A synthetic method was developed for converting the readily available dehydroepiandosterone (la) to 3β-acetoxy-5β,14α-bufa-20,22-dienolide (11). Important steps in the transformation included condensation of ketone lb with diethyl cyanomethylphosphonate to afford olefin 2. Selective reduction of olefin 2 provided formate 4 which was successively oxidized (5) and reduced to ketone 6b. Application of the Henbest reagent (trimethyl phosphite-chloroiridic acid) to reduction of ketone 6b provided a convenient pathway to 3β alcohol 7b. The remaining steps to bufadienolide 11 proceeded via intermediates 8, 9, and 10.
ASJC Scopus subject areas
- Organic Chemistry