Synthesis of Dipeptides via Addition of N‐(Nitroacetyl)amino‐Acid Derivatives to Michael Acceptors: Scope, Stereoselectivity, and Absolute Configuration

Abstract

Michael addition of N‐nitroacetyl derivatives 1 of proline esters using KF under phase‐transfer catalysis resulted in the formation of adducts 3–9 with chemical yields ranging from 40–90% (Scheme). Stereoselectivity of up to 51% was obtained on addition of benzyl N‐(nitroacetyl)‐L‐prolinate (1a). The absolute configuration at the newly created chiral centre was established in the case of 9 by carrying out a reductive acylation and comparing the product 10 with an authentic sample of ethyl N‐(O⁵‐ethyl N²‐acetyl‐L‐glutam‐1‐yl)‐L‐prolinate (L, L‐10).