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

The reaction between the N-Dpp (Dpp = diphenylphosphinoyl) imine 1 a and 5H-oxazol-4-one 2a could be efficiently catalyzed by a zinc catalyst such as the salen 4/Zn complex and an encouraging ee value was obtained along with excellent diastereoselectivity.

Abstract

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. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.