Abstract
Novel asymmetric intramolecular Michael addition by chirall amide anions to α,β-unsaturated esters were performed for the asymmetric syntheses of (S)-2-oxo-5-pyrrolidine acetic acid 7 and 2-oxo-6-piperidine acetic acid 14. These acids were respectively related to (S)-(-)ecgoninic acid and (S)-(-)-sedamine in order to determine their absolute configurations. The unnatural amino acids [24, 25, 26] obtained by NaBH_4 reduction of the corresponding lactams were utilized for the asymmetric synthesis of the key steroid C/D intermediate 22. The mechanism of this asymmetric aldol condensation is also discussed.
