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Vitamin D receptor ligands have potential for the treatment of hyperproliferative diseases and disorders related to the immune system. However, hypercalcemic effects limit their therapeutical uses and call for the development of tissue‐selective new analogs. We have designed and synthesized the first examples of 1α,25‐dihydroxyvitamin D3 analogs bearing an allenic unit attached to the D ring to restrict the side‐chain conformational mobility. The triene system was constructed by a Pd0‐mediated cyclization/Suzuki‐Miyaura cross‐coupling process in the presence of an allenic side chain. The allenic moiety was built through an orthoester‐Claisen rearrangement of a propargylic alcohol. The biological activity and structure of (22S)‐1α,25‐dihydroxy‐17,20‐dien‐24‐homo‐21‐nor‐vitamin D3 bound to binding domain of the vitamin D receptor, provide information concerning side‐chain conformational requirements for biological activity., Looking for side‐chain conformational requirements of vitamin D analogs for selective biological activity, a new active vitamin D analog that has conformationally restricted mobility at the side chain and adopts a similar structure than the natural hormone 1α,25‐dihydroxyvitamin D3 in the binding pocket was designed by docking and synthesized. The highlights of the synthesis include a Pd0‐catalyzed cascade and an orthoester‐Claisen‐rearrangement for the formation of the trienic system and the allenic side‐chain, respectively.

The toxic calcemic effects of the natural hormone 1α,25-dihydroxyvitamin D

An efficient Lewis acid-assisted asymmetric carbonyl-ene reaction to set the 1α-hydroxyl functionality of enol-triflate, precursor of the A-ring of the hormone calcitriol and its 1α-hydroxyderivatives, is described. The secondary parallel hypercalcemic effects associated with the treatment of several hyperproliferative diseases with the natural hormone 1α,25-dihydroxyvitamin D3 (calcitriol) and/or known active vitamin D metabolites and analogs, demand the development of efficient and rapid methods for the preparation of vitamin D receptor (VDR) ligands as new selective and non-calcemic agonists. Here we describe an efficient and adaptable multigram-scale synthetic sequence to access an A-ring synthon as useful precursor of the vitamin D triene system of 1α-hydroxylated vitamin D derivatives via Pd-catalyzed carbocyclization/Suzuki–Miyaura cross-coupling reactions in a protic medium. The key step is an asymmetric Lewis acid-promoted carbonyl-ene reaction to a chiral glyosylate ester to establish the 1α-hydroxyl group of 1α,25-dihydroxyvitamin D3 and its derivatives This research was funded by ENDOTHERM GmbH, Xunta de Galicia (GRC/ED431B/20) and the University of Santiago de Compostela (Spain) SI

International audience; A high number of biologically active and low-calcemic secosteroidal ligands of the vitamin D receptor (VDR) have been developed, some of which are already used clinically although with limited success in the treatment of hyperproliferative diseases because the required pharmaceutical dosages induce toxicity. We describe here the in silico design, synthesis, structural analysis and biological evaluation of two novel active lithocholic acid derivatives hydroxylated at the side chain as highly potent inhibitors of atopic dermatitis-relevant keratinocyte inflammation of potential therapeutic interest.

International audience; New adjuvant formulations, based on proteoliposomes b40 nm and cochleates b100 nm, without Al(OH)3 adjuvant, were evaluated regarding their ability to generate Th1 immune response through a Delayed -Type Hypersensitivity Test, at the mouse model, by using a Neisseria meningitidis B protein complex as antigen. The formulations were administered by intramuscular (IM) (2 inoculations - at baseline and after 14 days) and intranasal (IN) (3 inoculations at 7 days) immunization pathways. All IM immunized groups were able to induce similar response to these formulations as well as to VA-MENGOC-BC® vaccine - containing Al(OH)3 adjuvant (used as positive control of the trial). In all groups, the induced inflammation (IP) rate was statistically higher than in the negative control group (CN) (p b 0.05). Immunogenicity, measured by HSR and CD4+ lymphocyte increase was equivalent to the control vaccine and most important, granuloma reactogenicity at the site of injection was eliminated, fact demonstrated by histological study. All groups of animals immunized by IN route showed HSR reactions and statistically significant differences with respect to the CN group. However, IP values were lower, with statistical differences (p b 0.05) for the same adjuvant formulation IM administered, except the AIF2-nCh formulation that generated statistically similar induction (p N 0.05) by both immunization pathways, suggesting it to be the best candidate for the next IN trial. Proteoliposome and cochleate formulations tested were able to mount potent Th-1 immune response, equivalent to the original vaccine formulation, with the advantage of less reactogenicity in the site of the injection, caused by the toxicity of Al(OH)3 adjuvant gel.

