New organocatalysts derived from tetrahydropapaverine for asymmetric aldol reaction

Synthesis of prolinamide derivatives of (R)-tetrahydropapaverine as mono-, di- and tripeptide is reported. (R)-Tetrahydropapaverine-prolinamide hybrid derivatives were tested as organocatalysts in the asymmetric Aldol reaction of aldehydes and ketones within various solvents, temperatures, and molar ratios. Catalyst 2 (30 mol %) afforded the best result in the Aldol reaction of cyclohexanone with 4-nitrobenzaldehyde up to 90% ee. Although in the sole presence of L-proline the reaction proceeded with anti-stereoselectivity, its hybridization with (R)-tetrahydropapaverine yielded the formation of syn products as the major compounds. [GRAPHICS] .