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 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.

Electrochemical cholesterylation of sugars with cholesteryl diphenylphosphate.

Electrochemical cholesterylation of various sugars with cholesteryl diphenylphosphate was studied. The reaction afforded mono-, di-, tri-, and tetra-cholesterylated products using equivalent amounts of the reagent. The reactions turned out to be completely stereoselective with respect to both sugar and steroid but only partially regioselective - primary and anomeric hydroxyl groups in sugars were the most reactive ones while no substantial differences in reactivity was found for different secondary hydroxyl groups.

3α,5α-Cyclocholestan-6ß-yl ethers as donors of the cholesterol moiety for the electrochemical synthesis of cholesterol glycoconjugates.

3α,5α-Cyclocholestan-6ß-yl alkyl and aryl ethers were proved to be efficient cholesteryl donors in the electrochemical synthesis of glycoconjugates. 3α,5α-Cyclocholestan-6ß-ol (i-cholesterol) and its tert-butyldimethylsilyl ether can also be used for this purpose. The i-cholesterol derivatives show similar reactivities to those of previously studied 3α,5α-cyclocholestan-6ß-thioethers.

Electrochemical synthesis of glycoconjugates from activated sterol derivatives.

Several derivatives of cholesterol and other 3ß-hydroxy-Δ(5)-steroids were prepared and tested as sterol donors in electrochemical reactions with sugar alcohols. The reactions afforded glycoconjugates with sugar linked to a steroid moiety by an ether bond. Readily available sterol diphenylphosphates yielding up to 54% of the desired glycoconjugate were found to be the best sterol donors.

Bis[3α,7α,12α-tris-(4-nitro-benzo-yloxy)-5ß-cholan-24-yl] disulfide-ethyl acetate-n-hexane (4/4/1).

The crystal structure of the title compound, C(90)H(100)N(6)O(24)S(2)·C(4)H(8)O(2)·0.25C(6)H(14), solved and refined against synchrotron diffraction data, contains two formula units in the asymmetric unit with the all-trans n-hexane mol-ecule having half-occupancy and one of the ethyl acetate mol-ecules disordered over two positions. The two symmetry-independent disulfide mol-ecules are assembled by approximate face-to-face and face-to-edge inter-actions between their 4-nitro-benzo-yloxy groups into an inter-twined dimer having a double-helix-type structure. The centrally placed disulfide bridges in the two symmetry-independent mol-ecules exhibit different helicity as shown by the C-S-S-C torsion angles of 71.0 (1) and -92.5 (1)°.

On reactions of steroidal 23-oxo and 23,24-epoxysapogenins with Lewis acids.

The reaction of 23-oxotigogenin acetate with TMSOTf in THF afforded the corresponding bisnorcholanic lactone in 60% yield. The analogous reactions carried out in dichloromethane or benzene gave the rearranged products--the isomeric spirostanic ketone (10-15%) and bisfuran (40-42%). Similar products were also obtained upon treatment of 23,24-epoxysapogenins with BF(3). The epoxides treated with TiCl(4) afforded mostly chlorohydrins and no rearranged products were detected.