(Chemical Equation Presented) Mannich-type addition of benzophenone imine glycinates across newly synthesized N-(p-toluenesulfonyl) α- chloroaldimines afforded γ-chloro-α,β-diamino ester derivatives with moderate diastereoselectivity as separable mixtures of anti and syn diastereomers. The γ-chloro-α,β-diamino esters were efficiently cyclized under basic conditions to the corresponding β,γ-aziridino α-amino ester derivatives, representing a new class of conformationally constrained heterocyclic α,β-diamino acid derivatives. The relative configuration of the aziridines was determined via X-ray diffraction analysis. Mechanisms and intermediate transition states to explain the stereochemical outcome of the Mannich reaction with different substrates or under different conditions are proposed. The synthetic importance of the β,γ- aziridino α-amino ester derivatives is demonstrated by their conversion into the corresponding Boc-protected derivatives and ring opening reactions to α,β-diamino esters and a γ-amino α,β-unsaturated amino ester.
ASJC Scopus subject areas
- Organic Chemistry