Asymmetric Organocatalytic Synthesis of trans-3,4-Disubstituted Isochromanones via an Intramolecular Aldol Reaction

Abstract

The diastereo- and enantioselective synthesis of 3-acetyl-4-hydroxyisochroman-1-ones via an intramolecular <i>trans</i>-selective aldol reaction employing proline-type organocatalysts is described. Good yields (64–88%) and high stereoselectivities (87 to >95% de, 84–99% ee) are obtained, thus potentially enabling, for example, a new direct entry to carbazolelactone alkaloid natural products.