Synthesis and evaluation of 2′-substituted 4-(4′-carboxy- or 4′-carboxymethylbenzylidene)-N-acylpiperidines:: Highly potent and in vivo active steroid 5α-reductase type 2 inhibitors

Sixteen compounds derived from N-acyl-4-benzylidenepiperidine-4'-carboxylic acids were synthesized and evaluated for inhibition of rat and human steroid 5alpha-reductase isozymes types 1 and 2. In the dicyclohexylacetyl series, fluorination in the 2-position of the benzene nucleus (15), exchange of the carboxy group by a carboxymethyl moiety (20), and combination of both structural modifications (25) led to highly active inhibitors of the human type 2 isozyme (IC50 values: 15, 11 nM; 20, 6 nM; 25, 7 nM; finasteride, 5 nM). In vivo all compounds tested markedly reduced the prostate weights in castrated testosterone-treated rats. Oral activity was shown for compound 7. From the finding that compound 15 is active in the rat, although it is a rather poor inhibitor of the rat enzyme and is a strong inhibitor of the human enzyme, it is concluded that it should be highly potent in men.