The tail-to-head terpene tyclization is arguably one. of the most complex reactions found in nature. The hydrogen-bond-based resorcinarene capsule represents the first "man-made enzyme-like catalyst that is capable of catalyzing this reaction. Based on noncovalent-interactions' between the 'capsule and the substrate, the product selectivity can be tuned by using different leaving groups. A detailed mechanistic investigation was performed to elucidate the reaction, mechanisril. For the cyclization of geranyi acetate, it was found that the cleavage. of the leaving group is the rate-determining step. Furthermore, the studies revealed that trace amounts of add are required as cocatalyst. A series of control experiments demonstrate that a synergistic interplay between the supramolecular capsule and the acid traces is, required for catalytic activity.