Xyloketal F: A Strong L ‐Calcium Channel Blocker from the Mangrove Fungus Xylaria sp. (#2508) from the South China Sea Coast

Xyloketal F (1), an unusual metabolite with strong L‐calcium channel blocking activity, was isolated from the mangrove endophytic fungus Xylaria sp. (#2508) collected at the South China Sea coast. Its structure was elucidated by spectral and single‐crystal X‐ray diffraction analysis. The absolute configuration of 1 was determined by the method of quantum‐mechanical calculation of CD spectra. Compound 1 was also synthesized by condensation of xyloketal B with formaldehyde. The L‐calcium channel blocking activities of xyloketals B, A, and F were determined, and at the same concentration (0.03 μmol/L), the inhibiting rates were 12.05 %, 21.47 %, and 50.33 % respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)