Improved Syntheses of Epristeride, a Potent Human 5.alpha.-Reductase Inhibitor

Two improved syntheses of a potent human 5 alpha-reductase inhibitor, epristeride, SK&F 105657, are described. The first synthesis starts from methyl 3-oxoandrost-4-ene-17 beta-carboxylate (1), which is converted to epristeride (5) in four synthetic steps in 44% overall yield. The second synthesis starts from commercially available 3-oxoandrost-4-en-17 beta-carboxylic acid (7), which is converted to epristeride (5) in two synthetic steps in 63% overall yield. Both syntheses are suitable for large scale production and have been employed to produce kilograms supplies of epristeride in high purity.