Three chlorinated metabolites having a structural similarity to terrein have been isolated from fermentations of Sporormia affinis Sacc., Bomm and Rouss. Single crystal X-ray analysis was used to show the structure and absolute configuration of the major dichlorinated metabolite to be (lS,5S)-2-cyclopentene-1-carboxylic acid, 2-trans-allyl-3,5-dichloro-l-hydroxy-4-oxo methyl ester (1). Spectral data and ORD studies were then used to assign the structures (lS,5S)-2-cyclopentene-1-carboxylic acid, 2-trans-allyl-3-chloro-1-hydroxy-4-oxo methyl ester (II) and (lS,5R)-2-cyclopentene-1-carboxylic acid, 2-trans-allyl-3-chloro-l-hydroxy-4-oxo methyl ester (III), respectively to the monochlorinated compounds. © 1969, American Chemical Society. All rights reserved.