Synthesis and preliminary evaluation of a modified estradiol-core bearing a fused γ-lactone as non-estrogenic inhibitor of 17β-hydroxysteroid dehydrogenase type 1

Impact of structural modifications at positions 13, 16 and 17 of 16β-(m-carbamoylbenzyl)-estradiol on 17β-hydroxysteroid dehydrogenase type 1 inhibition and estrogenic activity

The chemical synthesis of four stereoisomers (compounds 5a-d) of 16β-(m-carbamoylbenzyl)-estradiol, a potent reversible inhibitor of 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1), and two intermediates (compounds 3a and b) was performed. Assignment of all nuclear magnetic resonance signals confirmed the stereochemistry at positions 13, 16 and 17. Nuclear overhauser effects showed clear correlations supporting a C-ring chair conformation for 5a and b and a C-ring boat conformation for 5c and d. These compounds were tested as 17β-HSD1 inhibitors and to assess their proliferative activity on estrogen-sensitive breast cancer cells (T-47D) and androgen-sensitive prostate cancer cells (LAPC-4). Steroid derivative 5a showed the best inhibitory activity for the transformation of estrone to estradiol (95, 82 and 27%, at 10, 1 and 0.1μM, respectively), but like the other isomers 5c and d, it was found to be estrogenic. The intermediate 3a, however, was weakly estrogenic at 1μM, not at all at 0.1μM, and showed an interesting inhibitory potency on 17β-HSD1 (90, 59 and 22%, at 10, 1 and 0.1μM, respectively). As expected, no compound showed an androgenic activity. The binding modes for compounds 3a and b, 5a-d and CC-156 were evaluated from molecular modeling. While the non-polar interactions were conserved for all the inhibitors in their binding to 17β-HSD1, differences in polar interactions and in binding conformational energies correlated to the inhibitory potencies.

Chemical synthesis, characterisation and biological evaluation of lactonic-estradiol derivatives as inhibitors of 17β-hydroxysteroid dehydrogenase type 1

To control estradiol (E2) formation, we are interested in synthesizing inhibitors of 17β-hydroxyteroid dehydrogenase type 1 (17β-HSD1). Since the results of docking experiments have shown that E2-lactone derivatives substituted in position 19 or 20 (E-ring) could generate interactions with the active site of the enzyme, we carried out their chemical synthesis. After having prepared the 16β,17β-γ-lactone-E2 in four steps starting from estrone (E1), we introduced the molecular diversity by adding a hydroxymethyl, a methylcarboxylate, a carboxy or an allyl group. The allyl derivative was used as a key intermediate to generate a hydroxyethyl side chain in α or β position. Two lactols were also obtained from two hydroxyalkyl lactones. Enzymatic assays revealed that lactone and lactol derivatives weakly inhibited 17β-HSD1 in homogenized HEK-293 cells overexpressing 17β-HSD1 (34-60% at 1 μM) and in intact T-47D cells expressing 17β-HSD1 (10-40% at 10 μM). This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".