Efficient trans-diaxial hydroxylation of Δ5-steroids

Semi-Synthesis and Biological Evaluation of 25(R)-26-Acetoxy-3β,5α-Dihydroxycholest-6-One

Previously, we identified a series of steroids (1–6) that showed potent anti-virus activities against respiratory syncytial virus (RSV), with IC50 values ranging from 3.23 to 0.19 µM. In this work, we first semi-synthesized and characterized the single isomer of 5, 25(R)-26-acetoxy-3β,5α-dihydroxycholest-6-one, named as (25R)-5, in seven steps from a commercially available compound diosgenin (7), with a total yield of 2.8%. Unfortunately, compound (25R)-5 and the intermediates only showed slight inhibitions against RSV replication at the concentration of 10 µM, but they possessed potent cytotoxicity activities against human bladder cancer 5637 (HTB-9) and hepatic cancer HepG2, with IC50 values ranging from 3.0 to 15.5 µM without any impression of normal liver cell proliferation at 20 µM. Among them, the target compound (25R)-5 possessed cytotoxicity activities against 5637 (HTB-9) and HepG2 with IC50 values of 4.8 µM and 15.5 µM, respectively. Further studies indicated that compound (25R)-5 inhibited cancer cell proliferation through inducing early and late-stage apoptosis. Collectively, we have semi-synthesized, characterized and biologically evaluated the 25R-isomer of compound 5; the biological results suggested that compound (25R)-5 could be a good lead for further anti-cancer studies, especially for anti-human liver cancer.

Triterpene and Steroids from Ludwigia abyssinica A. Rich (Onagraceae) Displayed Antimicrobial Activities and Synergistic Effects with Conventional Antibiotics

Difficulties encountered in treating drug-resistant pathogens have created a need for new therapies. Synergistic combinations of antibiotics are considered as ideal strategies in combating clinical and multidrug-resistant (MDR) infections. In this study, the antimicrobial activities of triterpenes and steroids from Ludwigia abyssinica A. Rich (Onagraceae) and their combined effects with antibiotics were assessed. The associations between plant constituents and antibiotics were evaluated by determining their fractional inhibitory concentrations (FICs). Sitost-5-en-3β-ol formiate (1), 5α,6β-dihydroxysitosterol (2), and maslinic acid (3) were isolated from the L. abyssinica ethyl acetate (EtOAc) extract. The EtOAc extract, compounds 1, 2, and 3 (MIC = 16-128 µg/mL) would be the best antibacterial and antifungal agents. The antimicrobial activities of amoxicillin were relatively weak against MDR Escherichia coli and Shigella flexneri and significant against Staphylococcus aureus ATCC 25923. However, when used in association with plant constituents, it displayed an interesting synergistic effect. Among plant components-antibiotic combinations, the EtOAc extract and compound 1 (steroid) showed a synergistic effect with amoxicillin/fluconazole against all the tested microorganisms whereas the association of compound 3 (triterpenoid) and amoxicillin/fluconazole displayed an additive effect against Shigella flexneri and Escherichia coli and a synergistic effect on Staphylococcus aureus, Cryptococcus neoformans, Candida tropicalis, and Candida albicans ATCC 10231. Overall, the results of the present study demonstrated antibacterial and antifungal activities of extracts and compounds isolated from L. abyssinica. The findings of the current study also showed that the potency of antibiotics was improved when screened in combination with L. abyssinica components, supporting the drug combination strategy to combat antimicrobial resistance.

A new ergostane derivative from the leaves of Heynea trijuga Roxburgh

During the course of searching for structurally interesting and bioactive compounds, a further chemical investigation of the leaves of Heynea trijuga Roxburgh was performed, which led to the isolation of a new ergostane derivative, named 3β, 4β, 20S-trihydroxyergosta-5, 24(28)-dien-16-one (1), together with five known sterides (3β, 23S)-ergosta-5, 24(28)-diene-3, 23-diol (2), ergosta-5, 24(28)-diene-3β-diol (3), stigmast-5-ene-3β, 7α-diol (4), sitoindoside I (5) and stigmast-3β, 5α, 6β-triol (6). The structure of the new compound was elucidated using a combination of 1 D, 2 D NMR techniques and HR-EI-MS analyses. All the compounds were evaluated for cytotoxic activity against tumor cell line BEL-7402 by MTT method.

