Highly diastereoselective addition of nitromethane anion to chiral α-amidoalkylphenyl sulfones. Synthesis of optically active α-amino acid derivatives

Abstract

Optically active syn-α-amidoalkylphenyl sulfones can be prepared from chiral aldehydes in anhydrous conditions using benzenesulfinic acid. These sulfones in basic conditions give N-acylimines that react with sodium methanenitronate to afford the corresponding nitro adducts with high anti diastereoselectivity. PM3 semiempirical calculations provide a rationale for the observed opposite stereoselectivity. The obtained nitro derivatives undergo a Nef reaction followed by a methylation giving optically active β-hydroxy-α-amino acid and α,β-diamino acid esters in good yield. These amino acid derivatives are important building blocks for the preparation of biologically active compounds.