Recent Selected Publications




Carborane-Based Design of a Potent Vitamin D Receptor Agonist.
Otero R, Seoane S, Sigüeiro R, Belorusova A, Maestro M. A, Pérez-Fernández R, Rochel N, Mouriño A.
Chem. Sci. 2015, DOI: 10.1039/C5SC03084F
The Vitamin D nuclear receptor (VDR) is a potential target for cancer therapy. It is expressed in many tumors and its ligand shows anticancer actions. To combine these properties with the application of boron neutron capture therapy (BNCT), we design and synthetize a potent VDR agonist based on the skeleton of the hormone 1α,25-dihydroxyvitamin D3 (1,25D) and an o- arborane (dicarba-o-closo-1,2-dodecaborane) at the end of its side chain. The present ligand is the first secosteroidal analog with the carborane unit that efficiently binds to VDR and functions as an agonist with 1,25D-like potency in transcriptional assay on vitamin D target genes. Moreover it exhibits similar antiproliferative and pro-differentiating activities but is significantly less hypercalcemic than 1,25D. The crystal structure of its complex with VDR ligand binding domain reveals its binding mechanism involving boron-mediated dihydrogen bonds that mimic vitamin D hydroxylinteractions. In addition to the therapeutic interest, this study establishes the basis for the design of new unconventional vitamin D analogs containing carborane moieties for specific molecular recognition, and drug research and development.


Stereoselective Synthesis of 1b,25-Dihydroxyvitamin D3 and its 26,27-Hexadeuterated Derivative.
Loureiro J, Maestro M. A. Mouriño A, Sigüeiro R. 
J. Steroid Biochem. Mol. Biol. 2015, DOI: 10.1016/j.jsbmb.2015.09.007
A mild convergent synthesis of 1β,25-dihydroxyvitamin D3 (3a), a metabolite of vitamin D3, and its C26,27-hexadeuterated derivative (3b) are described. The A-ring and the CD-fragments are constructed from (R)-carvone and Inhoffen–Lythgoe diol, respectively. The triene system is assembled by a Pd(0)-catalyzed process, which involves an enol-triflate (A-ring fragment) and an alkenyl boronate (CD-side chain fragment). Deuterium labeling is introduced at the last step of the synthesis.


Novel 9-Alkyl- and 9-Alkylidene-substituted 1α,25-Dihydroxyvitamin D Analogues: Synthesis and Biological Examinations
Kulesza U, Plum L, Deluca H; Mouriño A, Sicinski R.
J. Med. Chem. 2015, 58, 6237-6247
Continuing the structure–activity relationship studies in the vitamin D area, we designed and synthesized novel C-9 substituted calcitriol analogues, possessing different nonpolar groups at this position. 9α-Methyl-1α,25-(OH)2D3, both epimers of 9-methylene-10,19-dihydro-1α,25-(OH)2D3 as well as the parent vitamin with the “reversed” triene system, 9-methylene-19-nor-1α,25-(OH)2D3, were obtained from the previtamin D precursors, constructed by either Suzuki–Miyaura, Sonogashira, or Stille couplings of the corresponding A- and C,D-ring fragments. An alternative synthetic path, leading to the latter vitamin and its homologue with 9-ethylidene group, involved formation of dienynes as precursors of the respective 19-norprevitamin D compounds. 9β-Methyl-19-nor-1α,25-(OHH)2D3 was prepared by homogeneous hydrogenation with Wilkinson catalyst, and this analogue was found to be the most active in vitro. Moreover, 9α-methyl-1α,25-(OH)2D3 and 9-methylene-19-nor-1α,25-(OH)2D3 showed some in vitro activity, however, the in vivo assays indicated only weak calcemic potency of these compounds in the intestinal calcium transport.


