Hydrotitanation-Protonation of Vitamin D2 and Its Analogues: An Efficient Method for the Preparation of 10,19-Dihydrovitamins D2 Including Dihydrotachysterol2

Article abstract of DOI:10.1021/jo00261a020

In this study we describe an easy and efficient method for the preparation of the known 10,19-dihydrovitamins D₂ 2b (DHV₂-II), 2c (DHV₂-IV), 3c (dihydrotachysterol₂, DHT₂), and the new dihydrovitamins D2 2f and 2g.This method is based on the regioselective hydrometalation reaction of vitamin D₂ and its derivatives with the system Cp2TiCl2-LiAlH4 or Cp2TiCl2-Red-Al (Aldrich).Under optimal conditions, the reaction with the former of these hydrometalating systems takes place with a high degree of stereoselectivity and allows labelling at C-19.