Synthesis of 25-Hydroxy-provitamin D3 by Direct Hydroxylation of Protected 7-Dehydrocholesterol.

A new synthetic route to 25-hydroxy-provitamin D3 was elaborated. The synthesis consists of direct hydroxylation at C-25 of 7-dehydrocholesterol hetero Diels-Alder adducts. The adducts were prepared by [4 + 2] cycloaddition of azadienophiles to the steroidal diene. The hydroxylation reactions of adducts were carried out with different dioxiranes or with chromyl trifluoroacetate. The byproducts of these reactions were isolated and identified. The strengths and weaknesses of hydroxylation methods with different oxidizing agents were discussed.

Montmorillonite Catalyzed Synthesis of Novel Steroid Dimers.

The reactions of sterols (androst-5-en-3ß-ol-17-one, diosgenin, and cholesterol) and their tosylates with hydroquinone aimed at the synthesis of O,O-1,4-phenylene-linked steroid dimers were studied. The reaction course strongly depended on the conditions used. The study has shown that the major reaction products are the elimination products and unusual steroid dimers resulting from the nucleophilic attack of the hydroquinone C2 carbon atom on the steroid C3 position, followed by an intramolecular addition to the C5-C6 double bond. A different reaction course was observed when montmorillonite K10 was used as a catalyst. The reaction of androst-5-en-3ß-ol-17-one under the promotion of this catalyst afforded the O,O-1,4-phenylene-linked steroid dimer in addition to the disteroidal ether. The formation of the latter compound was suppressed by using 3-tosylate as a substrate instead of the free sterol. The reactions of androst-5-en-3ß-ol-17-one tosylate and cholesteryl tosylate with hydroquinone catalyzed by montmorillonite K10 carried out under optimized conditions afforded the desired dimers in 31% and 67% yield, respectively.

A Simple Four-Step Synthesis of the Potato Alkaloid Demissidine from the Common Sapogenin Tigogenin.

A simple synthesis method of solanidane alkaloids from common steroidal sapogenins was developed. Previously described multi-step transformations of tigogenin to demissidine (8-12 steps) were shortened to four steps only. The key-step of the present synthesis was the epimerization at C25 of the lactam intermediate. Different approaches to this reaction, i. e., a classical one via enolate, and a chemoselective umpolung transformation, were thoroughly investigated. The epimerization step is unnecessary if the starting sapogenin has the same configuration at C25 as the target alkaloid because the configuration at C25 (either R or S) remains intact throughout the synthesis. Thus, the related solanidane alkaloids, 12ß-hydroxy-25-epi-demissidine and 5-epi-demissidine, were synthesized in the three-step procedure with retention of configuration at this stereogenic center from rockogenin (25R-5α-sapogenin) or sarsasapogenin (25S-5ß-sapogenin), respectively.

Concise synthesis of E/F ring spiroethers from tigogenin. Carbaanalogs of steroidal sapogenins and their biological activity.

A four-step synthesis of five- and six-membered E/F ring spiroethers from tigogenin has been developed. An efficient strategy that features bis-Grignard reaction of dinorcholanic lactone with appropriate bis(bromomagnesio)alkanes followed by acid-mediated spirocyclization was employed to construct a new class of steroid compounds having E and F ring junction as an oxa-carbacyclic system. The synthesized carbaanalogs interact with liposomes and albumin, and also exhibit antibacterial and antifungal activity, demonstrating their pharmacological potential.

Establishment of In Vitro and In Vivo Anticolorectal Cancer Efficacy of Lithocholic Acid-Based Imidazolium Salts.

Imidazolium salts (IMSs) are the subject of many studies showing their anticancer activities. In this research, a series of novel imidazolium salts substituted with lithocholic acid (LCA) and alkyl chains of various lengths (S1-S10) were evaluated against colon cancer cells. A significant reduction in the viability and metabolic activity was obtained in vitro for DLD-1 and HT-29 cell lines when treated with tested salts. The results showed that the activities of tested agents are directly related to the alkyl chain length, where S6-S8 compounds were the most cytotoxic against the DLD-1 line and S4-S10 against HT-29. The research performed on the xenograft model of mice demonstrated a lower tendency of tumor growth in the group receiving compound S6, compared with the group receiving 5-fluorouracil (5-FU). Obtained results indicate the activity of S6 in the induction of apoptosis and necrosis in induced colorectal cancer. LCA-based imidazolium salts may be candidates for chemotherapeutic agents against colorectal cancer.

A Study on the Chemistry and Biological Activity of 26-Sulfur Analogs of Diosgenin: Synthesis of 26-Thiodiosgenin S-Mono- and Dioxides, and Their Alkyl Derivatives.

A chemoselective procedure for MCPBA oxidation of 26-thiodiosgenin to corresponding sulfoxides and sulfone was elaborated. An unusual equilibration of sulfoxides in solution was observed. Moreover, α-alkylation of sulfoxide and sulfone was investigated. Finally, the biological activity of obtained compounds was examined.

Synthesis of Demissidine Analogues from Tigogenin via Imine Intermediates.

