Four new α-pyrone derivatives phomones C-F (1−4) together with four known compounds (5−8) were isolated from the endophytic fungus Phoma sp. YN02-P-3. Compound 1 is the first example of 6-α,β-unsaturated ester-2-pyrone dimers via intermolecular symmetrical [2 + 2] cycloaddition. The chemical structures of these compounds were determined from spectroscopic data (1D/2D NMR, MS and IR). The acetylated product (9) of 1 along with compounds 1–8 were then tested for their cytotoxicity against HL-60, PC-3 and HCT-116 cell lines. Compounds 2, 3, 5 and 9 with acetyl groups showed significant inhibitory activities against the three cell lines with IC50 values in the range 0.52–9.85 μM. while compounds 1, 4 and 6–8 that possess no acetyl group showed no inhibitory activity (IC50 > 50 μM), indicating that the acetyl group at 10- or 12- are essential for their cytotoxic activities. The structure-activity relationships of these phomones were also reported.Four new α-pyrone derivatives phomones C-F (1–4) together with four known compounds (5–8) were isolated from the endophytic fungus Phoma sp. YN02-P-3. Compound 1 is the first example of 6-α,β-unsaturated ester-2-pyrone dimers via intermolecular symmetrical [2 + 2] cycloaddition. Compounds 2, 3, 5 and the acetylated product (9) of 1 showed significant inhibitory activities against HL-60, PC-3 and HCT-116 cell lines with IC50 values in the range 0.52–9.85 μM.Download high-res image (199KB)Download full-size image