Synthesis of Diels-Alder adducts of the quinolizidine alkaloids N-methylcytisine, (-)-leontidine, and (-)-thermopsine with N-phenylmaleimide

The Diels-Alder adducts of the quinolizidine alkaloids N-methylcytisine, (-)-leontidine, and (-)-thermopsine with N-phenylmaleimide have been synthesized. The structures and absolute configurations of the new asymmetric centers of the products were determined by NMR spectroscopy experiments, QC-calculations, and X-ray data. (C) 2013 Elsevier Ltd. All rights reserved.