Two New 7‐Dehydrobrefeldin A Acids from Cylindrocarpon obtusisporum, an Endophytic Fungus of Trewia nudiflora

Abstract Two new 7‐dehydrobrefeldin A acids, (2 E ,4 R *)‐4‐hydroxy‐4‐{(1 R *,2 S *)‐4‐oxo‐2‐[(1 E )‐6‐oxohept‐1‐en‐1‐yl]cyclopentyl}but‐2‐enoic acid ( 3 ) and (2 E ,4 R *)‐4‐hydroxy‐4‐{(1 R *,2 S *)‐2‐[(1 E ,6 S *)‐6‐hydroxyhept‐1‐en‐1‐yl]‐4‐oxocyclopentyl}but‐2‐enoic acid ( 4 ), were isolated from the endophytic fungal strain Cylindrocarpon obtusisporum ( Cooke & Harkness ) Wollenw . of Trewia nudiflora , together with two known compounds, 7‐dehydrobrefeldin A ( 2 ) and brefeldin A ( 1 ). Their structures were determined on the basis of extensive 1D‐ and 2D‐NMR‐spectral analysis.