G. Gondos et al., A new chiral director for the highly diastereoselective borane reduction of steroid-20-ones, MONATS CHEM, 131(10), 2000, pp. 1055-1059
The synthesis of a new chiral boroxazolidine was achieved which was used to
control the stereochemistry of the borane reduction of the 20-keto group o
f steroids. The otherwise hardly accessible 20 alpha-(20S)-alcohol can thus
be prepared in a yield of 91%.