Access to 27-Nortomatidine and 27-Norsoladulcidine Derivatives

Synthesis
of (22R)- and (22S)-27-norspirosolane
alkaloids from tigogenin, epismilagenin, and smilagenin is described.
The alkaloids were prepared from readily available dinorcholanic lactones
via their reaction with 4-chlorobutyllithium followed by substitution
of chloride with azide and reductive N-cyclization
under the Staudinger conditions.