Synthesis of novel 17-triazolyl-androst-5-en-3-ol epimers via Cu(I)-catalyzed azide-alkyne cycloaddition and their inhibitory effect on 17α-hydroxylase/C17,20-lyase

The regioselective Cu(I)-catalyzed 1,3-dipolar cycloaddition of 17 alpha- and 17 beta-azidoandrost-5-en-3 beta-ol epimers (3b and 5b) with different terminal alkynes afforded novel 1,4-substituted triazolyl derivatives (8a-k and 9a-k). For the preparation of 5'-iodo-l',2',3'-triazoles (8m-n and 9m-n), an improved method was developed, directly from steroidal azides and terminal alkynes, in reaction mediated by Cul and IC1 as iodinating agents. Acetolysis and subsequent hydrolysis of 8n and 9n yielded 5'-hydroxy-l',2',3'-triazoles 8o and 9o. The inhibitory effect of 8a-o, 9a-o, 3, and 5 on rat testicular C-17,C-20-lyase was investigated by means of an in vitro radioincubation technique. The results revealed that the C-17 epimers of steroidal triazoles influence the C-17,C-20-lyase effect. Inhibitors were found only in the 17 alpha-triazolyl series (8a-o), whereas in the C-17 azide pair the 17 beta compound (5b) was more potent.