Tetrahydropyran-based dipeptides as asymmetric catalysts for a 1,4-addition reaction

Trabajo presentado en la XXVI Reunión Bienal de Química Orgánica de la Real Sociedad Española de Química, celebrada en Punta Umbría, Huelva (España) del 14 al 17 de junio de 2016.A new series of hybrid dipeptide-like organocatalysts based on pyranoid ¿- or ¿-amino acids and proline have been prepared for the asymmetric Michael addition of aldehydes to ß-nitrostyrenes. The reaction proceeds under mild conditions to afford a wide range of ¿-nitroaldehydes with up to 98% yield and up to 96% ee. These dipeptides are bifunctional organocatalysts, with a proline at the N-terminus and a carboxylic acid at the C-terminus. The tetrahydropyran unit embedded in the ¿- or ¿-amino acid induces a well-defined conformation that is responsible for the catalysis. These dipeptides represent a new type of organocatalyst with a large number of possibilities to modulate their reactivity and selectivity.Peer Reviewe