Abstract
A concise synthesis of (16S,20S)-3β-hydroxy-5α-pregnane-20,16-carbolactam from tigogenin via the corresponding lactone is described. The most efficient synthetic route consisted of the lactone ring-opening with aminoalane reagent followed by PDC or Dess-Martin oxidation. The oxo-amide obtained was subjected to cyclization with Et3SiH/TFA or Et3SiH/Bi(TfO)3. Alternately, the lactone was converted first to the oxo-acid, which was then subjected to the microwave-assisted reductive amination. N-Alkyl derivatives were also obtained in a similar way.
Highlights
IntroductionMuch attention has been paid to the preparation and biological activity evaluation of 23,24-bisnorcholano-22,16-lactones (bisnorcholanic lactones) [1]
In recent years, much attention has been paid to the preparation and biological activity evaluation of 23,24-bisnorcholano-22,16-lactones [1]
The key step of the lactam synthesis was the cyclization of the obtained oxo-amide 3b to the desired γ-lactam
Summary
Much attention has been paid to the preparation and biological activity evaluation of 23,24-bisnorcholano-22,16-lactones (bisnorcholanic lactones) [1]. One of them, (16S,20S)-3βhydroxy-pregn-5-ene-20,16-carbolactone (vespertilin; Figure 1), is a natural product isolated from. Other bisnorcholanic lactones have been isolated from different plants [3,4,5]. The lactones usually occur in plants as glycosides with sugar linked to the oxygen atom of aglycone at C3. Vespertilin shows a variety of biological activities including anticancer, antifungal, and bactericidal [6].
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