A five-step transformation of a spiroketal side chain of tigogenin into an indolizidine system present in solanidane alkaloids such as demissidine and solanidine was elaborated. The key intermediate in the synthesis was spiroimine 3 readily obtained from tigogenin by its RuO4 oxidation to 5,6-dihydrokryptogenin followed by amination with aluminum amide generated in situ from DIBAlH and ammonium chloride. The mild reduction of spiroimine to a 26-hydroxy-dihydropyrrole derivative and subsequent mesylation resulted in the formation of 25-epidemissidinium salt or 23-sulfone depending on reaction conditions.

Synthesis of Solanum Alkaloid Demissidine Stereoisomers and Analogues.

Demissidine is an indolizidine alkaloid isolated from several potato species. A simple synthesis of demissidine stereoisomers and analogues from a common steroidal sapogenin tigogenin is presented in the paper. The key intermediate in the synthesis of these compounds is readily available tigogenoic acid. Its step-by-step transformation to indolizidine yielded 20R,25R or 20R,25S products while the direct reductive amination produced the 20S,25R compound (25-epi-demissidine).

Dehydroepiandrosterone derived imidazolium salts and their antimicrobial efficacy.

Hybrid molecules consisting of steroid-imidazolium salts reveal interesting biological properties, especially regarding antimicrobial activities. Novel dehydroepiandrosterone derived imidazolium salts (11 salts) with side chains of different lengths were obtained in an efficient and straightforward synthetic route. Antimicrobial properties of new salts were examined by determining their minimum inhibitory concentrations (MICs). They were studied against several strains of bacteria, including clinical isolates of MRSA, and fungi. New compounds showed high activity against Gram-positive bacteria and Candida albicans as well as good compatibility with the representatives of the host cells when applied at concentrations corresponding to MIC value. The studies indicated high antimicrobial efficacy of imidazolium salts against the above-mentioned microorganisms with low hemolytic activity at a concentration that restricts the growth of the microorganisms. The interference of salts with the immune defense system, the influence on the biological activity of monocytes/macrophages measured by their viability and metabolic activity was also studied. The new compounds have shown immunoprotective properties.

The synthesis and cholinesterase inhibitory activities of solasodine analogues with seven-membered F ring.

Solasodine analogues containing a seven-membered F ring with a nitrogen atom placed at position 22a were prepared from diosgenin or tigogenin in a four-step synthesis comprising of the simultaneous opening of the F-ring and introduction of cyanide in position 22α, activation of the 26-hydroxyl group as mesylate, nitrile reduction, and N-cyclization. Solasodine, six obtained 22a(N)-homo analogues, as well as four 26a-homosolasodine derivatives and their open-chain precursors (13 in total) were tested as potential inhibitors of acetyl- and butyryl-cholinesterases and showed activity at micromolar concentrations. The structure-activity relationship study revealed that activities against studied esterases are affected by the structure of E/F rings and the substitution pattern of ring A. The most potent compound 8 acted as non-competitive inhibitors and exerted IC50 = 8.51 µM and 7.05 µM for eeAChE and eqBChE, respectively. Molecular docking studies revealed the hydrogen bond interaction of 8 with S293 of AChE; further rings are stabilized via hydrophobic interaction (ring A) or interaction with Y341 and W286 (rings B and C). Biological experiments showed no neurotoxicity of differentiated SH-SY5Y cells. More importantly, results from neuroprotective assay based on glutamate-induced cytotoxicity revealed that most derivatives had the ability to increase the viability of differentiated SH-SY5Y cells in comparison to galantamine and lipoic acid assayed as standards. The newly synthesized solasodine analogues are able to inhibit and to bind cholinesterases in noncompetitive mode of inhibition and exhibited neuroprotection potential of differentiated neuroblastoma cells after Glu-induced toxicity.

A Convenient Synthesis of (16S,20S)-3ß-hydroxy-5α-pregnane-20,16-carbolactam and its N-alkyl Derivatives.

A concise synthesis of (16S,20S)-3ß-hydroxy-5α-pregnane-20,16-carbolactam from tigogenin via the corresponding lactone is described. The most efficient synthetic route consisted of the lactone ring-opening with aminoalane reagent followed by PDC or Dess-Martin oxidation. The oxo-amide obtained was subjected to cyclization with Et3SiH/TFA or Et3SiH/Bi(TfO)3. Alternately, the lactone was converted first to the oxo-acid, which was then subjected to the microwave-assisted reductive amination. N-Alkyl derivatives were also obtained in a similar way.

The synthesis of solasodine F-homo-analogues.

Solasodine derivatives continue to be attractive targets for synthetic chemists due to their interesting biological properties. Herein, we report a concise synthesis of solasodine analogues containing the seven-membered F ring from diosgenin. The key intermediate in the synthesis of 26a-homosolane derivatives was 26-cyanopseudodiosgenin. After reduction of the cyano group, the seven-membered ring was closed with MgBr2·Et2O to yield 26a-homosolanes as a mixture of 22R and 22S epimers. The acylation of the obtained mixture led to the diastereomerically pure 22S N-acylated 26a-homosolasodine derivatives. Moreover, we describe one-step protocol for stereoselective synthesis of 22R-cyanofurostane by treatment of diosgenin with TMSCN/BF3·Et2O.

