A Simple Entry to the 5,8-Disubstituted Indolizidine Skeleton via Hetero Diels-Alder Reaction
Juan Francisco Rodríguez-Caro1, María M Afonso1, José Antonio Palenzuela1
1Departamento de Química Orgánica, Instituto Universitario de Bio-Orgánica Antonio González (SINTESTER), Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez 2, 38206 La Laguna, Spain.
Abstract:
The 5,8-disubstituted indolizidines are the largest family of indolizidines isolated from the skin of amphibians. These compounds exhibit interesting biological activities such as noncompetitive blockers of nicotinic receptors. In this paper, we present a short, simple, and general synthesis of these alkaloids based on the hetero Diels-Alder reaction between suitable monoactivated dienes and Δ1-pyrroline as the dienophile. The selectivity of the process is explained based on computational studies. Concise synthesis of the indolizidine alkaloid 181B from a hetero Diels-Alder reaction was accomplished in four steps.
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