Anti- Agrobacterium tumefactions sesquiterpene derivatives from the marine-derived fungus Trichoderma effusum

can harm various fruit trees, leading to significant economic losses in agricultural production. It is urgent to develop new pesticides to effectively treat this bacterial disease. In this study, four new sesquiterpene derivatives, trichoderenes A-D ( - ), along with six known compounds ( - ), were obtained from the marine-derived fungus . The structures of - were elucidated by extensive spectroscopic analyses, and the calculated ECD, ORD, and NMR methods. Structurally, the hydrogen bond formed between the 1-OH group and the methoxy group enabled to adopt a structure resembling that of resorcylic acid lactones, thereby producing the ECD cotton effect. Compound represents the first example of C12 nor-sesquiterpene skeleton. Compounds - were tested for their antimicrobial activity against . Among them, compounds - and - exhibited inhibitory activity against with MIC values of 3.1, 12.5, 12.5, 6.2, 25.0, and 12.5 μg/mL, respectively.