Pit-1 inhibits BRCA1 and sensitizes human breast tumors to cisplatin and vitamin D treatment
S. Seoane, E. AriaS, R. Sigueiro, J. Sendon-Lago, A. Martínez-Ordoñez, E. Castelao, N. Eiró, T. Garcia-Caballero, M. Macia, R. López-López, M. Maestro, F. Vizoso, A. Mouriño, Román Pérez-Fernández.
Oncotarget 2015, 6, 14456-71.
The POU class 1 homeobox 1 (POU1F1, also known as Pit-1), pertaining to the Pit-Oct-Unc (POU) family of transcription factors, has been related to tumor growth and metastasis in breast. However, its role in response to breast cancer therapy is unknown.
We found that Pit-1 down-regulated DNA-damage and repair genes, and specifically inhibited BRCA1 gene expression, sensitizing breast cancer cells to DNA-damage agents. Administration of 1α, 25-dihydroxy-3-epi-vitamin D3 (3-Epi, an endogenous low calcemic vitamin D metabolite) reduced Pit-1 expression, and synergized with cisplatin, thus, decreasing cell proliferation and apoptosis in vitro, and reducing tumor growth in vivo. In addition, fifteen primary cultures of human breast tumors showed significantly decreased proliferation when treated with 3-Epi+cisplatin, compared to cisplatin alone. This response positively correlated with Pit-1 levels.
Our findings demonstrate that high levels of Pit-1 and reduced BRCA1 levels increase breast cancer cell susceptibility to 3-Epi+cisplatin therapy.


Synthesis and Biological Activity of Two C-7 Methyl Analogues of Vitamin D
K. Sokolowska, D. Carballa, S. Seoane, R. Pérez-Fernández, A. Mouriño, R. Sicinski.
J. Org. Chem. 2015, 80, 165-173.
Two novel vitamin D analogues of the hormone 1a,25-(OH)2D3 modified at C-7, namely, 7-methyl-1a,25-(OH)2D3 (12) and 7-methyl-1a,25-(OH)2-19-nor-D3 (26) were synthesized and biologically evaluated to gain further insights into the structure-function relationships of vitamin D. Key steps in the synthesis of 12 include the functionalization at C-7 by an efficient regioselective hydrostannylation of an allene precursor, and the construction of the triene framework by a palladium-catalyzed intramolecular cyclization-Suzuki-Miyaura coupling cascade. Since the calcitriol analogue 12 was prone to conversion into its previtamin D form by thermal equilibration, the corresponding 19-nor-compound 26 was also synthesized. The diene moiety of compound 26 was constructed by a modified Julia coupling. UV data as well as X-ray analysis indicate that introduction of the methyl group at C-7 results in a significant deviation from planarity of the 5,7-diene moiety. The new vitamin D analogues 12 and 26 retained good VDR binding ability.


Synthesis of 9-Alkylated Calcitriol and Two 1a,25-Dihydroxy-9-methylene-10,19-dihydrovitamin D3 Analogs with Non-natural Triene System by Thermal Sigmatropic
U. Kulesza, R. Sigüeiro, A. Mouriño, R.R Sicinski.
J. Org. Chem. 2013, 78, 1444-1450.
1α,25-(OH)2-9á-Methylvitamin D3 (1), the first known analogue of the natural hormone 1α,25-(OH)2D3 with an alkyl substituent at C-9, and two 1α,25-(OH)2-9-methylene-10,19-dihydrovitamin D3 analogues (2) with an unprecedented non-natural triene system were synthesized by thermal isomerization of 1α,25-(OH)2-9-methylprevitamin D3 (3). Three alternative approaches (Sonogashira, Stille, or stereoselective dehydration of a tertiary propargyl alcohol) have been successfully used to construct the dienyne precursors of previtamin 6 possessing two methyl groups capable of participating in the [1,7]-sigmatropic hydrogen shift.


Synthesis and Biological Evaluation of 1α,25-Dihydroxyvitamin D3 Analogues with a Long Side Chain at C12 and Short C17 Side Chains
D.M. Carballa, S. Seoane, F. Zacconi, X. Pérez, A. Rumbo, S. Alvarez-Díaz, M.J. Larriba, R. Pérez-Fernández, A. Muñoz, M.A. Maestro, A. Mouriño, M. Torneiro  
J. Med. Chem. 2012, 55, 8642–8656.
Structure-guided optimization was used to design new analogues of 1α,25-dihydroxyvitamin D3 bearing the main side chain at C12 and a shorter second hydroxylated chain at C17. The new compounds 1ac were efficiently synthesized from the Inhoffen–Lythgoe diol. The triene system was introduced by the Pd-catalyzed tandem cyclization–Suzuki coupling method. The new analogues were assayed against human colon and breast cancer cell lines and in mice. All new vitamin D3 analogues bound less strongly to the VDR than 1α,25-dihydroxyvitamin D3 but had similar antiproliferative, pro-differentiating, and transcriptional activity as the native hormone. In vivo, the three analogues had markedly low calcemic effects.


