Highly Diastereo‐ and Enantioselective Synthesis of α‐Alkyl Norstatine Derivatives: Catalytic Asymmetric Mannich Reactions of 5H‐Oxazol‐4‐ones

Going Mannich: The title reaction results in the first catalytic asymmetric synthesis of syn-α-alkyl norstatine derivatives. Excellent enantioselectivities and diastereoselectivities were achieved with a series of N-diphenylphosphinoyl-protected imines and 5H-oxazol-4-ones by using the catalyst 1/Zn. Importantly, the involvement of the diethyl phosphoramidate 2 was critical to achieve good enantioselectivities in the present Mannich reaction.