In a screening of micro-organisms for new secondary metabolites, two unprecedented tricyclic highly functionalized ketal-lactone metabolites, named lucknolide A (1) and lucknolide B (2), have been isolated, and the compounds were characterized by extensive NMR and mass spectroscopic studies. Single-crystal X-ray diffraction experiments on 1 and 2 were performed, and the absolute configuration of 1 was determined.