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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 vitamin D hormone, 1,25dihydroxyvitamin D3 (1,25(OH)2D3), and related compounds derived from vitamin D3 or lumisterol as a result of metabolism via the enzyme CYP11A1, have been shown, when applied 24 hours before or immediately after UV irradiation, to protect human skin cells and skin from DNA damage due to UV exposure, by reducing both cyclobutane pyrimidine dimers (CPD) and oxidative damage in the form of 8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine (8‐OHdG). We now report that knockdown of either the vitamin D receptor or the endoplasmic reticulum protein ERp57 by small, interfering RNA (siRNA) abolished the reductions in UV‐induced DNA damage with 20‐hydroxyvitamin D3 or 24‐hydroxylumisterol3, as previously shown for 1,25(OH)2D3. Treatment with 1,25(OH)2D3 reduced oxygen consumption rates in UV‐exposed and sham‐exposed human keratinocytes and reduced phosphorylation of cyclic AMP response binding element protein (CREB). Both these actions have been shown to inhibit skin carcinogenesis after chronic UV exposure, consistent with the anticarcinogenic activity of 1,25(OH)2D3. The requirement for a vitamin D receptor for the photoprotective actions of 1,25(OH)2D3 and of naturally occurring CYP11A1‐derived vitamin D–related compounds may explain why mice lacking the vitamin D receptor in skin are more susceptible to UV‐induced skin cancers, whereas mice lacking the 1α‐hydroxylase and thus unable to make 1,25(OH)2D3 are not more susceptible. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

(23S,25R)-1α,25-Dihydroxyvitamin D3 26,23-lactone (calcitriol lactone) is a major metabolite of 1α,25-dihydroxyvitamin D3 that binds to vitamin D receptor (VDR) and exhibits various biological activities. This lactone and its derivatives are considered to have potential as drug candidates to treat VDR-related diseases, but their biological activities have not yet been fully characterized, mainly because of their limited availability by chemical synthesis. This review deals with synthetic studies of calcitriol lactone, and its derivatives, i.e., methylene lactones (TEI-9647 and its derivatives) and calcitriol lactams (DLAMs). We also discuss their biological activities, VDR-binding affinity and structure-activity relationships.

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 flexible approach to an A-ring building block for new 1α,25-dihydroxyvitamin D analogues functionalized at C-2 as potential clinical candidates is described. The synthesis of alcohol 5 starts from (R)-carvone, and uses a Criegee rearrangement to selectively degrade the isopropenyl side-chain as one of the key steps.

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.

The extracellular matrix protein nephronectin (Npnt), also called POEM, is considered to play critical roles as an adhesion molecule in development and functions of various tissues, such as the kidneys, liver, and bone. In the present study, we examined the molecular mechanism of Npnt gene expression and found that vitamin D3 (1α,25-dihydroxyvitamin D3,VD 3) strongly enhanced Npnt mRNA expression in MC3T3-E1 cells from a mouse osteoblastic cell line. The VD 3-induced increase in Npnt expression is both time- and dose-dependent and is mediated by the vitamin D receptor (VDR).

Calcitriol analogues which contained an oxime in the side chain were synthesised in five steps from an intermediate 22-nor Ketone. The key intermediate enones were synthesised by the Wittig–Horner olefination and Wittig olefination respectively. Reduction, oximation, photoisomerisation and deprotection gave the target compounds with the oxime at C-24.

It is well established that the mitochondria of proximal convoluted tubule cells of the kidney are the site of production of circulating 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3]. The production of 1,25(OH)2D3 at this site is tightly regulated. Parathyroid hormone markedly stimulates 1,25(OH)2D3 production, whereas 1,25(OH)2D3 itself suppresses production. The mechanism of suppression by 1,25(OH)2D3 has not yet been elucidated. We have now found that in the absence of vitamin D (vitamin D deficiency), the vitamin D receptor (VDR) is found in the interior of the apical brush border of the proximal tubule cells. This is unique for the proximal tubule cells, since this has not been observed in the distal tubule cells or in other epithelial cells, such as intestinal mucosa. Administration of 1,25(OH)2D3 to vitamin D-deficient rats results in the movement of VDR from the brush border to the cytoplasm and nucleus presumably bound to reabsorbed 1,25(OH)2D3. The VDR bound to 1,25(OH)2D3 suppresses expression of 25-hydroxyvitamin D3 1α-hydroxylase and stimulates the 25-hydroxyvitamin D3 24-hydroxylase. Thus, VDR in the apical brush border of the proximal convoluted tubule cells serves to “sense” the level of circulating 1,25(OH)2D3 and modulates the activity of the 1α-hydroxylase and the 24-hydroxylase accordingly.

