Stereoselective intramolecular cycloadditions of homochiral nitrilimines as a source of enantiopure 2,3,3a,4,5,6-hexahydro-pyrrolo[3,4-c]pyrazoles

Abstract: Starting from the methyl esters of glycine, L-alanine, L-phenylalanine and (S)-2-phenylglycine, we developed a synthetic route to the title compounds in the enantiopure form by means of a stereoselective intramolecular 1,3-dipolar cycloaddition of homochiral nitrilimines 5a-d. Fair to good overall product yields and high cycloaddition diastereoselectivity were obtained.