## 4 Discussion  
The chemical synthesis was performed under relatively mild reaction conditions. The use of CAN as an oxidant originated compound **5** in 34% yield [41]. In fact, and interestingly, in A-ring aromatic steroid derivatives, CAN leads to hydroxylation of the C9 benzyl atom and nitration of the C11 homobenzyl position [55]. The mechanism possibly involves the dehydration at C9-C11 followed by a nucleophilic addition at C11 and the formation of a radical at C9, which reacts with cerium (IV) to form a carbon cation, which can react with a second nucleophile, giving rise to hydroxyl group [22]. Steroid **6** was synthesized (89% yield) by the successful transformation of estrone **E1** into \(\Delta^{9,11}\)-estrone **3** by DDQ, followed by its acetylation [39]. Dehydrogenation using DDQ is widely used to obtain aromatic and \(\alpha,\beta\)-unsaturated carbonyls. The mechanism includes the hydride transfer to the quinone oxygen with the formation of a carbocation in the substrate, followed by the transference of a proton to the phenolate ion and the concomitant formation of a double bond [56]. Isolated  
Figure 9: Predicted interactions of the best ranked and synthetized compounds **2** and **6**, with 179-HSD1 in 2D (panel **A** and **B**) and 3D (panel **B**). (**A**) Van der Waals interactions are displayed in light green, conventional hydrogen bonds in green, and alkyl and pi-alkyl in pink. Both compounds, as co-crystallized ligand DHT, present alkyl and pi-alkyl interactions with Pro187, Val143, and Leu149. (**B**) Van der Waals interactions are displayed in light green, conventional hydrogen bonds in green, and alkyl and pi-alkyl in pink. (**C**) 3D representation of overlapping of compound **2** (in turquoise) and **6** (in yellow) in the macromolecule binding pocket. or in situ formed dioxines have been used as oxidants because they are selective and can allow mild reaction conditions [57]. In this context, the hydroxylation of **E1** acetate by dimethyldioxirane enabled the selective oxyfunctionalization at C9\(\alpha\)[40], affording steroid **4** (55% yield). The reaction involves the in situ formation of dimethyldioxirane by the reaction of OxoneTM with acetone and subsequent oxidative attack involving the tertiary carbon. Concerning the cell viability studies and structure-activity relationship data, the introduction of a 9\(\alpha\) hydroxyl group to E1 acetate (compound **4**) did not enhance the antiproliferative activity in hormone-dependent cancer cells when compared with E1 acetate (compound **2**). However, this hydroxylation led to a higher antiproliferative activity against HepaRG cells (IC\({}_{50}\) = 32.04 uM) than observed with E1 acetate (compound **2**) and \(\Delta^{9,11}\)-E1 acetate (compound **6**). Interestingly, the existence of the 11\(\beta\)-nitrooxy group, in addition to the 9\(\alpha\)-hydroxyl (compound **5**), markedly increased the antiproliferative effect against all cell types studied (Table 1). These are relevant results because in literature, in vitro studies for compounds **4** and **5** are not known to our knowledge. However, it was already evidenced that 11-nitrates of 9\(\alpha\),11\(\beta\)-dihydroxyacetylatrienes containing various substituents at positions 3 and 17 showed interesting antitumor activity in mongrel rats bearing a model of alveolar breast cancer [23]. In addition, stimulation of the tumor growth was observed after 15 days of treatment, probably due to the estrogenic effect inherent to steroidal molecules [23]. In addition, the 11\(\beta\)-nitrate of 17\(\alpha\)-ethylestradiol-3,17-diacetate also exhibited antiestrogen activity in an assay with the uterus of immature animals [58]. Our results for compound **5** showed an antiproliferative effect more pronounced in hormone-dependent cells (IC\({}_{50}\) = 5.87 uM for MCF-7 cells; IC\({}_{50}\) = 7.40 uM for T47-D cells; IC\({}_{50}\) = 5.30 uM for LNCaP cells).