Isolated from?Rhodococcus?sp. The bornane ring system is cleaved by a retro-Claisen reaction to give the enol of ¦Á-campholonate. When separate from the enzyme the enol is tautomerised to the keto form as a 6:1 mixture of [(1S,3R)-2,2,3-trimethyl-4-oxocyclopentyl]acetate and [(1S,3S)-2,2,3-trimethyl-4-oxocyclopentyl]acetate.