Chiral amphiphilic conjugate catalysts were designed and synthesized by covalently connecting l-proline with an inexpensive natural product, isosteviol. These catalysts demonstrated remarkable efficiency in the asymmetric alpha-aminoxylation of aldehydes and ketones using nitrosobenzene in phosphate buffer solution, resulting in good to high yields and excellent enantioselectivities without using any additives. At pH 9.1, the amphiphilic catalysts showed a pH responsive ability in phosphate buffer solution, which facilitated the excellent O-selectivity reactions, illustrating a viable approach for the development of asymmetric supra-molecular catalysts.