Based on at erpenoid overproduction platform in yeast for genome mining,achimeric diterpene synthase from the endophytic fungus Colletotrichum gloeosporioides ES026 was characterized as the (5R,12R,14S)-dolasta-1(15),8-diene synthase.T he absolute configuration was independently verified through the use of enantioselectively deuterated terpene precursors,w hichu nequivocally established the predicted C1-III-IV cyclization mode for this first characterized clade II-D enzyme.Extensive isotopic labeling experiments and isolation of the intermediate (1R)-d-araneosene supported the proposed cyclization mechanism.