The aim of this study was to assess the impact of 1α,25-dihydroxyvitamin D3 (vitamin D3) on osteogenic and inflammatory properties of human periodontal ligament (PDL) cells and investigate underlying mechanisms.Human PDL cells, obtained from four subjects, were stimulated with vitamin D3 for 4-48 h. The bone markers osteopontin and osteocalcin and proinflammatory cytokine/chemokine expression was determined by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay. Cytokine and chemokine expression was determined after stimulation with the inflammation promoter lipopolysaccharide (LPS) in the presence or absence of vitamin D3. Alkaline phosphatase activity was assessed using p-nitrophenylphosphate substrate.Treatment with 30 ng/mL of vitamin D3, corresponding to an optimal plasma concentration of vitamin D, for 24 h had no effect on PDL cell number and morphology but increased PDL cell osteopontin and osteocalcin mRNA expression by about 70 and 40%, respectively, and, moreover, treatment with vitamin D3 for 48 h enhanced PDL cell alkaline phosphatase activity by about two times showing that vitamin D3 exerts pro-osteogenic effects in human PDL cells. Stimulation with LPS (1 μg/mL) for 4 h increased PDL cell interleukin (IL)-6 cytokine and chemokine ligand 1 (CXCL1) chemokine mRNA expression several fold. The LPS-induced increase in IL-6 and CXCL1 transcripts was attenuated by vitamin D3 (30 ng/mL). Treatment with vitamin D3 (3-300 ng/mL) for 24 h reduced the LPS-evoked increase in PDL cell IL-6 protein by about 50%. Vitamin D3 (30 ng/mL) had no effect on LPS-induced IL-1β and MCP-1 mRNA expression.Vitamin D3 promotes osteogenic differentiation but also downregulates inflammation promoter-induced IL-6 cytokine and CXCL1 chemokine expression in human PDL cells, suggesting that vitamin D3 both stimulates bone regeneration and antagonizes inflammation in human periodontal tissue.

The synthesis of two new A-ring precursors, useful for the convergent assembly of 2α-ethyl and 2β-ethyl derivatives of 19-nor-1α,25-dihydroxyvitamin D3, is described. These building blocks were prepared in 14 steps from quinic acid, which led to a new and practical synthesis of 2α-ethyl-14-epi-19-nor-20-epi-23-yne-1,25(OH)2D3, an analog that shows a remarkably low calcemic effect in mice, while retaining the ability to promote cell differentiation and to inhibit cell proliferation in a number of human cancer cell lines.

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.

This review highlights the superseding role of mass spectrometry in the structural characterization and quantitation of vitamin D compounds in comparison to other analytical methods (e.g., UV, bioassays) that lack the sensitivity and specificity of mass spectrometry. After a short introduction to the biochemistry of vitamin D compounds, an overview of the current techniques to characterize and quantitate vitamin D compounds is given with emphasis on the contribution of mass spectrometry.

Access to the calcitriol analogues with a tetrazole ring at the side chain was very efficiently achieved using the Calverley-Choudhry approach instead of the Wittig-Horner method, which gave very low yields.

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 novel approach to the key A-ring α, β-unsaturated aldehyde 1, an important intermediate for the preparation of 1α,25-dihydroxyvitamin D(3), has been developed. The strategy started from the inexpensive starting material (R)-carvone with an ene reaction serving as the key step toward the potential synthesis of vitamin D(3) analogues bearing the modification at the C-2 position.

