Preparation of Intermediates for the Synthesis of Polycyclic Alkaloids: A New Access to the Azabicyclic Core of the Stemona Alkaloids

Several isoxazolidines, derived from the 1,3‐dipolar cycloaddition of α,β‐hexenolides to cyclic nitrones, were converted into the corresponding piperidine‐ and pyrrolidine‐oxepinones by reduction of the nitrogen−oxygen bond. The potential of the resulting amino alcohols as synthetic precursors of polycyclic alkaloids was explored. These intermediates provide a new access to the 1‐azabicyclo[5.3.0]decane core of the Stemona alkaloids. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)