Design, Synthesis, Evaluation and Structure of Vitamin D Analogues with Furan Side Chains.
R. Fraga, F. Zacconi, F. Sussman, P. Ordóñez-Morán, A. Muñoz, T. Huet, F. Molnár, D. Moras, N. Rochel, M. Maestro, A. Mouriño.
Chem. Eur. J. 2012, 18, 603-612
Based on the crystal structures of human VDR bound to 1,25D and superagonists ligands, four novel vitamin D analogues with aromatic furanic side chain(1a,b, 2a,b) were designed and synthesized. The triene system is constructed by an efficient stereoselective intramolecular cyclization of an enol triflate (A-ring precursor) followed by a Suzuki-Miyaura coupling of the resulting with an alkenyl boronic ester (CD-side chain upper fragment). The furanic side chains are constructed by gold chemistry. These analogues exhibit significant pro-differentiation effects and transactivation potency. The crystal structure of 3a in complex with the ligand.


Synhesis and Biological Evaluation of 1a,25-Dihydroxyvitamin D3 Analogues Hydroxymethylated at C-26
M. Regueira, S. Samanta, P.J. Malloy, P. Ordoñez-Moran, D. Resende, F. Sussman, A. Muñoz, A. Mouriño, Feldman D, M. Torneiro.
J. Med. Chem. 2011, 44, 3950-3962
Two novel analogues of 1α,25-dihydroxyvitamin D3 hydroxymethylated at C-26 (2 and 3) were designed by docking and synthesized. The syntheses were carried out by the convergent Wittig-Horner approach. The antiproliferative and transactivation potency of the compounds was evaluated in colon and breast cancer cell lines. The analogues showed a similar but reduced activity compared to 1,25(OH)2D3. Analogue 3 was more potent than analogue 2, and in some assays it exhibited potency similar to that of the natural ligand.


Crystal Structure of the Vitamin D Receptor Complexed to its Natural Metabolite 1,25-Dihydroxy-3-epi-vitamin D3.
F. Molnar, R. Sigüeiro, Y. Sato, C. Araujo, I. Schuster, P. P. Anthony P, Peluso, C. Muller, A. Mouriño, D. Moras, N. Rochel.
PLoS ONE. 2011, 66, e18124
In this study an effective synthesis of the 3-epimer of the 1α,25(OH)2D3 is described. The crystal structure of its complex with the human VDR-LBD is resolved. This natural metabolite displays specific adaptation of the ligand-binding pocket, as the 3-epimer maintains the number of hydrogen bonds by an alternative water-mediated interaction to compensate the abolished interaction with Ser278. In addition, the biological activity of the 1α,25(OH)2-3-epi-D3 in primary human keratinocytes and biochemical properties are comparable to 1α,25(OH)2D3. The physiological role of this pathway as the specific biological action of the 3-epimer remains unclear. However, its high metabolic stability together with its significant biologic activity makes this natural metabolite an interesting ligand for clinical applications. Our new findings contribute to a better understanding at molecular level how natural metabolites of 1α,25(OH)2D3 lead to significant activity in biological systems and we conclude that the C3-epimerization pathway produces an active metabolite with similar biochemical and biological properties to those of the 1α,25(OH)2D3.


