Chemical Modification of Plant Alkaloids. 8. Stereocontrolled T-Reactions of (1R,5S,12S)-Tetrahydrocytisine Derivatives

New heterocyclic quinolizidine systems were prepared from (1R,5S,12S)-tetrahydrocytisine. The synthetic scheme included arylation of tetrahydrocytisine by 2-fluoro-5-nitrobenzaldehyde and condensation of the resulting aldehyde with 1,3-dimethylbarbituric acid. The Knoevenagel intermediate obtained from the condensation was cyclized by a T-reaction to give two spirocyclic products as a derivative with the lupanine skeleton and its regioisomer with the 11,15-diazapentacyclo[11.7.1.02,11.05,10.015,20]heneicosane skeleton. The cyclization occurred highly stereoselectively. The structures of the products were proven using NMR and X-ray crystal structure analyses. © 2018, Springer Science+Business Media, LLC, part of Springer Nature