Enantioselective Ribozyme Catalysis of a Bimolecular Cycloaddition Reaction This work was supported by the Deutsche Forschungsgemeinschaft (Grant no.: Ja 794/3-1) and the Bundesministerium für Bildung und Forschung (Grant no.: BEO 0311861). We thank Dr. S. Klußmann and Dr. S. Vonhoff (Noxxon Pharma AG, Berlin) for the synthesis of the L-ribozyme.