1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3] directly induces both fusion and cytotoxicity in murine alveolar macrophages. Unlike 1 alpha,25(OH)2D3, retinoic acid per se did not induce fusion of alveolar macrophages, but it greatly enhanced the 1 alpha,25(OH)2D3-induced fusion every time the macrophages were treated simultaneously with the two vitamins. The giant cells induced by the two vitamins were much larger than those induced by 1 alpha,25(OH)2D3 alone. The macrophages treated with 1 alpha,25(OH)2D3 started to fuse 36 h after the addition of the vitamin, whereas the macrophages pretreated with retinoic acid for 24 h began to fuse immediately after 1 alpha,25(OH)2D3 was added. 1 alpha,25(OH)2D3 and retinoic acid activated alveolar macrophages similarly, measured by the enhancement of glucose consumption and the induction of cytotoxicity against tumor cells, though 1 alpha,25(OH)2D3 was 100 times more potent than retinoic acid on a molar basis. Simultaneous treatment with physiological concentrations of 1 alpha,25(OH)2D3 (0.12 nM) and retinoic acid (10 nM) induced cytotoxicity additively. Morphological examinations revealed that the treated cells were enlarged and flattened with numerous filopodia. These results clearly indicate that both 1 alpha,25(OH)2D3 and retinoic acid similarly activate alveolar macrophages, and the activated state is prerequisite to the fusion of macrophages induced by 1 alpha,25(OH)2D3.

In search of analogs of 1α,25-dihydroxyvitamin D3 featuring a dissociation of calcemic and other activities, a series of stereoisomeric 19-nor-22-oxa derivatives, characterized by a spiro[4.5]decane cyclic system instead of the classical CD-ring system, have been synthesized in an enantioselective way.

The discovery that 1 alpha,25-dihydroxyvitamin D-3 is effective in the inhibition of cellular proliferation and in the induction of cellular differentiation has led to a search for analogues in which these activities and the classical calcemic activity of the hormone are dissociated. In this context, the synthesis and biological evaluation are reported for six CD-ring modified structural analogues that were conceived so as to enforce a particular orientation of the 25-hydroxylated side chain. The analogues are characterized by the absence of the C-ring and the presence of an unnatural six-membered D-ring. The biased side-chain orientations are realized through the stereocontrolled incorporation of methyl substituents at positions C13/C20 and C16/C20. Comparison of the results of the biological evaluation and conformational analysis of the side chain confirms the existence of a relationship between inhibition of MCF-7 breast cancer cell proliferation and side chain geometry. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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.

Replacing the 1alpha-OH group of the natural hormone 1alpha,25-dihydroxyvitamin D(3) (calcitriol) by a 1alpha-CHF(2) group and incorporating a potentiating side chain produced two new hybrid analogs 6 and 7. Both of these two hybrid analogs are as transcriptionally active as calcitriol and are strongly antiproliferative in vitro but are low-calcemic in vivo.

The synthesis of several 19-nor-2-alkyl-1α,25-dihydroxyvitamin D3 analogues (5–14) is described following the cyclovitamin strategy. Starting from all-cis methyl 3,5-dihydroxy-4-alkyl-1-cyclohexanecarboxylate (29), the eight stereoisomeric A-ring-precursor 2-tert-butyldiphenylsilyloxy-3α-formyl-1-alkylbicyclo[3.1.0]hexanes (39, 44, 46, 63, 65, 67, 69, 71) were prepared in two series: a (R = methyl) and b (R = ethyl). In particular, from the coupling of 39 and the lithiated compounds derived from the CD-ring bromides 20 and 21 possessing the natural or the 23-yne side chain, the title derivatives 5–14 were synthesized. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

We synthesized all eight possible A-ring diastereomers of 2-methyl substituted analogs of 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] and also all eight A-ring diastereomers of 2-methyl-20-epi-1alpha,25(OH)2D3. Their biological activities, especially the antagonistic effect on non-genomic pathway-mediated responses induced by 1alpha,25(OH)2D3 or its 6-s-cis-conformer analog, 1alpha,25(OH)2-lumisterol3, were assessed using an NB4 cell differentiation system. Antagonistic activity was observed for the 1beta-hydroxyl diastereomers, including 2beta-methyl-1beta,25(OH)2D3 and 2beta-methyl-3-epi-1beta,25(OH)2D3. Very interestingly, 2beta-methyl-3-epi-1alpha,25(OH)2D3 also antagonized the non-genomic pathway, despite its 1alpha-hydroxyl group. Other 1alpha-hydroxyl diastereomers did not show antagonistic activity. 20-epimerization diminished the antagonistic effect of all of these analogs on the non-genomic pathway. These findings suggested that the combination of the 2-methyl substitution of the A-ring and 20-epimerization of the side chain could alter the biological activities in terms of antagonism of non-genomic pathway-mediated biological response. Based on a previous report, 2-methyl substitution alters the equilibrium of the A-ring conformation between the alpha- and beta-chair conformers. The 2beta-methyl diastereomers, which exhibited antagonism on non-genomic pathway-mediated response, were considered to prefer the beta-conformer. Further examination to elucidate the relationship between the altered ligand shape and receptors interaction will be important for molecular level understanding of the mechanism of antagonism of the non-genomic pathway.