TiCl4 catalyzed cleavage of (25R)-22-oxo-23-spiroketals. Synthesis of sapogenins with furostanol and pyranone E rings on the side chain.

The regioselective opening of the F ring of 22-oxo-23-spiroketals 7a-d using TiCl4 in acetic anhydride yielded the novel furostanols 11a-d along with cholestanic derivatives 8a-d with pyranone E ring. The structures of the new derivatives thus obtained were established using one- (DEPT) and two-dimensional 1H, 13C NMR experiments (COSY, HSQC, HMBC, NOESY). The 22α-hydroxyl orientation in compounds 11a-d was proposed by comparison of the 13C chemical shifts with those of other aglycone members of this family, and confirmed by combined NOESY and X-ray diffraction analysis of compound 11a.

Synthesis of novel galeterone derivatives and evaluation of their in vitro activity against prostate cancer cell lines.

Prostate cancer is one of the main causes of male cancer-related deaths worldwide and the suppression of androgen receptor signalling is established as an effective strategy for the treatment. A series of galeterone analogues including several steroid-fused azacycles, as well as 17-(benzimidazol-1-ylimino), 16α-(benzimidazol-2-ylamino), and 16α-(benzothiazol-2-ylamino) steroid derivatives, were synthesized and tested against prostate cancer cell lines. Candidate compound 3f was shown to reduce AR-regulated transcription in a dose-dependent manner in nanomolar ranges and suppress expression of AR-regulated proteins Nkx3.1 and PSA in 22Rv1-ARE14 and VCaP cancer cell lines. Flexible docking study revealed similar position of 3f within AR binding site in comparison of galeterone even with stronger binding energy.

Access to 27-Nortomatidine and 27-Norsoladulcidine Derivatives.

Synthesis of (22 R)- and (22 S)-27-norspirosolane alkaloids from tigogenin, epismilagenin, and smilagenin is described. The alkaloids were prepared from readily available dinorcholanic lactones via their reaction with 4-chlorobutyllithium followed by substitution of chloride with azide and reductive N-cyclization under the Staudinger conditions.

Two-step Synthesis of Solasodine Pivalate from Diosgenin Pivalate.

A two-step synthesis of solasodine pivalate from diosgenin pivalate is described. The key transformation involves the reaction of diosgenin pivalate with benzyl carbamate (CbzNH2) promoted by TMSOTf. During the reaction the F-ring of the spiroketal moiety opens up with a simultaneous introduction of a Cbz-protected amino group in position 26. A one-pot deprotection of 26-amine with AcBr/BuOH followed by the N-cyclization affords solasodine pivalate in 45% overall yield.

Synthesis of steroidal 1,2- and 1,3-diamines as ligands for transition metal ion complexation.

Two series of cholestane-based diamines (1,2 and 1,3) were synthesized using simple and efficient procedures. The convenient substrates for these syntheses were cholesteryl mesylate and tosylate, which were converted to appropriate amines via easily obtained azides. The final diamines were prepared using a substitution reaction with bromoacetonitrile (in the case of 1,2-diamines) or condensation with acrylonitrile (in the case of 1,3-diamines), followed by the reduction of intermediate aminonitriles. Furthermore, the other two amines were synthesized from 16-dehydropregnenolone acetate using aza-Michael addition as a key step. Some of the diamines were subjected to complexation reactions with K2PtCl4 to form steroidal analogs of cisplatin. The synthetic methods tested in this work will allow us to prepare other cisplatin derivatives based on steroids showing anticancer properties themselves.

Synthesis and antimicrobial properties of steroid-based imidazolium salts.

Imidazolium salts reveal interesting biological properties, especially regarding antitumor and antimicrobial activities. Two series of imidazolium salts based on steroids were obtained in an efficient and convenient synthesis. They were biologically tested to evaluate their antibacterial and antifungal properties. The activities of new salts, especially in relation to Gram-positive bacterial strains are comparable to the activities of known antibiotics. The most promising activity was that against C. albicans, which exceeded the antifungal activity of commonly used drugs. Some of the new salts exhibited improved antifungal activities against phytopathogenic fungi: B. cinerea and C. beticola. Our research showed that new compounds could be potentially useful as antifungal antibiotics or inhibiting agents against pathogenic fungi.

Revision of the Structure of N, O-Diacetylsolasodine. Unusual Epimerization at the Spiro Carbon Atom during Acetylation of Solasodine.

The steroidal alkaloid solasodine (1) undergoes inversion of configuration at the C-22 spiro atom when treated with acetic anhydride-pyridine at ambient temperature. The basic solvolysis of the N, O-diacetyl derivative (2) reverses the reaction, yielding the starting solasodine (1). The mechanisms of both processes (acetylation and deacetylation) were studied in terms of possible reaction pathways.