Structure and biologicalactivity of demethyleneldelidine and its dihydro-γ-lactone

An excess of periodic acid was reacted with the diterpenoid alkaloid demethyleneldelidine (1) to produce a γ-lactone (2) in which the carbonyl at the C6-position was selectively reduced by an excess of NaBH4. The conformation of the rings, configuration of asymmetric and spiro centers, and the nature of intramolecular H-bonds in the diterpenoid alkaloid demethyleneldelidine and its reduction product 3 were analyzed by an x-ray structure analysis. The spiro center at C10 in 3 had the S-configuration. The other asymmetric centers retained the absolute configuration characteristic of alkaloids with the lycoctonine carbon skeleton. The pharmacological properties did not change significantly despite the large difference in the carbon skeletons of γ-lactone 3 and starting 1.