Two 21-nor-22-oxa-1α,25-dihydroxyvitamin D 3 derivatives have been synthesized in quest of a drug with lower calcemic activity than Maxacalcitol, 22-oxa-1α,25-dihydroxyvitamin D 3 , being used as antihyperparathyroidism and antipsoriatic drug. Of two 21-nor products obtained, the product carrying one carbon elongated side chain with diethylcarbinol moiety has been found to exhibit comparable differentiation-inducing activity to Maxacalcitol with much lower exhibition of calcemic activity.

Based on an X-ray crystal structure determination, the A-ring stereochemistry of hybrid analog QW-1624F2-2 (1alpha-hydroxymethyl-16-ene-24,24-difluoro-25-hydroxy-26,27-bis-homovitamin D3) is revised to be 1alpha-CH2OH-3beta-OH. This analog is shown to be approximately 80-100 times less calciuric than the natural hormone 1alpha,25-dihydoxyvitamin D3. This analog is shown also to be non-genotoxic in three different standard assays.

A concise and efficient synthetic approach to 2 alpha-(omega-hydroxyalkoxy)-1 alpha,25-dihydroxyvitamin D(3) (4a-c), including 2-epi-ED-71, was developed starting from D-glucose as a chiral template for the construction of the 2 alpha-modified A-ring precursors (11a-c). It was found that the best ligand for the bovine thymus vitamin D receptor (VDR) in this series is 4b, which has 1.8 times greater binding affinity for the bovine thymus VDR than that of the natural hormone 1. Interestingly, potency in the induction of HL-60 cell differentiation for 4a-c was almost the same or weaker than that of 1 despite the strong binding affinity for the VDR. Next, we were interested in the "double modification"of 1 based on 4a-c with C20-epimerization, affording 2 alpha-(omega-hydroxyalkoxy)-20-epi-1 alpha,25-dihydroxyvitamin D(3) (20-epi-4a-c). All three 2 alpha-substituted 20-epi analogues of 1 (20-epi-4a-c) exhibited stronger binding affinities for the VDR, and their conformations in the ligand binding domain of VDR were analyzed by molecular modeling. Double-modified analogues of 20-epi-4a-c showed marked HL-60 cell differentiation activity, and 20-epi-4a possesses an activity 58-fold higher than that of the natural hormone 1.

The metabolism of 1alpha,25(OH)(2)D(3) (1alpha,3beta) and its A-ring diastereomers, 1beta,25(OH)(2)D(3) (1beta,3beta), 1alpha,25(OH)(2)-3-epi-D(3) (1alpha,3alpha), and 1beta,25(OH)(2)-3-epi-D(3) (1beta,3alpha), was examined to compare the substrate specificity and reaction specificity of CYP24A1 between humans and rats. The ratio between C-23 and C-24 oxidation pathways in human CYP24A1-dependent metabolism of (1alpha,3alpha) and (1beta,3alpha) was 1:1, although the ratio for (1alpha,3beta) and (1beta,3beta) was 1:4. These results indicate that the orientation of the hydroxyl group at the C-3 position determines the ratio between C-23 and C-24 oxidation pathways. A remarkable increase of metabolites in the C-23 oxidation pathway was also observed in rat CYP24A1-dependent metabolism. The binding affinity of human CYP24A1 for A-ring diastereomers was (1alpha,3beta)(1alpha,3alpha)(1beta,3beta)(1beta,3alpha), indicating that both hydroxyl groups at C-1 and C-3 positions significantly affect substrate-binding. The information obtained in this study is quite useful for understanding substrate recognition of CYP24A1 and designing new vitamin D analogs.

