Pregnenolone Acetate Research Articles

D-ring substituted 1,2,3-triazolyl 20-keto pregnenanes as potential anticancer agents: Synthesis and biological evaluation

A facile synthesis of 21-triazolyl derivatives of pregnenolone and their potential antitumour activity is reported. The scheme involves the transformation of the starting pregnenolone acetate into pregnenolone, conversion of pregnenolone to 21-bromo pregnenolone and finally the one-pot, two-step in situ conversion of the bromo derivative to the 21-triazolyl pregnenolone using the ‘click chemistry’ approach. These derivatives were screened for their anticancer activity against seven human cancer cell lines. The compounds especially 5a, 5b, 5c, 5e, 5g and 5h exhibited significant anticancer activity with compound 5e as the most active in this study.

Studies on novel D-ring substituted steroidal pyrazolines as potential anticancer agents

An efficient and facile synthesis of 17-pyrazolinyl derivatives of pregnenolone and their evaluation as potential anticancer agents against various human cancer cell lines are reported. The scheme involves the transformation of the starting pregnenolone acetate into pregnenolone, conversion of pregnenolone to the corresponding benzylidine derivatives and finally the conversion of this derivative to the stable steroidal 17-pyrazoline. Various compounds 4b, 4c, 4e, 4f, 4h and 4j showed significant cytotoxic activity especially against HT-29, HCT-15, 502713 cell lines.

Stereoselective Synthesis of Methyl Spongoate, a New Steroid with Potent Antitumor Activities

The stereoselective synthesis of methyl spongoate, a naturally occurring new steroid derivative with an unusual C-20 methoxycarbonyl group and potent antitumor activities, was achieved starting from the commercially available pregnenolone acetate in 11% overall yield.

Microbial Hydroxylation of Pregnenolone Derivatives

Pregnenolone and pregnenolone acetate were incubated with the fungi Cunninghamella elegans, Rhizopus stolonifer and Gibberella fujikuroi. Incubation of with C. elegans yielded metabolites, 3beta,7beta,11alpha-trihydroxypreg-5-en-20-one, 3beta,6alpha,11alpha,12beta,15beta-pentahydroxypreg-4-en-20-one and 3beta,6beta,11alpha-trihydroxypreg-4-en-20-one, while incubation with G. fujikuroi yielded two known metabolites, 3beta,7beta-dihydroxypregn-5-en-20-one and 6beta,15beta-dihydroxypreg-4-ene-3,20-dione. Metabolites and were found to be new. Fermentation of by C. elegans yielded four known oxidative metabolites, androsta-1,4-diene-3,17-dione, 6beta,15beta-dihydroxyandrost-4-ene-3,17-dione and 11alpha,15beta-dihydroxypreg-4-ene-3,20-dione. Fermentation of with R. stolonifer yielded two known metabolites, 11alpha-hydroxypreg-4-ene-3,20-dione and. Compounds were screened for their cholinesterase inhibitory activity in a mechanism-based assay.

The Preparation of 21,21‐Dimethylprogesterone.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The Preparation of 21,21-Dimethylprogesterone

The kinetically controlled alkylation of pregnenolone acetate has been used to prepare the 21,21-dimethyl analogue which was then converted into 21,21-dimethylprogesterone.

Synthesis and GABA A receptor activity of 6-oxa-analogs of neurosteroids

The 6-oxasteroids 3α-hydroxy-6-oxa-5α-pregnan-20-one ( 3) and 3α-hydroxy-6-oxa-5β-pregnan-20-one ( 4) were obtained from pregnenolone acetate via the corresponding (5α or 5β) 3β,20β-diacetoxy-6-oxa-pregnane. Both steroids showed ca. 100-fold reduced potency for modulating [ 3H]flunitrazepam, [ 3H]muscimol or [ 35S]TBPS binding to the GABA A receptor when compared to their natural carbon analogs 3α-hydroxy-5α-pregnan-20-one ( 1) and 3α-hydroxy-5β-pregnan-20-one ( 2).

Reduction of Steroidal Ketones and Enones by Sodium Dithionite in Presence of Phase Transfer Catalyst

Abstract Sodium dithionite has been effectively used in the reduction of steroidal ketones and enones with remarkable selectivity and high yields under phase transfer catalysis (PTC) conditions to give alcohols and ketones respectively. An application of these selectivities is demonstrated by reducing an important steroid intermediate 16-dehydropregnenolone acetate to pregnenolone acetate in very high yields.

