[structure: see text] The total synthesis of the putative structure of the Stemona alkaloid stemonidine has been completed. The key transformations include a 1,3-dipolar cycloaddition of a chiral nitrone derived from (S)-prolinol and a spirolactonization process involving the generation of the critical stereocenter. The NMR data of the synthetic material do not match those reported for the natural product. It is concluded that the structure assigned to stemonidine is incorrect, and it must be reassigned as stemospironine.

A general strategy for the construction of the 1-azabicyclo[5.3.0]decane core of Stemona alkaloids is developed. Our diversity-oriented approach exploits 1,3-dipolar cycloaddition of five-membered cyclic nitrones to C(6) olefins, followed by N-O reductive cleavage and azepine closure. The use of various enantiopure pyrroline N-oxides allows for a practical, stereoselective preparation of several putative precursors of different Stemona alkaloids.

The ethyl carbamate of norpandamarilactonine‐A was prepared in an enantiomerically pure form starting from (S)‐prolinol. Deprotection of the amine functionality rendered both diastereomeric norpandamarilactonines as racemates, which were used as synthetic precursors of pandamarilactonine‐A and ‐B. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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Alkaloids U 0600Total Synthesis of the Putative Structure of Stemonidine: The Definitive Proof of Misassignment. -The title alkaloid is shown to have structure (I) and not (II) which has to be reassigned as stemospironine. -(SANCHEZ-IZQUIERDO, F.; BLANCO, P.; BUSQUE, F.; ALIBES, R.; DE MARCH, P.; FIGUEREDO*, M.; FONT, J.; PARELLA, T.; Org. Lett. 9 (2007) 9, 1769-1772; Dep. Quim., Univ. Auton.