Sodium Hypochlorite Pentahydrate as a Reagent for the Cleavage of trans-Cyclic Glycols

Sodium hypochlorite pentahydrate (NaOCl·5H₂O) can be used toward the efficient glycol cleavage of trans-cyclic glycols, which are generally resistant to this transformation. Interestingly, the reaction of cis-cyclic glycols with NaOCl·5H₂O is slower than that observed for the corresponding trans-isomer. This trans selectivity is in sharp contrast to traditional oxidants used for glycol cleavage. Acyclic glycols can also react efficiently with NaOCl·5H₂O to form their corresponding carbonyl compounds in high yield.

Three new iridoids from two Viburnum species

Three new iridoids, 10-deacetyl suspensolide A aglycone (1), 7-deacetyl suspensolide A aglycone (2), and 7,10-dideacetyl suspensolide A aglycone (3), were isolated from two species of Viburnum. Their structures were elucidated on the basis of spectroscopic methods, including 1D and 2D NMR techniques. Compound 2 exhibited moderate anti-inflammatory activity against NO production in LPS-stimulated RAW 264.7 cells with IC50 of 17.2 μM.

Oxidation of Olefins with Benzeneseleninic Anhydride in the Presence of TMSOTf

A new oxidizing system for olefins, consisting of benzeneseleninic anhydride and trimethylsilyl triflate, was studied. The highly reactive benzeneseleninyl cation is presumably formed under these conditions. It has been shown that different products are formed with this species depending on the specific structure of olefin. The 1,1-disubstituted olefins afforded mostly α,β-unsaturated carbonyl compounds. The sterically encumbered tri- or tetrasubstituted olefins yielded 1,2- or 1,4-dihydroxylated products, presumably via four-membered cyclic intermediates.

Quantitative and stereospecific dihydroxylations of δ(5)-steroids: a green synthesis of plant growth hormone intermediates

Dihydroxylated Δ(5)-steroids are key intermediates in preparing steroids bearing a 5α-hydroxy-6-oxo moiety, which are plant growth hormones. Quantitative and stereospecific dihydroxylations of Δ(5)-steroids have been realized, using H2O2 catalyzed by KI and H2SO4 at 80 °C in aqueous dioxane. The workup consisted only of concentrating the solvents and filtering the products; no chromatography was needed. The reaction conditions tolerate various functional groups on the Δ(5)-steroids. A mechanism for this reaction is proposed and the reason that the reaction is quantitative and stereospecific is explained.

3β,5α,6β-Oxygenated sterols from the South China Sea gorgonian Muriceopsis flavida and their tumor cell growth inhibitory activity and apoptosis-inducing function

Three new polyhydroxysterols, named muriflasteroids A-C (1-3) were isolated from the South China Sea gorgonian Muriceopsis flavida, together with sixteen known analogs, cholest-3β,5α,6β-triol,3β-acetate (4), 5α-methoxycholest-3β,6β-diol (5), (22E)-cholest-22-en-3β,5α,6β-triol (6), cholest-3β,5α,6β-triol (7), (22E)-24-norcholest-22-en-3β,5α,6β-triol (8), (22E,24S)-ergost-22-en-3β,5α,6β-triol (9), ergost-24(28)-en-3β,5α,6β-triol (10), (22E)-cholest-7,22-dien-3β,5α,6β-triol (11), cholest-7-en-3β,5α,6β-triol (12), (22E)-24-norcholest-7,22-dien-3β,5α,6β-triol (13), ergost-7,24(28)-dien-3β,5α,6β-triol (14), (22E,24R)-ergost-7,22-dien-3β,5α,6β-triol (15), (22E)-cholest-22-en-1β,3β,5α,6β-tetrol (16), (22E)-24-norcholest-22-en-1β,3β,5α,6β-tetrol (17), cholest-1β,3β,5α,6β-tetrol (18), and (24ξ)-ergost-1β,3β,5α,6β-tetrol (19). The structures of the new compounds were elucidated by detailed spectroscopic analysis in combination with comparison of reported data. All the compounds are reported for the first time from the animal. In the bioassay in vitro, these compounds exhibited different levels of growth inhibition activity against A549 and MG63 cell lines. In particular, compound 18 displayed a considerable activity, being similar as that of positive control adriamycin. An annexin V analysis indicated that compounds 7 and 18 can significantly induce apoptosis in A549 cell, and compound 7 is more potent in the induction of apoptosis. Preliminary structure-activity analysis suggests that the acetylation on 3-OH and appearance of Δ⁷ may decrease the activity while substitution of 1-OH and the nature of side chain may also play an important role in the activity. Methylation of 5-OH contributed a little to the activity.

