Preparation ofsyn-δ-Hydroxy-β-amino Esters via an Intramolecular Hydrogen Bond Directed Diastereoselective Hydrogenation. Total Synthesis of (3S,4aS,6R,8S)-Hyperaspine

Hydrogenation of delta-hydroxy-beta-ketoester-derived enamines 8 produces syn-delta-hydroxy-beta-amino esters 9 diastereoselectively, which may be directed by the formation of an intramolecular hydrogen bond between the delta-hydroxyl and beta-amino groups. By using this method and a Dieckmann reaction as the key steps, (3S,4aS,6R,8S)-hyperaspine, a new type of ladybird alkaloid, is synthesized. [reaction: see text]