The hypercalcemic effects of the hormone 1α,25-dihydroxyvitamin D3 (calcitriol) and most of known vitamin D metabolites and analogs call for the development of non secosteroidal vitamin D receptor (VDR) ligands as new selective and noncalcemic agonists for treatment of hyperproliferative diseases. We report on the in silico design and stereoselective synthesis of six lithocholic acid derivatives as well as on the calcemic activity of a potent LCA derivative and its crystallographic structure in complex with zVDR LBD. The low calcemic activity of this compound in comparison with the native hormone makes it of potential therapeutic value. Structure-function relationships provide the basis for the development of even more potent and selective lithocholic acid-based VDR ligands.

Both 25R- and 25S-25-adamantyl-23-yne-26,27-dinor-1α,25-dihydroxyvitamin D3 (4a and 4b) were stereoselectively synthesized by a Pd(0)-catalyzed ring closure and Suzuki–Miyaura coupling between enol-triflate 7 and alkenyl-boronic ester 8. The 25S isomer (4b) showed high vitamin D receptor (VDR) affinity (50% of that of the natural hormone 1α,25-dihydroxyvitamin D3, 1) and transactivation potency (kidney HEK293, 90%). In endogenous gene expression, it showed high cell-type selectivity for kidney cells (HEK293, CYP24A1 160% of 1), bone cells (MG63, osteocalcin 64%), and monocytes (U937, CAMP 96%) over intestine (SW480, CYP24A1 8%) and skin (HaCaT, CYP24A1 7%) cells. The X-ray crystal structural analysis of 4b in complex with rat VDR-ligand binding domain (LBD) showed the highest Cα positional shift from the 1/VDR-LBD complex at helix 11. Helix 11 of the 4b and 1 VDR-LBD complexes also showed significant differences in surface properties. These results suggest that 4b should be examined further as another can...

A convergent synthesis of side-chain locked vitamin D analogs 3 and 4, which bind strongly in silico to the vitamin D receptor (VDR), is described. The synthetic approach features an SN2'- syn displacement of carbamates by cuprates to set the challenging quaternary stereogenic center at C17 and a Pd-catalyzed construction of the triene system in the presence of a diyne moiety.

We describe an efficient convergent synthesis of vitamin D3 metabolites and analogues. The synthetic strategy relies on a tandem Pd-catalyzed A-ring closure and Suzuki-Miyaura coupling to the CD-side chain component to set directly the vitamin D triene system under protic conditions. This strategy enables rapid access to vitamin D3 and 3-epi-vitamin D3 metabolites and analogues modified at the side chain for biological evaluation and structural and metabolic studies.

Herein, we describe a synthetic strategy to access 1α,25-dihydroxyvitamin D3 (calcitriol) analogs with natural or unnatural configuration at C20 and unsaturation at the D-ring. The synthetic approach is exemplified by the synthesis of two potent analogs, namely 1α,25-dihydroxy-16-en-23-yne-vitamin D3 and 1α,25-dihydroxy-20-epi-24a-homo-26,27-dimethyl-vitamin D3. A key feature of the synthetic strategy is the generation of an unnatural configuration at C20 by a catalytic asymmetric reduction of an α,β,γ,δ-unsaturated ester with the CuH species in a micellar system.

As part of our program on synthesis of labeled vitamin D metabolites and analogs, we describe here an efficient and versatile synthetic approach to 28,28,28-trideutero- 25-hydroxydihydrotachysterol2 where isotopic labeling was incorporated stereoselectively in the last step of the synthesis. This deuterated compound will allow the study this analog in vitro or in vivo and to measure AT10-like compounds in serum by LC-MS/MS.

A convergent approach to 25S,26-dihydroxyvitamin D3 (1) has been developed in our laboratories. The A-ring and the CD-fragment are constructed from ergocalciferol and Inhoffen-Lythgoe diol, respectively. The triene system is assembled by a Wittig-Horner coupling. With this convergent synthesis, a novel hydroxylated vitamin D metabolite in our laboratory is available for biological testing.

