Catalysis of the reaction: 2-oxo-delta3-4,5,5-trimethylcyclopentenylacetate + ATP + CoA = AMP + diphosphate + 2-oxo-delta3-4,5,5-trimethylcyclopentenylacetyl-CoA.
2-oxo-delta3-4,5,5-trimethylcyclopentenylacetyl-CoA synthetase activity