Catalytic β-stereospecific epoxidation of unsaturated steroids by trans-dioxoruthenium(VI)tetramesitylporphyrin. Stereochemical grounds for the β-diastereofacial selection

The catalytic epoxidation by dioxygen with trans-dioxoruthenium(VI)tetramesitylporphyrin [Ru(O)2(tmp)] of the acetic esters of cholesterol, 3-epicholesterol and isocholesterol,† as well as of the 7α-epimer of the latter, is β-stereospecific. Substitution by a methyl group on C-6 of pregnenolone acetate results in reduced reactivity towards catalytic epoxidation and lower β-stereoselectivity. 19-Norsterol esters bearing a double bond at C-8–C-14 or C-14–C-15 are inert towards O2–RU(O)2(tmp) epoxidation. The variable reactivity of these sterol ester substrates is explained by a transition state in which the steroid nucleus approaches the ruthenium–oxo bond approximately perpendicular to the porphyrin ring. The β-selectivity of Δ5-sterol ester epoxidation is accounted for in terms of this transition state geometry which provides a good fit between the porphyrin catalyst and the steroid substrate when the β-side faces the oxo ligand. On the other hand, reaction on the α-side involves unfavourable steric interactions between axial hydrogen atoms on C-3 and C-7 of the substrate and the porphyrin ring and a mesityl substituent of the catalyst, respectively. The crystal and molecular structures of cholesteryl ethyl carbonate and of its 5,6β-epoxide have been determined by single-crystal X-ray diffraction. The overall conformation of the steroid nucleus is nearly planar in the cholesteryl ester, while it is bent at the junction between rings A and B in the 5,6β-epoxide. This change from pseudo-trans- to cis-stereochemistry of the A–B ring junction upon epoxidation is proposed to amplify the β-diastereofacial selection. Variable temperature 1H NMR spectra indicate that in CD2Cl2 solution the 5,6β-epoxide (not the 5,6α-epoxide) of the cholesteryl acetate coordinates the ruthenium atom of Ru(CO)(tmp) with a nearly perpendicular geometry. These results corroborate the orthogonal substrate approach and the steric origin of the β-stereospecificity in Ru(O)2(tmp)-catalysed steroid epoxidations.

Dehydroepiandrosterone therapeutics: Acetylation of DHA in mouse liver

This investigation was designed to evaluate the possibility that the therapeutic benefits of dehydroepiandrosterone (DHA)-feeding in mice is mediated by (1) a metabolite of DHA formed in liver or (2) by way of the obligatory hepatic metabolism of DHA fed in large amounts. We found that the pattern of metabolism of DHA is strikingly different when DHA in low (tracer) quantities is incubated with mouse liver compared with that found when DHA in high concentrations is incubated with this tissue. In the former case, the principal metabolites are sulfoconjugates and other polar compounds, e.g. hydroxylated products. In the case of DHA metabolism when the substrate is present in high concentrations (1–100 μM), the principal metabolite formed is Δ 5-androstenediol. And in this case, there is the formation of very nonpolar metabolites, which we have identified as the acetates of DHA and Δ 5-androstenediol. We find further that the acetates are formed by a transacetylation mechanism in which performed acetylated compounds, e.g. pregnenolone acetate and ethyl acetate, can serve directly as co-substrates; but (at least in short-term incubations), Na + -acetate and acetyl CoA do not serve as co-substrates. We suggest that the therapeutic benefits of DHA-feeding in mice may be, in part, the result of alterations in hepatic intermediary metabolism that is obliged by the metabolism of DHA when this otherwise inert agent is fed in large amounts. Thus, DHA-feeding may serve to cause changes similar to those that are beneficial or therapeutic with dietary manipulations including caloric restriction.

