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A concise synthesis of (16 S ,20 S )-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 3 SiH/TFA or Et 3 SiH/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.

A Convenient Synthesis of (16S,20S)-3β-Hydroxy-5α-pregnane-20,16-carbolactam and Its N-alkyl Derivatives