Bismuth compounds in medicinal chemistry

In recent years, the chemical potential of bismuth and bismuth compounds has been actively exploited. Bismuth salts are known for their low toxicity, making them potential valuable reagents for large-scale synthesis, which becomes more obvious when dealing with products such as active pharmaceutical ingredients or synthetic intermediates. Conversely, bismuth compounds have been widely used in medicine. After extensive use in the treatments of syphilis and other bacterial infections before the advent of modern antibiotics, bismuth compounds remain important for the treatment of several gastrointestinal disorders and also exhibit antimicrobial properties and cytotoxic activity, among others. This review updates relevant advances in the past few years, concerning the application of bismuth reagents and catalysts in innovative synthetic processes for the preparation of compounds of medicinal interest, as well as the preparation, biological evaluation and potential medicinal uses of bismuth compounds.

5α,6α-Ep-oxy-7-norcholestan-3β-yl acetate

The title cholestan, C(28)H(46)O(3), was prepared by epoxidation of 7-norcholest-5-en-3β-yl acetate and crystallized by slow evaporation from an ethano-lic solution. All rings are trans fused. The 3β-acetate and the 17β-cholestane side chain are in equatorial positions. The mol-ecule is highly twisted due to its B-nor characteristic. A quantum chemical ab-initio Roothaan Hartree-Fock calculation of the equilibrium geometry of the isolated mol-ecule gives values for bond lengths and valency angles in close agreement with the experimental ones.

Androstane-3β,5α,6β,17β-tetrol tri-hydrate

The title hydrated tetrol, C(19)H(32)O(4)·3H(2)O, was synthesized by stereoselective reduction of the compound 3β,5α,6β-trihy-droxy-androstan-17-one. All rings are fused trans. The organic mol-ecules are connected head-to-tail along the c axis via O-H⋯O hydrogen bonds. Layers of water mol-ecules in the ab plane inter-connect these chains. A quantum chemical ab initio Roothan Hartree-Fock calculation of the isolated mol-ecule gives values for the mol-ecular geometry close to experimentally determined ones, apart from the C-O bond lengths, whose calculated values are significantly smaller than the measured ones, probably a consequence of the involvement of the C-OH groups in the hydrogen-bonding network.

3β,5α,6β-Trihy-droxy-androstan-17-one

The title compound, C(19)H(30)O(4), is an androstan-17-one derivative synthesized from the dehydro-epiandrosterone through a sequential addition of an oxidant, followed by a trans-diaxial opening of the epoxide generated, with Bi(OTf)(3) (OTf is trifluoro-methane-sulfonate). The six-membered rings have a slightly flattened chair conformation, while the five-membered ring adopts a 14-α envelope conformation. All rings are trans fused. In the crystal, the mol-ecules are connected by O-H⋯O hydrogen bonds involving the hydroxyl and carbonyl groups, forming a three-dimensional network. A quantum mechanical ab initio Roothan Hartree-Fock calculation of the free mol-ecule gives bond lengths, valency angles and ring torsion angles of the free molecule at equilibrium geometry (energy minimum) close to the experimental values.

Bismuth(III) reagents in steroid and terpene chemistry

Steroid and terpene chemistry still have a great impact on medicinal chemistry. Therefore, the development of new reactions or “greener” processes in this field is a contemporaneous issue. In this review, the use of bismuth(III) salts, as “ecofriendly” reagents/catalysts, on new chemical processes involving steroids and terpenes as substrates will be focused. Special attention will be given to some mechanistic considerations concerning selected reactions.