A concise and convergent route to 5,8-disubstituted indolizidine and 1,4-disubstituted quinolizidine ring cores by diastereoselective aza-Diels-Alder reaction.

[reaction: see text] A short and convergent synthesis of 5,8-disubstituted indolizidine and 1,4-quinolizidine scaffolds is described. The key steps of the synthetic pathway are the aza-Diels-Alder reaction of a 2-aminodiene with an N-allyl or N-homoallylaldimine and a ring-closing metathesis. The bicyclic alkaloid analogues are obtained with total diastereoselectivity and through a common pathway.