Total Synthesis of the Proposed Structure of Penasulfate A: l-Arabinose as a Source of Chirality

The total synthesis of putative penasulfate A was effectively achieved by a convergent strategy with a longest linear sequence of 14 steps and overall yield of 8.6%. The highlights of our strategy involved an E-selective olefin cross-metathesis, Suzuki cross-coupling, and a copper(I)-catalyzed coupling reaction.

Inhibitors of 17β-hydroxysteroid dehydrogenase type 1, 2 and 14: Structures, biological activities and future challenges

During the past 25 years, the modulation of estrogen action by inhibition of 17β-hydroxysteroid dehydrogenase types 1 and 2 (17β-HSD1 and 17β-HSD2), respectively, has been pursued intensively. In the search for novel treatment options for estrogen-dependent diseases (EDD) and in order to explore estrogenic signaling pathways, a large number of steroidal and nonsteroidal inhibitors of these enzymes has been described in the literature. The present review gives a survey on the development of inhibitor classes as well as the structural formulas and biological properties of their most interesting representatives. In addition, rationally designed dual inhibitors of both 17β-HSD1 and steroid sulfatase (STS) as well as the first inhibitors of 17β-HSD14 are covered.

Pd-catalyzed steroid reactions

We review the most important achievements of the last decade in the field of steroid synthesis in the presence of palladium catalysts. Various palladium-catalyzed cross-coupling reactions, including Heck, Suzuki, Stille, Sonogashira, Negishi and others, are exemplified with steroid transformations.

Progesterone-adenine hybrids as bivalent inhibitors of P-glycoprotein-mediated multidrug efflux: design, synthesis, characterization and biological evaluation

Bivalent ligands were designed on the basis of the described close proximity of the ATP-site and the putative steroid-binding site of P-glycoprotein (ABCB1). The syntheses of 19 progesterone-adenine hybrids are described. Their abilities to inhibit P-glycoprotein-mediated daunorubicin efflux in K562/R7 human leukemic cells overexpressing P-glycoprotein were evaluated versus progesterone. The hybrid with a hexamethylene linker chain showed the best inhibitory potency. The efficiency of these progesterone-adenine hybrids depends on two main factors: (i) the nature of the linker and (ii) its attachment point on the steroid skeleton.

Application of olefin metathesis in the synthesis of steroids

Over the past decade, ruthenium-mediated metathesis transformations, including cross-metathesis, ring-closing metathesis, enyne metathesis, ring-opening metathesis polymerization, and also tandem processes, belong to the most intensively studied reactions. Many applications of olefin metathesis in the synthesis of natural products have been recently described. Also in the field of steroid chemistry new methods of total synthesis and hemisynthesis based on metathesis reactions have been elaborated. Various biologically active compounds, e.g. vitamin D and hormone analogues, steroid dimers and macrocycles, etc. have been prepared using a variety of olefin-metathesis protocols.

Contribution to the development of inhibitors of 17β-hydroxysteroid dehydrogenase types 1 and 7: key tools for studying and treating estrogen-dependent diseases

17β-Hydroxysteroid dehydrogenases (17β-HSDs) belong to a group of key enzymes involved in the biosynthesis of steroidal hormones by catalyzing the reduction of 17-ketosteroids or the oxidation of 17β-hydroxysteroids. From three members known in the early nineties, the 17β-HSD functional family has grown to 15 members over the last 20 years. This growing number of 17β-HSD isoforms questioned the importance of each member, especially in their implication in estrogen- and androgen-dependent diseases, such as breast and prostate cancers. One of the strategies used to address the physiological importance of 17β-HSDs is to use potent and selective inhibitors. Furthermore, enzyme inhibitors could also be of therapeutic interest by reducing the level of estradiol (E2). Focusing on estrogens, we targeted 17β-HSD types 1 and 7, two enzymes able to transform the weak estrogen estrone (E1) into the potent estrogen E2. The present review article gives a description of different classes of inhibitors of 17β-HSD1 (C6-derivatives of E2, C16-derivatives of E2 as alkylating and dual action compounds, E2-adenosine hybrids, E2-simplified adenosine hybrids, and C16-derivatives of E1 or E2) and of inhibitors of 17β-HSD7, all these inhibitors developed in our laboratory. The chemical structures and inhibitory activity of these steroidal inhibitors, their potential as therapeutic agents, and their use as tools to elucidate the role of these enzymes in particular biological systems will be discussed. Article from the Special issue on Targeted Inhibitors.

17β-Hydroxysteroid dehydrogenases (17β-HSDs) as therapeutic targets: protein structures, functions, and recent progress in inhibitor development

17β-Hydroxysteroid dehydrogenases (17β-HSDs) are oxidoreductases, which play a key role in estrogen and androgen steroid metabolism by catalyzing final steps of the steroid biosynthesis. Up to now, 14 different subtypes have been identified in mammals, which catalyze NAD(P)H or NAD(P)(+) dependent reductions/oxidations at the 17-position of the steroid. Depending on their reductive or oxidative activities, they modulate the intracellular concentration of inactive and active steroids. As the genomic mechanism of steroid action involves binding to a steroid nuclear receptor, 17β-HSDs act like pre-receptor molecular switches. 17β-HSDs are thus key enzymes implicated in the different functions of the reproductive tissues in both males and females. The crucial role of estrogens and androgens in the genesis and development of hormone dependent diseases is well recognized. Considering the pivotal role of 17β-HSDs in steroid hormone modulation and their substrate specificity, these proteins are promising therapeutic targets for diseases like breast cancer, endometriosis, osteoporosis, and prostate cancer. The selective inhibition of the concerned enzymes might provide an effective treatment and a good alternative to the existing endocrine therapies. Herein, we give an overview of functional and structural aspects for the different 17β-HSDs. We focus on steroidal and non-steroidal inhibitors recently published for each subtype and report on existing animal models for the different 17β-HSDs and the respective diseases. Article from the Special issue on Targeted Inhibitors.

Preparation of 6beta-estradiol derivative libraries as bisubstrate inhibitors of 7beta-hydroxysteroid dehydrogenase type using the multidetachable sulfamate linker

Combinatorial chemistry is a powerful tool used to rapidly generate a large number of potentially biologically active compounds. In our goal to develop bisubstrate inhibitors of 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1) that interact with both the substrate (estrone or estradiol) and the cofactor (NAD(P)H) binding sites, we used parallel solid-phase synthesis to prepare three libraries of 16beta-estradiol derivatives with two or three levels of molecular diversity. From estrone, we first synthesized a sulfamate precursor that we loaded on trityl chloride resin using the efficient multidetachable sulfamate linker strategy recently developed in our laboratory. We then introduced molecular diversity [one or two amino acid(s) followed by a carboxylic acid] on steroid nucleus by Fmoc peptide chemistry. Finally, after a nucleophilic cleavage, libraries of 30, 63 and 25 estradiol derivatives were provided. A library of 30 sulfamoylated estradiol derivatives was also generated by acidic cleavage and its members were screened for inhibition of steroid sulfatase. Biological evaluation on homogenated HEK-293 cells overexpressing 17beta-HSD1 of the estradiol derivatives carrying different oligoamide-type chains at C-16 first revealed that three levels of molecular diversity (a spacer of two amino acids) were necessary to interact with the adenosine part of the cofactor binding site. Second, the best inhibition was obtained when hydrophobic residues (phenylalanine) were used as building blocks.