Having achieved the synthesis and characterization of the enantiomerically pure phosphoric acids (S)-and (R)-PO4H-[9]CPP, we proceeded with their application in asymmetric organocatalysis. We chose the stereoselective hydrogenation of quinolines as a model reaction using the classic Hantzsch ester as a hydride donor (Table ). Our initial optimization was conducted with 2-phenylquinoline (4a) as substrate with (S)-PO4H- [9]CPP at 10 mol% catalyst loading under conditions well-established in the literature. 51 To our delight, we observed an excellent enantioselectivity of 95% ee, with the (S) catalyst favoring the formation of the (R)-hydrogenated quinoline (5a, Table , entry 1). We found that decreasing the catalyst loading from 10 to 5 and 2.5 mol% did not significantly affect the enantioselectivity or the yield of the reaction, provided that the reaction was performed over a sufficient period of time (Table , entry 1-3). For the remaining experiments, we opted for a catalyst loading of 5 mol% as a reasonable compromise between catalyst quantity and reaction times (typically 24 hours). We next compared our catalyst (S)-PO4H- [9]CPP to the simpler BINOL derivatives (S)-PO4H-Ph and (S)-PO4H-Biph, which possess phenyl and biphenyl ortho-substituents, respectively (see Table ). We found that the absence of a confined "pocket" in reference catalysts (S)-PO4H-Ph and (S)-PO4H-Biph (as an extended version, more closely resembling the constitution of the nanohoop), led to a pronounced decrease of the enantioselectivity to 48% and 51% ee, respectively, under otherwise identical reaction conditions (Table , entry 4-5). As a final experiment, we confirmed that the other enantiomer of our catalyst, (R)-