Detection of deuterium labelling by two-dimensional 1H,13C nuclear magnetic resonance shift correlation with 2H decoupling

Methylene groups that are stereospecifically labelled with deuterium can be easily observed using deuterium-decoupled 2-dimensional proton/carbon nmr shift correlation spectroscopy in either normal or CH-selective mode. Application of the technique to [3-2H]camphors 2, 3, and 4 shows that overlap of other 13C resonances does not interfere with the 2H detection. Such experiments with [3-2H]-N-benzoylphenylalanine methyl esters 6 and 7 demonstrate that identification of labelled diastereotopic hydrogens can be done if they are separated by 0.1 ppm in the 1H nmr spectrum. Fully deuterated carbons (e.g., CD3 methyl, CD2 methylene, CD methine) cannot be observed by this approach, as seen by the study of pregnenolone acetate (9) randomly deuterated at C-17 and C-21. The technique is ideal for cases with extensive overlap of other proton and carbon resonances because high chemical shift dispersion in two dimensions separates the signals of interest. This nmr method was used to show that hydrogenation of cholesteryl acetate (10) with deuterium gas and palladium catalyst exchanges the C-7 α-hydrogen to give 12. The detection limit is estimated at 10% deuterium per site unless 13C-labelled compounds are used.

ChemInform Abstract: Convenient Preparative Routes to 19‐Hydroxy, 19‐Oxo‐, 19‐Oic, and 19‐Nor‐deoxy‐ corticosterone.

AbstractStarting from pregnenolone acetate (I) the title compounds (V), (X), (XI) and (XIV) are synthesized by the pathways shown in the scheme.

Convenient preparative routes to 19-hydroxy, 19-oxo-, 19-oic-, and 19-nor-deoxycorticosterone

Practical synthetic routes to 19-hydroxy-, 19-OXO-, 19-oic-, and 19-nor-deoxy-corticosterone were developed. 19-Hydroxydeoxycorticosterone (11) and its 21-acetate 10 were first prepared by two routes via O-protected 19-oxygenated intermediates 6 and 17 starting from readily available pregnenolone acetate (1) and dehydroepiandrosterone acetate (12). The key step in the first route is the application of Henbest acetoxylation at C-21 to the enamine 7 derived from 6. The second route involves introduction of a hydroxyacetyl side chain at C-17 starting with base-catalyzed condensation of 17 with methoxyacetic ester. 19-Oxo- and 19-oic-deoxycorticosterone (23 and 25) and their 21-acetates 22 and 24 were obtained via chromium trioxide oxidation of 10 under different controlled conditions. Alkaline hydrolysis of 22 under decarbonylation led to 19-nor-deoxycorticosterone(26). Alternatively, a short-step synthesis of the latter steroid from estrone methyl ether (27) was achieved by utilizing the same procedure for construction of the corticoid side chain.

Metabolism of steroid acetates by Streptomyces albus

Fermentation of 16-dehydropregnenolone acetate ( 1a) with Streptomyces albus yielded 16-dehydropregnenolone ( 1b) and 16-dehydroprogesterone ( IIa). Similar incubation of pregnenolone acetate ( Ic) with the strain afforded pregnenolone ( Id), progesterone ( IIb) and 20α-hydroxy progesterone ( IIc) while dehydroepiandrosterone acetate ( IIIa) under the conditions was converted to dehydroepiandrosterone ( IIIb), androstenedione ( IVa) and testosterone ( IVc). The strain was also capable of converting testosterone acetate ( IVb) having the 17-acetoxy function in the 5-membered d-ring to testosterone ( IVc) and androstenedione ( IVa). All the products were identified by the application of various chemical and spectrometric techniques.

Evidence for the existence of a C25-sesterterpene pathway of steroidogenesis not involving cholesterol as an obligatory intermediate.

Previous in vitro studies had indicated the possibility of steroidogenesis through a C25-sesterterpene pathway in which squalene and cholesterol are not required as obligatory intermediates. To investigate whether such a pathway exists in vivo, the precursor role of [7-3H]23,24-dinor-5-cholene-3 beta,20-diol in the in vivo formation of cortisol by the guinea pigs was studied. The [3H]23,24-dinor-5-cholene-3 beta,20-diol was synthesized by reacting [3H]pregnenolone acetate with a Grignard reagent. The product was purified by chromatography and its radiochemical purity was established by the isotope dilution technique. In the first experiment a total of 134 X 10(6) dpm of [3H]23,24-dinor-5-cholene-3 beta,20-diol was injected subcutaneously into three guinea pigs. Urine was collected for 8 days and was pooled. Only 12% of the administered dose was excreted in the urine. The urine was extracted and a neutral extract (3 X 10(6) dpm) was obtained. From this extract 2.3 mg of cortisol containing 2.9 X 10(4) dpm was isolated. Radiochemical purity of the isolated cortisol was established by the isotope dilution technique. Radiochemical purity was further confirmed by conversion to cortisol 21-acetate and subsequently to 11 beta-hydroxyandrost-4-ene-3,17-dione and recrystallization to constant specific activity. The results of this experiment were confirmed by repeating the experiment with a higher specific activity [3H]23,24-dinor-5-cholene-3 beta,20-diol. These results indicate that the C25-sesterterpene pathway is a possible in vivo alternate pathway of steroidogenesis, not involving either squalene or cholesterol as obligatory intermediates.

