Phomopsisin A-C (1 3), three new leucine-derived cytochalasan alkaloids bearing methylation deficient skeleton were isolated from Phomopsis sp. sh917, an endophytic fungus colonized in the stems of Isodon eriocalyx var. laxiflora. Their structures and absolute configurations were determined through synergetic use of extensive spectroscopic analysis, quantum chemical calculations, and X-ray crystallographic analysis. Noteworthily, 1 represents the first example of cytochalasan possessing an unusual 2H-isoxazole moiety. Additionally, their cytotoxic and anti-inflammatory activities were initially evaluated, and 3 showed a moderate inhibitory effect against the NO production. (C) 2020 Elsevier Ltd. All rights reserved.