An Expeditious Route to 1,25-Dihydroxyvitamin D3 and Analogs via Aqueous Tandem Palladium Catalyzed A-Ring Closure and Suzuki Coupling with C/D Unit.                          
Pranjal Gogoi, Rita Sigüeiro, Silvina Eduardo and Antonio Mouriño.
Chem. Eur. J. 2010, 16, 1432-1435.
A concise, general and stereoselective entry to the vitamin D triene system of the natural hormone 1,25D and six representative analogues, has been achieved by an efficient strategy featuring a highly stereoselective intramolecular cyclization of an enol triflate (A-ring or lower fragment) followed in situ by a Suzuki-Miyaura coupling of the resulting palladium intermediate with an alkenyl boronic ester (CD-side chain upper fragment). The method employs equimolar quantities of both fragments under protic conditions and can be used for the preparation of small amounts of new vitamin D analogues for biological testing. Further synthetic studies pertaining to even more challenging vitamin D analogues are underway in our laboratory.


Structure-Function Relationship and Crystal Structures of the Vitamin D Receptor Bound 2-Methyl-20S,23S)- and 2-Methyl–( 20S,23R)-epoxymethano-1,25-dihydroxyvitamin D
Pierre Antony, Rita Sigüeiro, Tiphaine Huet, Pierre Antony, Yoshiteru Sato, Nick Ramalanjaona, Luis Cezar Rodrigues, Antonio Mouriño, Dino Moras, Natacha Rochel.
J. Med. Chem. 2010, 53, 1159-1171


The Vitamin D nuclear receptor is a ligand-dependent transcription factor that controls multiple biological responses such as cellular proliferation, immune responses and bone mineralization. Numerous 1,25D analogues, which exhibit low calcemic side effects and/or anti-tumoral properties, have been synthesized. We recently showed that the synthetic analogue (20S,23S)-epoxymethane-1,25-D (2a) acts as a 1,25D superagonist and exhibits both anti-proliferative and pro-differentiating properties in vitro. Using this information and based on the crystal structures of human VDR ligand binding domain (hVDR LBD) bound to 1,25D, 2α-methyl-1,25D or 2a, we designed a novel analogue, 2α-methyl-(20S,23S)-epoxymethane-1,25D (4a), in order to increase its transactivation potency. Here, we solved the crystal structures of the hVDR LBD in complex with the 4a (C23S) and its epimer 4b (C23R) and determined their correlation with specific biological outcomes.


Synthesis of 25-HydroxyvitaminD3and 26,26,26,27,27,27-Hexadeutero-25-hydroxyvitaminD3on Solid Support.
Daniel Nicoletti, Antonio Mourinño, and Mercedes Torneiro.
J. Org. Chem. 2009, 74, 4782-4786


A convenient five-step route to 25-hydroxylated vitamin D3compounds on (hydroxymethyl)polystyrene support is reported. A CD-side chain fragment was anchored to the solid phase through an ester group at C25 and coupled to an A ring building block to assemble the vitamin D triene system by the Wittig-Horner approach. Deprotection of the hydroxy group was carried out on the support, prior to functionalization at C25. The title compounds were released from the resin in excellent global yield by nucleophilic attack on the ester carbonyl group using commercially available organometallic reagents. This key last step offers an opportunity for the efficient generation of 26,27-labeled compounds and also for diversification at the side chain without need for a pool of side chain fragments.


Structure-Based Design of a Superagonist Ligand for the Nuclear Receptor of Vitamin D.
Hourai S, Rodrigues LC, Antony P, Reina-San-Martin B, Ciesielski F, Magnier B, Schoonjans K, Mouriño A, Rochel  N, Moras D.
Chem. Biol. 2008, 15, 383-392.


The plethora of actions of the natural hormona 1,25-dihydroxyvitamin D3 (1,25D) in various physiological processes suggest wide clinical applications for the vitamin D nuclear receptor (VDR). Based on the crystal structures of human VDR bound to 1,25D and to the superagonist KH1060, we designed the new superagonistic ligand AMCR277A, which incorporates a tetrahydrofurane ring in the aliphatic side chaín to avoid an entropic loss while taking advantage of different paths observed in superagonist activity. The crystal structure provides an explanation of the mechanism of superagonist activity and a rational approach to the design of more potent ligands.


Synthesis and Conformational Analysis of New 17a,21-Cyclo-22-Unsaturated Analogues of Calcitriol.
Ricardo Riveiros, Antonio Rumbo, Luis Sarandeses, Antonio Mouriño.
J. Org. Chem. 2007, 72, 5777-5485.


