A Convenient Synthesis of (16S20S)-3β-Hydroxy-5α-pregnane-2016-carbolactam and Its N-alkyl Derivatives

摘要

A concise synthesis of (16 ,20 )-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 Et SiH/TFA or Et SiH/Bi(TfO) . Alternately, the lactone was converted first to the oxo-acid, which was then subjected to the microwave-assisted reductive amination. -Alkyl derivatives were also obtained in a similar way.