Novel analogues of the hormone 1alpha,25-(OH)(2)-D(3) with side chains attached to C-18 were synthesized by a versatile route in which key steps were the remote radical-induced functionalization of the 18-methyl by the C-8beta-hydroxyl group and the introduction of the side chains by Wittig reactions on a C-18-aldehyde. The triene system of the novel analogues was constructed by the convergent Lythgoe-Hoffmann la Roche approach, which involves reaction of a phosphine oxide (the ring A fragment) with a ketone (the upper fragment).

Novel vitamin D(3) analogs having a lactam structure in their side chains, 1 alpha,25-dihydroxyvitamin D(3)-26,23-lactams (DLAMs), were designed based on the principle of regulation of the folding of helix-12 in the vitamin D nuclear receptor (VDR). The new analogs were synthesized via 1,3-dipolar cycloaddition reaction and subsequent reduction of the isoxazolidine as key steps. Among the analogs, (23S,25S)-DLAM-01 (4a) and (23S,25S)-DLAM-1P (5a) bind strongly to VDR. Moreover, these analogs were found to inhibit the differentiation of HL-60 cells induced by 1 alpha,25-dihydroxyvitamin D(3).

Vitamin D3 and its synthetic analogs are promising compounds for controlling various types of cell differentiation. In this article, we describe the synthesis of novel vitamin D3 analogs containing heteroatoms in their side chains – so-called vitamin D3 lactam analogs – via 1,3-dipolar cycloaddition reaction as a key step.

We present our first results on the synthesis of a new class of conformationally restricted vitamin D analogues bearing an extra five-membered ring formed by linking C(18) and C(21). Two analogues of calcitriol (1) with unsaturations at the extra ring and the lateral chain were prepared. The triene system was introduced by the convergent Wittig-Horner approach developed by Lythgoe [8] and F Hoffmann-La Roche [9]. The key steps in the preparation of the requisite fragments were: i) the long-distance functionalization of ketal 11 at C(18), ii) the ring closure on 15 through an intramolecular aldol condensation to give the α,β-unsaturated ketone 10, and iii) the Pd-catalyzed installation of the side chains.

The synthesis and biological activities of seco C-9,11,21-trisnor-17-methyl-1 alpha,25-dihydroxyvitamin D(3) analogues (D-ring analogues) are described.

1α,25-Dihydroxyvitamin D3, the hormonal form of vitamin D3, is widely appreciated to play a central role in calcium and phosphorous homeostasis. It is becoming increasingly clear, however, that the sterol also plays an important role in the regulation of cellular growth, central nervous system function, and immune responsiveness. In this review, I will highlight some of the mechanisms by which 1α,25-dihydroxyvitamin D3 regulates cellular growth, alters central nervous system function, and immune function.

In the present study, the chemopreventive effect of the active metabolite of vitamin D, 1α,25-dihydroxyvitamin D3 (VD3), against chemically-induced and diabetes-promoted rat liver carcinogenesis was investigated. Hepatocarcinogenesis was initiated with a single intraperitoneal (i.p.) injection of diethylnitrosamine (DEN) (125 mg kg−1 body weight) at week 4 followed by promotion with streptozotocin (STZ) (65 mg kg−1 body weight with a single i.p. injection) at week 7. With this basic experimental regimen, the effect of VD3 (0.3 μg (0.1 ml)−1 propylene glycol per os twice a week) was investigated with effect from 4 weeks prior to the exposure of DEN. The results showed that VD3 supplementation throughout the experimental period reduced the incidence, total number and multiplicity and altered the size of visible persistent nodules (PNs) in DEN- or DEN + STZ-treated rats as compared with their respective controls. In these two groups, it also caused a significant decrease in the number (p

Vitamin D receptor (VDR) regulates the expression of a broad array of genes, including those involved in drug biotransformation (e.g. CYP2B6). Ginkgo biloba extract induces CYP2B6, but it is not kn...

