Stereochemistry of NaBH4 Reduction of a 19-Carbonyl Group of 3-Deoxy Androgens. Synthesis of [19S-3H]- and [19R-3H]-Labeled Aromatase Inhibitors Having a 19-Hydroxy Group
aromatase, the [19S-(3)H]- and [19R-(3)H]-labeled 19-hydroxy derivatives 2 and 5, were synthesized through NaB(3)H(4) reduction of the corresponding 19-aldehydes 3 and 6 as a key reaction. The hitherto unknown stereochemistry of the NaB(3)H(4) reduction was established based on the deuterium-labeling experiments with NaB(2)H(4). A comparison of (1)H-NMR spectra of the NaB(2)H(4) reduction products of 19-als