Improved synthesis of EM-1745, preparation of its C17-ketone analogue and comparison of their inhibitory potency on 17beta-hydroxysteroid dehydrogenase type 1.

Endocrine therapies are widely used for the treatment of estrogen-sensitive diseases. 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1) is involved in the last step of the biosynthesis of potent estrogen estradiol (E(2)). This enzyme catalyzes the reduction of the C17-ketosteroid estrone (E(1)) into the C17beta-hydroxy steroid E(2) using the cofactor NAD(P)H. The X-ray analysis of E(2)/adenosine bisubstrate inhibitor EM-1745 proven that this compound interacts with both the substrate- and the cofactor-binding sites. However, E(1) is a better substrate of 17beta-HSD1 than E(2). Thus, in order to improve the inhibitory potency of EM-1745, the C17-ketone analogue was prepared. During this work, a new and more efficient method for synthesizing EM-1745 was developed using an esterification and a cross-metathesis as key steps. Contrary to what was expected, the C17-ketone analogue of EM-1745 is a less potent inhibitor (IC(50) = 12 nM) than the C17-alcohol (IC(50) = 4 nM) in homogenated HEK-293 cells overexpressing 17beta-HSD1. Our results contribute to the knowledge of an unexpected observation: the C17-ketone steroidal inhibitors of 17beta-HSD1 are less potent than their corresponding C17-alcohol derivatives.