We reported recently that suppression of the renal 1alpha,25-dihyroxyvitamin D3 (1lpha,25-(OH)2-D3) production in aP2-agouti transgenic mice by increasing dietary calcium decreases adipocyte intracellular Ca2+ ([Ca2+]i), stimulates lipolysis, inhibits lipogenesis, and reduces adiposity. However, it was not clear whether this modulation of adipocyte metabolism by dietary calcium is a direct effect of inhibition of 1alpha,25-(OH)2-D3-induced [Ca2+]i. Accordingly, we have now evaluated the direct role of 1alpha,25-(OH)2-D3. Human adipocytes exhibited a 1alpha,25-(OH)2-D3 dose-responsive (1-50 nM) increase in [Ca2+]i (P0.01). This action was mimicked by 1alpha,25-dihyroxylumisterol3 (1alpha,25-(OH)2-lumisterol3) (P0.001), a specific agonist for a putative membrane vitamin D receptor (mVDR), and completely prevented by 1b,25-dihydroxyvitamin D3 (1beta,25-(OH)2-D3), a specific antagonist for the mVDR. Similarly, 1alpha,25-(OH)2-D3 (5 nM) caused 50%-100% increases in adipocyte fatty acid synthase (FAS) expression and activity (P0.02), a 61% increase in glycerol-3-phosphate dehydrogenase (GPDH) activity (P0.01), and an 80% inhibition of isoproterenol-stimulated lipolysis (P0.001), whereas 1beta,25-(OH)2-D3 completely blocked all these effects. Notably, 1alpha,25-(OH)2-lumisterol3 exerted more potent effects in modulating adipocyte lipid metabolism, with 2.5- to 3.0-fold increases in FAS expression and activity (P0.001) and a threefold increase in GPDH activity (P0.001). Also 1alpha,25-(OH)2-lumisterol3 was approximately twice as potent in inhibiting basal lipolysis (P0.025), whereas 1beta,25-(OH)2-D3 completely blocked all these effects. These data suggest that 1alpha,25-(OH)2-D3 modulates adipocyte Ca2+ signaling and, consequently, exerts a coordinated control over lipogenesis and lipolysis. Thus, a direct inhibition of 1alpha,25-(OH)2-D3-induced [Ca2+]i may contribute to an anti-obesity effect of dietary calcium, and the mVDR may represent an important target for obesity.

A practical synthesis of (2S,3aS,4aS)-2-tert-butyldimethylsilyloxybicyclo[3.1.0]hexane-3a-carbaldehyde (14a) and diastereoisomers, starting from all-cis methyl 3,5-dihydroxy-1cyclohexanecarboxylate (24) is described. Coupling with appropriate cis-hydrindanes produces the title compounds. TX 522, a member of this series, is currently in phase II clinical studies for the treatment of psoriasis. The key step involves the coupling of 14 and 16 with the respective cis-hydrindanes 9 and 7.

The discovery that 1α,25-dihydroxyvitamin D3 is effective in the inhibition of cellular proliferation and in the induction of cellular differentiation has led to a search for analogues in which these activities and the classical calcemic activity of this hormone are separated. In this context, the synthesis and biological evaluation are reported of the three stereoisomeric CD-ring modified structural analogues in order to enforce a particular and different orientation of the 25-hydroxylated side chain. Comparison of the results of the biological evaluation and conformational analysis of the side chain suggests one defined and “active” geometry.

The synthesis of four new analogues of calcitriol (1α,25-(OH)2-D3)possessing aromatic and conjugated double bond units at the side chain are described. The triene system is introduced using the Lythgoe−Hoffmann La Roche convergent Wittig−Horner approach. The key steps in the preparation of the requisite upper fragments are the introduction of the side chain with the E-conjugated aromatic system and its photochemical conversion to the Z counterpart.

A simple and direct approach to both enantiomeric series of A-ring derivatives of 1α,25-dihydroxyvitamin D 3 and the corresponding 1α,3α-derivatives, starting from the abundantly available R -carvone, is described.

An efficient synthesis of A-ring precursors 8 and 9 from inexpensive commercially available (−)-quinic acid has been developed. A-Ring synthon 8 has been obtained through a short sequence (eight steps) in high overall yield (30%). One key step in the synthesis of A-ring precursor 9 is the selective deprotection of a silyl ether in an α,β-unsaturated ester 12. However, of note is the excellent yield of the Mitsunobu process on derivative 15, which takes place with the total inversion of configuration, giving ester 16. Coupling of A-ring synthons 8 and 9 with the appropriate CD-rings/side chain fragment 7, provides access to 6-s-cis locked analogues of the steroid hormone 1α,25-(OH)2-D3: 1α,25-(OH)2-19-nor-pre-D3 (3) and novel 1β,25-(OH)2-19-nor-pre-D3 (4).

