Synthesis of α-sulfanyl-β-amino acid derivatives by using nanocrystalline magnesium oxide

The Mannich-type reaction between alkyl, aryl and heterocyclic aldimines and sulfonium salts for the synthesis of α-sulfanyl-β-amino acid derivatives by using nanocrystalline magnesium oxide (NAP-MgO) is described. These products are obtained in moderate to high yields with moderate diastereoselectivities. The configuration of ethyl-3-{[(4-methylphenyl)sulfonyl]amino}-2-(methylsulfanyl)-3-(4-nitrophenyl)propanoate (major isomer) has been confirmed by X-ray diffraction technique to be anti, and consistent with the assignment based on 1H NMR spectroscopy. These α-sulfanyl-β-amino acid derivatives are important building blocks for pharmaceuticals with potent biological activity.