Six new calcitriol analogues, conformationally restricted at their side chain by the introduction of both a cyclopropane ring at C17-C20 and a double or triple bond at C22, were synthesized using the Wittig- Horner approach to construct the triene system. The six CD-ring and side-chain bearing fragments were prepared from ketone 14 by a divergent route to generate both series of epimers at C20, followed by stereoselective cyclopropanation. The (E)-alkenyl side chain was synthesized by means of a Wittig reaction. The alkynyl side chain was prepared by Corey-Fuchs homologation, followed by alkylation. The (Z)- alkenyl side chain was prepared from the previous alkyne by partial hydrogenation. The 20-epi analogues bind more strongly to VDR than the corresponding analogues with the C20 natural stereochemistry. These results can be reasoned by conformational analysis and hydrophobic interactions with the VDR ligand-binding domain.  


Novel 1,25-Dihydroxyvitamin D3Analogues with the Side Chain at C12
Xosé González-Avión, Antonio Mouriño, Natacha Rochel, and Dino Moras
J. Med. Chem. 2006, 49, 1409-1516


The plethora of actions of 1,25Din various systems suggested wide clinical applications of vitamin D nuclear receptor (VDR) ligands in treatments of inflammation, dermatological indication, osteoporosis, cancers, and autoimmune diseases. More than 3000 vitamin D analogues have been synthesized in order to reduce the calcemic side effects while maintaining the transactivation potency of the natural ligand. In light of the crystal structures of the vitamin D nuclear receptor (VDR), novel analogues of the hormone 1,25Dwith side chains attached to C-12 were synthesized via the convergent Wittig-Horner approach. Among the compounds studied, the analogue 2b showed the highest binding affinity for VDR and was the most potent at inducing VDR transcriptional activity in a transient transfection assay (20% of the transactivation activity of the natural ligand.


Pd-Catalyzed CarbocyclizationNegishi Cross-Coupling Cascade: A Novel Approach to 1,25-Dihydroxyvitamin D3and Analogues.
Clara Gómez-Reino, Cristian Vitale, Miguel Maestro, and Antonio Mouriño.
Org. Lett. 2005, 7, 5885-5887


A mild palladium-catalyzed cascade has been used for the synthesis of the hormone 1,25-dihydroxyvitamin D3 (calcitriol, 1a) and its analogues 1b and 1c. This one-pot process involves two consecutive transformations at room temperature: An initial palladium-catalyzed 6-exo-cyclocarbopalladation of vinyl triflates followed by a Negishi cross-coupling reaction with an alkenyl zinc. This novel strategy opens new possibilities for the preparation of a variety of new vitamin D analogues of therapeutic potential, particularly with modifications at the triene and/or ring-A.


The First Locked Side-Chain Analogues of Calcitriol (1,25-Dihydroxyvitamin D3) Induce Vitamin D Receptor Transcriptional Activity
Xenxo Pérez-García, Antonio Rumbo, María Jesús Larriba, Paloma Ordóñez, Alberto Muñoz, and Antonio Mouriño.
Org. Lett. 2003, 5, 4033-4036


We describe the synthesis of the first locked side-chain analogues of the natural hormone 1,25-Dand their effects on gene transcription in human colon cancer cells. Analogue 2 was more potent than 1,25-Dat inducing vitamin D receptor (VDR) transcriptional activity. Analogues 3a and 3b show potency similar to that of 1,25-D, whereas 3c was less active. The novel analogues efficiently bind VDR in vivo to induce transcription from a consensus vitamin D responsive element (VDRE).


Functionalization at C-12 of 1,25-Dihydroxyvitamin D3Strongly Modulates the Affinity for the Vitamin D Receptor (VDR)
Xosé́ C. González-Avión and Antonio Mouriño.
Org. Lett. 2003, 5, 2291-2293


The first synthesis of analogues of the natural hormone 1,25-D(1a) with substituents at C-12 is reported. The following are the relative affinities of the novel compounds for the vitamin D receptor (VDR) compared to that of 1a (100%): (1b, 1%), (1c, 50%), and (1d, 440%).