fusarium oxysporum ZZF51. In this study, we explored the mechanism of Cu-FA production in the strain ZZF51 by comparing with that of another endophyte Fusarium sp. B2, which produced FA but not Cu-FA in the same culture condition. The results allowed us to hypothesize that Cu(2+) may act as a "signaling molecule" to awaken the silent FA biosynthetic genes in ZZF51, inducing intracellular production of FA followed by chelation with Cu(2+). This signaling network was triggered specifically by Cu(2+) and may be interfered by other metal ions.

A chiral product, (＋)-2-methoxy-2-methylchroman-7-ol, was obtained from β-cyclodextrin (β-CD)/1,3-dihydroxylbenzene (complex A) and methyl vinyl ketone/β-cyclodextrin (complex B). The reaction was carried out at room temperature in a solid state to give the desired product in 82.8% yield and 78.4% ee. Low optically active product (19.5% ee) was obtained from complex B and 1,3-dihydroxylbenzene (A), and non-optically active product was obtained from complex A and methyl vinyl ketone (B) under the same conditions. The structures of the inclusion compounds were elucidated by melting points, X-ray diffraction, solid-state 13 C CP/MAS NMR (100 MHz, spin＝ 5000), and ROESY analyses. The ratios (1∶1) of host-guest in the inclusion compounds were decided by 1 H NMR spectra (400 MHz). The mechanism of the solid-state conjugated cyclic addition reaction was also discussed.

The title compound, C21H30O, was isolated from the soft coral Sinularia sp. The mol­ecule contains four alicyclic rings, all trans-fused, among which three six-membered rings are in different distorted chair conformations while a five-membered ring assumes an envelope form.