Herein, we describe a versatile and efficient total synthesis of 1α,25-dihydroxyvitamin D3 (calcitriol). The synthetic strategy relies on an unprecedented Si-assisted SN2′-syn displacement of carbamates by cuprates to set the challenging pivotal quaternary methyl group at the fused-ring junction of the CD-trans-hydrindane core. Other key transformations involve the catalytic asymmetric reduction of an α,β,γ,δ-unsaturated ester with CuH to generate the natural steroidal configuration at C20 and a Pauson–Khand cyclization to form the CD-ring skeleton. This strategy enables the syntheses of novel analogs for structure-function studies and drug development.

A new approach to 19-nor-A-ring phosphine oxide 5 together with a convergent synthesis of the vitamin D3 analogue 1α,25-dihydroxy-19-norvitamin D3 (3) have been developed. The 19-nor-A-ring is constructed from (S)-carvone. The triene system is assembled by a Wittig-Horner coupling.

As part of our program on synthesis of labeled vitamin D metabolites and analogs, we describe here an efficient and versatile synthetic approach to 28,28,28-trideutero- 25-hydroxydihydrotachysterol

Both 25 R- and 25 S-25-adamantyl-23-yne-26,27-dinor-1α,25-dihydroxyvitamin D

International audience; We report the design, synthesis, biological evaluation, and structural analysis of a new class of vitamin D analogues that possess an aromatic m-phenylene D-ring and an alkyl chain replacing the C-ring. A key feature of the synthetic strategy is a stereoselective Pd-catalyzed construction of the triene system in aqueous medium that allows the rapid preparation of small amounts of VDR ligands for biological screening. Analogues with the shorter (2a) and longer (2d, 2e) side chains attached to the triene system have no calcemic activity. Compound 2a binds to VDR with the same order of magnitude than calcipotriol and oxacalcitriol. It also reduces proliferation in normal and tumor cells similarly to the natural hormone 1α,25-dihydroxyvitamin D3, calcipotriol, and oxacalcitriol, suggesting preclinical studies related to hyperproliferative disorders such as psoriasis and cancer.

A convergent synthesis of side-chain locked vitamin D analogs 3 and 4, which bind strongly in silico to the vitamin D receptor (VDR), is described. The synthetic approach features an S

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-(OH)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.

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.

We describe an efficient convergent synthesis of vitamin D

Herein, we describe a synthetic strategy to access 1α,25-dihydroxyvitamin D3 (calcitriol) analogs with natural or unnatural configuration at C20 and unsaturation at the D-ring. The synthetic approach is exemplified by the synthesis of two potent analogs, namely 1α,25-dihydroxy-16-en-23-yne-vitamin D3 and 1α,25-dihydroxy-20-epi-24a-homo-26,27-dimethyl-vitamin D3. A key feature of the synthetic strategy is the generation of an unnatural configuration at C20 by a catalytic asymmetric reduction of an α,β,γ,δ-unsaturated ester with the CuH species in a micellar system.

A convergent approach to 25S,26-dihydroxyvitamin D

The first synthesis of 1α,25-dihydroxy-3-epi-vitamin D2 is described. Key steps of the synthesis entail the construction of the triene unit by a Pd-catalyzed ring closure of an enol-triflate (A-ring fragment) followed by a Suzuki–Miyaura coupling with a boronate (upper fragment), and the installation of the methyl group at C-24 by an SN2′-syn displacement of an allylic carbamate. This article is part of a Special Issue entitled ‘SI:17th Vitamin D Workshop’.

