Asymmetric synthesis of 2-alkyl-substituted tetrahydroquinolines by an enantioselective aza-Michael reactionElectronic supplementary information (ESI) available: Copies of 1H and 13C NMR spectra and chiral HPLC chromatograms for 6b. See DOI: 10.1039/c2ob25122a

An optically active tetrahydroquinoline intermediate ( 5 ) was prepared in 8 steps from monoprotected ethylene glycol, using a Pd-catalysed aza-Michael reaction to induce chirality. This can be transformed into three Galipea alkaloids (angustureine, galipeine and cuspareine). The proximity of a benzyloxy group is found to exert profound effects in several steps of the synthesis. Three Galipea alkaloids (angustureine, galipeine and cuspareine) were derived from an enantiomerically pure tetrahydroquinoline intermediate, prepared by a Pd-catalysed aza-Michael reaction.