We recently identified 1alpha,25-dihydroxy-3-epi-vitamin D3 as a major in vitro metabolite of 1alpha,25-dihydroxyvitamin D3, produced in primary cultures of neonatal human keratinocytes. We now report the isolation of 1alpha,25-dihydroxy-3-epi-vitamin D3 from the serum of rats treated with pharmacological doses of 1alpha,25-dihydroxyvitamin D3. 1alpha,25-dihydroxy-3-epi-vitamin D3 was identified through its co-migration with synthetic 1alpha,25-dihydroxy-3-epi-vitamin D3 on both straight and reverse phase high performance liquid chromatography systems and by mass spectrometry. Along with 1alpha,25-dihydroxy-3-epi-vitamin D3, other previously known metabolites, namely, 1alpha,24(R),25-trihydroxyvitamin D3, 1alpha,25-dihydroxy-24-oxo-vitamin D3 and 1alpha,25-dihydroxyvitamin D3-26,23-lactone, were also identified. Thus, our study for the first time provides direct evidence to indicate that 1alpha,25-dihydroxy-3-epi-vitamin D3 is an in vivo metabolite of 1alpha,25-dihydroxyvitamin D3 in rats.

4,4-Difluoro-1α,25-dihydroxyvitamin D 3 was synthesized from ergosterol and analysis of its 19 F NMR showed it to be a useful probe to analyze the receptor-bound A-ring conformation of vitamin D.

(25S)-24,24-Difluoro-1α,25,26-trihydroxyvitamin D3 (3a and its (25R)-epimer (3b), either of which is expected to be a major metabolite of 24,24-difluoro-1α,25-dihydroxyvitamin D3 (2), were synthesized. Asymmetric addition to β-ketosulfoxides (5a, 5b) of trimethylaluminum was used as a key process to construct the chiral tertiary alcohol moiety of 3a and 3b. The absolute configuration of the tertiary alcohol was determined by X-ray crystallographic analysis of 20 which is a CD-ring analog of the 3a intermediate. The configuration at the C(25) position of the metabolite was established as S by HPLC comparison between the metabolite and chemically synthesized 3a and 3b.

It is an important question for clinical therapy of osteoporosis with vitamin D metabolites whether these compounds exert their beneficial effects on the skeleton indirectly through an increase in intestinal calcium absorption or whether there is also a major direct component of action on bone. In this study, female 6-month-old Fischer rats were either ovariectomized (OVX) or sham operated. One month before surgery, all rats were placed on a diet containing 0.25% calcium and were kept on this diet throughout the study. Beginning 3 months post-OVX, groups of OVX rats orally received vehicle, a calcium supplement, low dose (0.025 μg/kg·day) or high dose (0.1 μg/kg·day) 1α,25-dihydroxyvitamin D3[ 1,25-(OH)2D3], or combinations of low and high dose 1,25-(OH)2D3 with the calcium supplement. By 3 months postsurgery, pretreatment OVX controls had lost 74% and 37% of tibial and vertebral cancellous bone, respectively. Two-way factorial ANOVA showed that a 3-month treatment of osteopenic OVX rats with 1,25-(OH)2D3...

A series of semi-rigid analogues of the hormone 1α,25-dihydroxyvitamin D3 have been designed in order to study the topology required for binding to the hormone receptor (VDR). The new vitamin D3 analogues 2-5 possess a rigid C17-C20 bond and minimal structural modifications on the side-chain with respect to the hormone. Key steps for the introduction of the side-chains of the new analogues 2-5 from hydrindanone 6 involve a stereoselective Wittig reaction, olefin isomerization and dihalocyclopropanation.

This paper have delineated the effectiveness of [3+2] cycloaddition process in the synthesis of multifunctional 6-membered rings. The novel synthesis of chiral A-ring fragment of 1α,25-dihydroxyvitamin D 3 and also a novel route to A-ring fragment of taxane diterpenoids have been established.