3-epi-1α,25-dihydroxyvitamin D3 (3-epi-1α,25(OH) 2D3), a natural metabolite of 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3), exhibits potent vitamin D receptor (VDR)-mediated actions such as inhibition of keratinocyte growth or suppression of parathyroid hormone secretion. These VDR-mediated actions of 3-epi-1α,25(OH)2D3 needed an explanation as 3-epi-1α,25(OH)2D3, unlike 1α,25(OH) 2D3, exhibits low affinity towards VDR. Metabolic stability of 3-epi-1α,25(OH)2D3 over 1α,25(OH)2D3 has been hypothesized as a possible explanation. To provide further support for this hypothesis, we now performed comparative metabolism studies between 3-epi-1α,25(OH)2D 3 and 1α,25(OH)2D3 using both the technique of isolated rat kidney perfusion and purified rat CYP24A1 in a cell-free reconstituted system. For the first time, these studies resulted in the isolation and identification of 3-epi-calcitroic acid as the final inactive metabolite of 3-epi-1α,25(OH)2D3 produced by rat CYP24A1. Furthermore, under identical experimental conditions, it was noted that the amount of 3-epi-calcitroic acid produced from 3-epi-1α,25(OH) 2D3 is threefold less than that of calcitroic acid, the analogous final inactive metabolite produced from 1α,25(OH) 2D3. This key observation finally led us to conclude that the rate of overall side-chain oxidation of 3-epi-1α,25(OH) 2D3 by rat CYP24A1 leading to its final inactivation is slower than that of 1α,25(OH)2D3. To elucidate the mechanism responsible for this important finding, we performed a molecular docking analysis using the crystal structure of rat CYP24A1. Docking results suggest that 3-epi-1α,25(OH)2D3, unlike 1α,25(OH)2D3, binds to CYP24A1 in an alternate configuration that destabilizes the formation of the enzyme-substrate complex sufficiently to slow the rate at which 3-epi-1α,25(OH)2D 3 is inactivated by CYP24A1 through its metabolism into 3-epi-calcitroic acid. J. Cell. Biochem. 114: 2293-2305, 2013. © 2013 Wiley Periodicals, Inc. Copyright © 2013 Wiley Periodicals, Inc.

9-Alkylidene analogs of 19-nor-1α,25-(OH) 2 D 3 were synthesized, possessing a ‘reversed’ triene system compared to the natural hormone. The conjugated triene moiety of the novel analogs was constructed by coupling an enyne anion, representing an A-ring synthon, with a 9α-substituted Grundmann ketone derivative. Regioselective dehydration followed by semihydrogenation under Lindlar conditions, provided the desired 9-alkylated 19-norprevitamins which were thermally isomerized to the corresponding 9-methylene and 9-ethylidene analogs of 19-norcalcitriol. It was established that only the former compound had significant binding affinity to the full-length recombinant rat vitamin D receptor. The remaining in vitro studies show very low activity of both analogs. This article is part of a Special Issue entitled ‘Vitamin D Workshop’.

Automatic classification of news articles is a relevant problem due to the large amount of news generated every day, so it is crucial that these news are classified to allow for users to access to information of interest quickly and effectively. On the one hand, traditional classification systems represent documents as bag-of-words (BoW), which are oblivious to two problems of language: synonymy and polysemy. On the other hand, several authors propose the use of a bag-of-concepts (BoC) representation of documents, which tackles synonymy and polysemy. This paper shows the benefits of using a hybrid representation of documents to the classification of textual news, leveraging the advantages of both approaches—the traditional BoW representation and a BoC approach based on Wikipedia knowledge. To evaluate the proposal, we used three of the most relevant algorithms in the state-of-the art—SVM, Random Forest and Naive Bayes—and two corpora: the Reuters-21578 corpus and a purpose-built corpus, Reuters-27000. Results obtained show that the performance of the classification algorithm depends on the dataset used, and also demonstrate that the enrichment of the BoW representation with the concepts extracted from documents through the semantic annotator adds useful information to the classifier and improves their performance. Experiments conducted show performance increases up to 4.12% when classifying the Reuters-21578 corpus with the SVM algorithm and up to 49.35% when classifying the corpus Reuters-27000 with the Random Forest algorithm.

Introduction: Vitamin D3 activates via its hormonal form 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3), the transcription factor vitamin D receptor (VDR). VDR is expressed in most human tissues and has more than 1,000 target genes. Thus, 1α,25(OH)2D3 and its synthetic analogs have a broad physiological impact. The crystal structures of the VDR ligand-binding domain (LBD), and its various ligands, allows further the understanding of the receptor’s molecular actions.Areas covered: We discuss the most important novel VDR ligands and the further insight derived from new structural information on VDR.Expert opinion: There is an increasing appreciation of the impact of vitamin D and its receptor VDR not only in bone biology, but also for metabolic diseases, immunological disorders, and cancer. Detailed structural analysis of the interaction of additional novel ligands with VDR highlight helices 6 and 7 of the LBD as being most critical for stabilizing the receptor for an efficient interaction with co-activat...

