Some observations on solasodine reactivity
This article presents new transformations of solasodine – a representative steroid alkaloid sapogenin from the Solanum family. Oxidation of N,O-diacetylated solasodine with either NaNO2/BF3·Et2O or t-BuONO/BF3·Et2O resulted in partial degradation of the side chain to (20S)-3β-acetoxypregn-5-ene-20,16β-carbolactone (vespertilin acetate). The same starting compound when treated with TMSOTf afforded the corresponding pseudosapogenin after aqueous work-up. However, when the crude reaction mixture was directly subjected to purification on a silica gel column, efficient autoxidation to pregna-5,16-dien-3β-ol-20-one acetate was observed. One-step synthesis of this important drug intermediate from spirosolan alkaloids may be potentially exploited for large-scale production of steroid hormones.