Reduction of 1,4-dien-3-one steroids with LiAl2H4 or NaB2H4: stereospecific deuterium-labeling at the c-1alpha position of a 4-en-3-one steroid.

Reduction of a double bond at C-1 of 1,4-dien-3-one steroids 7 and 8 with LiAl2H4 in THF or NaB2H4 in MeOH and H2O gave stereospecifically [1alpha-2H]-labeled 4-en-3-one steroids 9 and 10, respectively. When the deuterated solvents, MeO2H and 2H2O, were used for the reaction of steroid 8 with NaB2H4, [1alpha,2xi-2H2]-labeled compound 10 was produced. This indicates that the reaction proceeds through the initial hydride attack at the C-1alpha position, followed by ketonization of the 2-en-3-ol intermediate.