Application of olefin metathesis in the synthesis of steroids

1H NMR Analysis of the Metathesis Reaction between 1-Hexene and (E)-Anethole Using Grubbs 2nd Generation Catalyst: Effect of Reaction Conditions on (E)-1-(4-Methoxyphenyl)-1-hexene Formation and Decomposition

The metathesis of 1-hexene and (E)-anethole in the presence of Grubbs 2nd generation catalyst was monitored by in situ 1H NMR spectroscopy at different temperatures (15 °C, 25 °C, and 45 °C) and anethole mol fractions (XAnethole ≈ 0.17, 0.29, 0.5, 0.71, 0.83). Time traces confirmed the instantaneous formation of (E)-1-(4-methoxyphenyl)-1-hexene, the cross-metathesis product. A maximum concentration of (E)-1-(4-methoxyphenyl)-1-hexene is reached fairly fast (the time depending on the reaction conditions), and this is followed by a decrease in the concentration of (E)-1-(4-methoxyphenyl)-1-hexene due to secondary metathesis. The maximum concentration of (E)-1-(4-methoxyphenyl)-1-hexene was more dependent on the XAnethole than the temperature. The highest TOF (3.46 min−1) was obtained for the reaction where XAnethole was 0.16 at 45 °C. The highest concentration of the cross-metathesis product was however achieved after 6 min with an anethole mol fraction of 0.84 at 25 °C. A preliminary kinetic study indicated that the secondary metathesis reaction followed first order kinetics.

Fluorine-containing ruthenium-based olefin metathesis catalysts

The review summarizes literature data on the methods for the introduction of fluorine atoms and fluoralkyl groups into different ligands to construct metathesis-active ruthenium carbene complexes. It also analyzes the influence of fluorinated ligands on the catalytic activity of the complexes. The choice, structure and positions of fluorinated substituents in NHC ligands are generally dictated by the desire to increase the electrophilicity of the ruthenium atom due to the electron-withdrawing effect of fluorine atoms and fluoroalkyl groups, resulting, as a rule, in an increase in the activity of the ruthenium complex. In catalysts with unsymmetrical fluorine-containing NHC ligands, there is a possibility of additional Ru–F coordination, making the complexes much more stable and, consequently, more active. The presence of fluorine in chelating alkylidene ligands provides an increase in the catalyst initiation rate due to a weakening of the ruthenium – heteroatom bond. Besides, the introduction of polyfluoroalkyl groups into ligands solves the problem of catalyst recovery using fluorous biphasic systems for reuse.

The bibliography includes 172 references.

Organotin derivatives of cholic acid induce apoptosis into breast cancer cells and interfere with mitochondrion; Synthesis, characterization and biological evaluation

Organotin(IV) derivatives of cholic acid (CAH) with the formulae R3Sn(CA) (R = Ph- (1), n-Bu- (2)) and R2Sn(CA)2 (R = Ph- (3), n-Bu- (4) and Me- (5)) were synthesized. The compounds were characterized in solid state by melting point, FT-IR, 119Sn Mössbauer, X-ray fluorescence (XRF) spectroscopy and in solution by 1H NMR, UV-Vis spectral data and by Electrospray Ionisation Mass spectrometry (ESI-MS), High Resolution Mass spectrometry (HRMS), and atomic absorption analysis. The in vitro bioactivity of 1-5 against human breast adenocarcinoma cancer cells MCF-7 (positive to hormone receptors) and MDA-MB-231 (negative to hormone receptors) reveal that triorganotin derivatives 1-2 exhibit significantly stronger activity than the corresponding diorganotin ones. Compound 5 is inactive against both cell lines at the concentrations tested. Triorganotins 1-2 inhibit selectively MCF-7 than MDA-MB-231 cells, suggesting hormone mimetic behavior of them. Organotins 1-4 inhibit both cancerous cell lines, stronger than cisplatin which rise up to 55-fold against MCF-7 and 170-fold against MDA-MB-231. The in vitro toxicity of 1-4 was evaluated on normal human fetal lung fibroblast cells (MRC-5), while their genotoxicity in vitro by micronucleus assay (MN). Moreover, the in vivo toxicity of 1-4 was tested by Artemia salina assay and their in vivo genotoxicity with Allium cepa test. The mechanism of action of 1-4 against MCF-7 was clarified in vitro by the means of cell morphology studies, cell cycle arrest, Acridine Orange/Ethidium Bromide (AO/EB) Staining, mitochondrial membrane permeabilization test and by their binding affinity toward the calf thymus (CT) DNA.

A review on steroid dimers: 2011-2019

The first review article on steroid dimers by Li and Dias in 1997, followed by the second review and a book on steroid dimers by Nahar and Sarker in 2007 and 2012, respectively, covered steroid dimers reported until the end of 2010. Since then, there have been considerable amounts of research carried out on steroid dimers, prompting the need for another comprehensive review on this topic. Therefore, this present review appraises the literature published during the period 2011-2019 on various aspects of steroid dimers, including isolation from natural sources, synthesis and applications. A structured and systematic literature search was performed, using the key words: steroid dimer, steroidal dimer, dimeric steroid, bis-steroid, bis-steroidal conjugates, molecular umbrella, cephalostatins, ritterazines and crellastatins. Several databases like Web of Knowledge, Science Direct, PubMed and Google Scholar were consulted. During the period covered in this review, well over 200 new synthetic steroidal dimers, ring A-ring A connection being the major group, have been reported, only one natural steroid dimer has been isolated, and potential applications of steroid dimers in the treatment of cancers and tumors, and microbial infections have been indicated.

Synthesis of novel vitamin D3 analog with an additional ring annulated to A and seco-B rings

A simple method for the synthesis of yet unknown 5E-vitamin D3 analogs with an additional six-membered ring connecting C-6 and C-19 was developed. Ring-closing metathesis (RCM) was used for efficient formation thereof from the corresponding 5E-isomers of 6-alkenyl vitamin D3 compounds which in turn were prepared from the 6-oxo-3,5-cyclovitamin D3. Reinvestigation of the Grignard reactions of this latter compound as well as the following acid-catalyzed cycloreversions showed discrepancies with the literature data describing the course of such processes.

Efficient synthesis of polysubstituted olefins using stable palladium nanocatalyst: applications in synthesis of tamoxifen and isocombretastatin A4

A phosphine-free stable palladium nanocatalyst was used for an efficient synthesis of polysubstituted olefins from N-tosylhydrazones and aryl iodides. This methodology was successfully utilized in the synthesis of biologically important tamoxifen and isocombretastatin A4. The nanocatalyst was easily recovered and reused without any apparent loss in size and catalytic activity.

Synthesis of various secosteroidal macrocycles by ring-closing metathesis

We set out to describe an efficient and versatile method for preparing secosteroidal macrocycles from cholic acid, via an oxidative ring-expansion/ring-opening sequence and a ring-closing metathesis reaction as the key steps. The characteristic ¹H and ¹³C NMR spectroscopic features of the synthesized compounds are reported.