Effect of various xenobiotics and steroids on aryl hydrocarbon hydroxylase activity of intestinal and hepatic microsomes from male rats.

The effects of four solvents and 37 xenobiotics and endogenous steroids on intestinal and hepatic microsomal aryl hydrocarbon hydroxylase (AHH) activity were determined. In general, hepatic AHH was more sensitive than intestinal AHH to inhibition by a wide variety of xenobiotics. Acetone, ethanol, dimethyl formamide, triamcinolone acetonide, 17 alpha-propyltestosterone, metronidazole, cimetidine and butylated hydroxyanisole (BHA) activated or stimulated intestinal AHH activity while inhibiting hepatic AHH activity at the same concentrations. Ethoxyquin, progesterone, pregnenolone acetate, deoxycorticosterone acetate, tamoxifen and SKF 525-A exerted markedly different concentration-dependent inhibitions of intestinal and liver AHH activities. The most potent inhibitors of AHH activity were captan, BHA, chlorpromazine, thioridazine, disulfiram and menadione. The ability of steroids to inhibit AHH activity correlated well with lipophilicity.

Synthesis of (20R)-3?-acetoxy-?5-bisnorcholenal

We have prepared oxirane (IV) by reaction of pregnenolone acetate (II) with fimdyldofium in yields of up to 90%; treatment with BF3 etherate quantitatively isomerized it to (20R)-3β-acetoxy-Δ5-bisnorcholenal (III).

Structural analogs of lα,25-dihydroxycholecalciferol: Preparation and biologial assay of 1α-hydroxypregnacalciferol

The synthesis of lα-hydroxypregnacalciferol, a side chain analog of lα,25-dihydroxycholecalciferol (1α,25-dihydroxyvitamin D 3), is described. Pregnenolone acetate was converted in five steps to 5-pregnen-lα,3β-diol. Conversion of the diol to pregna-5,7-diene-lα,3β diol diacetate followed by ultraviolet irradiation gave the corresponding provitamin derivative. Thermal isomerization, hydrolysis and chromatography then furnished the desired analog, lα-hydroxypregnacalciferol. The compound was tested in vivo for its effect on intestinal calcium transport, serum calcium and phosphate levels and bone calcification, and in vitro for its effect on bone resorption. When given to intact rats, either as a single dose or in repeated daily doses, the analog even at high dose levels, exhibited no biological activity. The compound stimulated bone resorption in vitro , but only at high concentrations.

Synthesis of 3β,14β,19-Oxygenated Cardenolides

The synthesis of 3β,14β,19-oxygenated and of 3β,19-oxygenated-14-dehydro cardenolides from the bulk steroid pregnenolone acetate 1a is reported. The 19-oxygenated cardenolides which have been prepared include coroglaucigenin esters 4e and 4f and corotoxigenin acetate 4g. Coroglaucigenin and corotoxigenin occur in nature as glycosides in a number of plant species. In the synthetic scheme developed, successive transformations of the 3β-acetoxy-10β-methyl-5-ene moiety of 1a afford 19-hydroxy- or acyloxy-14-enes via 19-hydroxy-8(14)-enes and 8,19-oxido-14-enes.

Synthesis and study of the labeling of pregnenolone and progesterone specifically tritiated at the 17 position.

The action of tritiated acetic acid on 17-bromopreg-[3 H] nenolone acetate treated with zinc metal dust produces 17 pregnenolone acetate which is then hydrolyzed to form 17 [3 H] pregnenolone. The flavobacterium dehydrogenans transforms the 17-bromopregnenolone into 17-bromoprogesterone which can also be tritiated by tritiated acetic acid to obtain 17 [3 H] progesterone. The study of the label distribution by different analytic techniques (I.R., nuclear magnetic resonance, mass spectrometry) as well as the. chemical and selective biochemical reactions indicate a specific labeling higher than 85% on the 17 position.