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 synthesize a potent VDR agonist based on the skeleton of the hormone 1 a,25-dihydroxyvitamin D3(1,25D) and an o -carborane (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 hydroxyl interactions. 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 We thank the Spanish Ministry of Economy and Innovation (MEI, SAF2010-15291 and SAF2012-38240), Xunta de Galicia (project GPC2014/001), Agence Nationale de la Recherche (ANR- 13-BSV8-0024-01), French Infrastructure for Integrated Structural Biology (FRISBI) (ANR-10-INSB-05-01), and INSTRUCT as part of the European Strategy Forum on Research Infrastructures (ESFRI), for nancial support and CESGA for computing time. R. O. thanks the Spanish MEI for an FPI fellowship (BES-2011-0419192). S. S. thanks the Asociaci´on Espanola Contra el Cáncer for a fellowship (AIOA1101SEOA). R. S. thanks the Xunta de Galicia for a postdoctoral fellowship (POS-A/2012/112) SI

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 5a–c were efficiently synthesized from ketone 9 (which is readily accessible from the Inhoffen–Lythgoe diol) with overall yields of 15%, 6%, and 3% for 5a, 5b, and 5c, respectively. 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. © 2012 American Chemical Society., We thank the Spanish Ministry of Education and Innovation (SAF2007-67205 and SAF2010-15291 to A. Mouriño, SAF2010-18302 to A. Muñoz, and SAF2009-07631 to RPF) for financial support.

A convergent synthesis of an analogue of (1α)-1,25-dihydroxyvitamin D 3 (1b) with a C 7 side chain at C(12), i.e., of 5 (Fig.), is described. A key step of the synthesis is the assembly of the triene system by a Pd II-catalyzed ring closure of an enol triflate ('bottom' fragment) followed by coupling of the resulting Pd II intermediate with an alkenylboronate ('upper' fragment) (Scheme 2). The synthetic strategy allows isotopic labelling at the end of the synthesis. Copyright © 2012 Verlag Helvetica Chimica Acta AG, Zurich, Switzerland.

In the past years, the biologically active form of vitamin D(3), 1α,25-dihydroxyvitamin D(3) (1α,25(OH)(2)D(3)), has received large appreciation due to the broad physiological impact of the hormone and its nuclear receptor, the transcription factor vitamin D receptor (VDR). Recently, the understanding of VDR actions has progressed greatly, due to VDR crystal structures with various ligands.This review will present and discuss new synthetic agonistic and antagonistic 1α,25(OH)(2)D(3) analogs in the context of the recent insights provided by VDR crystal structures.During the last 5 years, a large number of new 1α,25(OH)(2)D(3) analogs, many of which have an interesting functional profile, have been patented. Moreover, for a surprisingly high number of 1α,25(OH)(2)D(3) analogs, the crystal structure data of their complex with the VDR is available. This structural information provides important insight into the functional potential of the VDR ligands and explains their agonistic and antagonistic action. However, so far, only for a few VDR ligands, a rational design, based on crystal structure information, has been applied. The design of future analogs may also take the specificity of co-factor interaction into account, in order to create selective VDR modulators.

El pdf es la versión de autor.-- et al., An improved synthetic route to 1α,25-dihydroxyvitamin D3 des-side chain analogues 2a and 2b with substituents at C18 is reported, along with their biological activity. These analogues display significant antiproliferative effects toward MCF-7 breast cancer cells and prodifferentiation activity toward SW480-ADH colon cancer cells; they are also characterized by a greatly decreased calcemic profile. The crystal structure of the human vitaminD receptor (hVDR) complexed to one of these analogues, 20(17→18)-abeo-1α,25-dihydroxy-22-homo-21-norvitamin D3 (2a) reveals that the side chain introduced at position C18 adopts the same orientation in the ligand binding pocket as the side chain of 1α,25-dihydroxyvitamin D3. Vitamin D3 supplements: The synthesis and biological activity of des-side chain analogues of 1α,25-dihydroxyvitamin D3 with substituents at C18 are described. Crystallographic analysis revealed that the new side chain introduced at C18 adopts the same orientation as the natural side chain at C17 in the parent molecule 1α,25-dihydroxyvitamin D3. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., This study was supported by the Spanish Ministry of Education and Science (Grants SAF2004-01885, SAF2007-60341, and SAF2007-67205), the European Union (MRTN-CT-2005-019496, NucSys), the Xunta de Galicia (Projets INCITE08PXIB-209130PR and ACEUIC-2006/XA050), Consolider, Nanobiomed, Fondo de Investigaciones Sanitarias, Fonds voor Wetenschappelijk Onderzoek (FWO) – Vlaanderen (G.553.06 and G.0587.09), CNRS, INSERM, Universit de Strasbourg, ANR, and the European Commission Structural Proteomics in Europe SPINE2-Complexes (LSHG-CT-2006-031220).

