A Novel Synthetic Approach from Diosgenin to a 17α‐Hydroxy Orthoester via a Regio‐ and Stereo‐Specific Rearrangement of an Epoxy Ester

Abstract

A cholesterol model compound, containing 16β‐acetoxy, 17α‐hydroxy, and (20S, 22R)‐epoxy groups was synthesized from diosgenin in 13 steps and was rearranged regio‐ and stereo‐specifically to an orthoester with BF₃·Et₂O.

Keywords:

• Orthoester
• Epoxy ester
• Regio-specific and stereo-specific rearrangement
• Diosgenin
• Cholesterol

Acknowledgments

N.C. is a Ph.D student under the Royal Golden Jubilee Program, the Thailand Research Fund (TRF). We are grateful for the financial support from the TRF, through the Royal Golden Jubilee Program. Part of the research was conducted by N.C. as a guest worker in the Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH). We thank Dr. John W. Daly and Dr. Thomas F. Spande for helpful suggestions and discussions. Some ¹H, ¹³C NMR and mass spectral data were kindly provided by Prof. Walter C. Taylor, University of Sydney, Australia, Mr. Wesley White, Dr. H. J. C. Yeh and Mr. Noel Whittaker, NIDDK, NIH. We also are indebted to Assistant Professor Palangpon Kongsaeree, x‐ray Crystallographic Laboratory, Mahidol University for x‐ray crystallography of compound 13b.