Five Unique Compounds: Xyloketals from Mangrove Fungus Xylaria sp. from the South China Sea Coast

Five unique metabolites, xyloketals A (1), B (2), C (3), D (4), and E (5), and the known 6 were isolated from mangrove fungus Xylaria sp. (no. 2508), obtained from the South China Sea. The structures of these compounds were elucidated by spectroscopic and X-ray diffraction experiments. Xyloketal A is a ketal compound with a C3 symmetry and xyloketals B−E are its analogues. It was found that xytoketal C slowly rearranged to xytoketal B in DMSO-d6 solution at room temperature. Xyloketal A exhibited the activity of inhibiting acetylcholine esterase.