A review of the design and synthesis of structural analogs of the vitamin D hormone recently investigated in our laboratories, and the first report on a new class of vitamin D analogs characterized by an aromatic D-ring, is described. Fil: Eduardo, Silvina Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; Argentina. Universidad de Santiago de Compostela; España. Consejo Superior de Investigaciones Científicas; España Fil: Fraga, Ramón. Universidad de Santiago de Compostela; España. Consejo Superior de Investigaciones Científicas; España Fil: Sigüeiro, Rita. Universidad de Santiago de Compostela; España. Consejo Superior de Investigaciones Científicas; España Fil: Marco, Maria. Universidad de Santiago de Compostela; España. Consejo Superior de Investigaciones Científicas; España Fil: Rochel, Natacha. Universite Louis Pasteur; Francia Fil: Moras, Dino. Universite Louis Pasteur; Francia Fil: Mouriño, Antonio. Universidad de Santiago de Compostela; España. Consejo Superior de Investigaciones Científicas; España

Among more than 3000 analogs of 1α,25-dihydroxyvitamin D3 synthesized to date, only a few were characterized by structural modifications in the seco-B-ring. The compounds alkylated at C-6 seemed to be interesting targets for synthetic efforts. Such vitamin D analogs easily undergo thermal conversion to their previtamin forms. The results of molecular modeling indicate that significant deviation from planarity must be present in their molecules associated with the interaction of the 6-alkyl substituent and hydrogens from the C-ring. The synthesis of the analog of 1α,25-(OH)2D3, being characterized by the presence of the 6-methyl group, is reported here, together with the results of preliminary testing of its biological potency. This 6-alkylated compound was efficiently prepared using a novel stereoconvergent strategy in which the ring A and the triene unit of the vitamin D skeleton are constructed by a one-pot Pd-catalyzed tandem cyclization-Negishi coupling process. © 2010 Elsevier Ltd.

Chemical equation presented Daily vitamins: A mild, general, and highly stereoselective Pd0-catalyzed cascade to the triene system of the hoi mone 1α,25-dihydroxyvitamin D3 and six representative analogues is reported. The intramolecular cyclization of an enol-triflate (lower fragment) followed in situ by Suzuki Miyaura coupling with an alkenyl boronic ester (upper fragment, also efficiently prepared by Pd0-catalyzed coupling) in equimolar amounts under protic conditions is ideal for the preparation of small amounts of new vitamin D analogues for biological testing (see scheme). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA. Fil: Gogoi, Pranjal. Universidad de Santiago de Compostela; España. Consejo Superior de Investigaciones Científicas; España Fil: Sigüeiro, Rita. Consejo Superior de Investigaciones Científicas; España. Universidad de Santiago de Compostela; España Fil: Eduardo, Silvina Laura. Consejo Superior de Investigaciones Científicas; España. Universidad de Santiago de Compostela; España. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Mouriño, Antonio. Consejo Superior de Investigaciones Científicas; España. Universidad de Santiago de Compostela; España

The vitamin D nuclear receptor is a ligand-dependent transcription factor that controls multiple biological responses such as cell proliferation, immune responses, and bone mineralization. Numerous 1 alpha,25(OH)(2)D(3) analogues, which exhibit low calcemic side effects and/or antitumoral properties, have been synthesized. We recently showed that the synthetic analogue (20S,23S)-epoxymethano-1 alpha,25-dihydroxyvitamin D(3) (2a) acts as a 1 alpha,25(OH)(2)D(3) superagonist and exhibits both antiproliferative and prodifferentiating properties in vitro. Using this information and on the basis of the crystal structures of human VDR ligand binding domain (hVDR LBD) bound to 1 alpha,25(OH)(2)D(3), 2 alpha-methyl-1 alpha,25(OH)(2)D(3), or 2a, we designed a novel analogue, 2 alpha-methyl-(20S,23S)-epoxymethano-1 alpha,25-dihydroxyvitamin D(3) (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.

