Asymmetric Synthesis of Aromatic and Heteroaromatic α-Amino Acids Using a Recyclable Axially Chiral Ligand

Abstract

In this work, we introduce a new chiral nucleophilic glycine equivalent containing a recyclable axially chiral ligand. As the first synthetic application of this glycine reagent, we describe its alkylation reactions with various alkyl bromides, conducted under unconventional conditions using methanol as the reaction medium. The alkylation products were isolated in diastereomerically pure state in high >80 % yields. The wide structural scope of this method and its limitations are convincingly demonstrated and critically discussed. The recyclable nature of the nonracemizable axially chiral ligands together with the generally excellent stereochemical outcome makes this a very valuable method for the practical preparation of enantiomerically pure aromatic tailor-made α-amino acids.

This work introduces a new chiral nucleophilic glycine equivalent containing a recyclable axially chiral ligand. This glycine reagent undergoes alkylation with various benzylic bromides to give aromatic and heteroaromatic α-amino acids of high pharmaceutical potential. The alkylation products were typically isolated in >80 % yield with excellent diastereoselectivity (up to 99:1).

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