Some observations on solasodine reactivity

- The oxidation of N,O-diacetylsolasodine with nitrite reagents results in partial degradation of the side chain.
- The reaction of N,O-diacetylsolasodine with TMSOTf leads to the corresponding pseudosapogenin.
- The crude pseudosapogenin readily undergoes autoxidation to pregna-5,16-dien-3β-ol-20-one acetate.

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.

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