Vitamin D3 and its hydroxylated metabolites are normally in thermal equilibrium with their previtamin D isomers. To evaluate the biologic activity of 1 alpha, 25-dihydroxyprevitamin D3, we synthesized 19-nor analogs of 1 alpha, 25-dihydroxy(pre)vitamin D3 because the absence of a C19 methylene group prevents the isomerization of these analogs. The affinity of 1 alpha, 25-(OH)2D3-19-nor-D3 for the intestinal vitamin D receptor and plasma vitamin D binding protein was mildly decreased [30 and 20% of the affinity of 1 alpha, 25-(OH)2D3, respectively], but the affinity of 1 alpha, 25-(OH)2-19-nor-previtamin D3 was only 1 and 6% of that of 1 alpha, 25-(OH)2D3 for the receptor and DBP, respectively. The in vitro effects on human promyeloid leukemia (HL-60 cell) differentiation and osteocalcin secretion by human osteosarcoma (MG-63) cells by 1 alpha, 25-(OH)2-19-nor-D3 were nearly identical to those of 1 alpha-25-(OH)2D3, whereas 19-nor-previtamin D3 showed poor activity (2%). The in vivo calcemic effects of both analogs, studied in vitamin D-deficient chicks treated for 10 consecutive days with the analogs, showed no activity of the previtamin D3 analog and reduced calcemic effects (< or = 10%) of 1 alpha, 25-(OH)2-19-nor-D3. We conclude that the previtamin D form of 1 alpha, 25-(OH)2D3 has lost most of its biologic activity in vitro and in vivo.

SummaryVitamin D nuclear receptor (VDR), a ligand-dependent transcriptional regulator, is an important target for multiple clinical applications, such as osteoporosis and cancer. Since exacerbated increase of calcium serum level is currently associated with VDR ligands action, superagonists with low calcium serum levels have been developed. Based on the crystal structures of human VDR (hVDR) bound to 1α,25-dihydroxyvitamin D3 and superagonists—notably, KH1060—we designed a superagonist ligand. In order to optimize the aliphatic side chain conformation with a subsequent entropy benefit, we incorporated an oxolane ring and generated two stereo diasteromers, AMCR277A and AMCR277B. Only AMCR277A exhibits superagonist activity in vitro, but is as calcemic in vivo as the natural ligand. The crystal structures of the complexes between the ligand binding domain of hVDR and these ligands provide a rational approach to the design of more potent superagonist ligands for potential clinical application.

A mild and stereoconvergent synthesis of 1α25-dihydroxyvitamin D 3 (calcitriol, la) is described. The key step is a cascade process consisting of two consecutive transformations: An initial palladium-catalyzed 6-exo-cyclocarbopalladation of vinyl triflate 4 followed by a Negishi cross-coupling reaction with alkenyl zinc 3. This approach is of interest for the rapid synthesis of a variety of new vitamin D 3 analogues of therapeutic potential, especially those modified at the triene and ring-A. The mildness of the method also allows the preparation of thermal sensitive vitamin D 3 analogues.

The UV-induced photochemical reaction of 1α,25-dihydroxy-9-methylene-19-norvitamin D3 has been investigated. The pentacyclic structure of the isolated product has been unequivocally established by X-ray crystallographic analysis. The possible reaction paths of the examined photochemical transformation are discussed. Biological in vivo and in vitro tests proved that the photoproduct is devoid of calcemic activity.

Novel 19-norvitamin D analogues (ADYW1–4, 5a–d) in which an adamantyl diyne side chain is attached directly to the 17-position of the D ring are designed and stereoselectively synthesized. The adamantane ring of these analogues was expected to interfere with helix 12 (H12, activation function 2) of the vitamin D receptor (VDR) to modulate its activities. The analogue 5b binds to the VDR (7% of the natural hormone) and shows significant partial agonistic activity in transactivation assay. Compound 5b showed considerable selectivity in VDR target genes expressions in vitro, it was taken up by target cells 2–3 times more readily, and its lifetime was three times longer than the natural hormone. The X-ray crystal structure of 5b in complex with VDR reveals that the ligand binds similarly to the natural hormone, but the diyne moiety is slightly bent (angles around the diyne 5° to 8°) with respect to the original diyne vitamin D compound 6 in VDR (