Xyloketal H from the mangrove endophytic fungus Xylaria sp 2508

(3R*, 3aR*, 9aR*)-3,9a-Dimethyl- 2,3,3a,9a-tetrahydro-4H-furo[2,3-b]chromene-5,7-diol (xyloketal H), a representative of a new family of xyloketals, was isolated from the marine-derived mangrove fungus Xylaria sp. 2508. Its structure was elucidated by spectroscopic data and single-crystal X-ray diffraction analysis.