Synthesis and cytotoxic effect of pregnenolone derivatives with one or two α,β-unsaturated carbonyls and an ester moiety at C-21 or C-3

Four series of pregnenolone derivatives having one or two α,β-unsaturated carbonyls and an ester moiety at C-21 or C-3 were synthetized to compare their cytotoxicity effect. The final compounds were evaluated on three human cancer cell lines: PC-3 (prostate cancer), MCF-7 (breast cancer), SKLU-1 (lung cancer) and a noncancerous cell line HGF (human gingival fibroblast). Two steroids with a 4-fluorinated benzoic acid ester at C-21 were the most active against lung cancer cell line with IC₅₀ of 13.1 ± 1.2 and 12.8 ± 0.5 μM and showed a low percentage of cytotoxicity for noncancerous cells (27.63 ± 2.3 and 18.39 ± 1.2% in the screening at 50 μM).

Synthesis of 16α-amino-pregnenolone derivatives via ionic liquid-catalyzed aza-Michael addition and their evaluation as C17,20-lyase inhibitors

Aza-Michael addition of 16-dehydropregnenolone was studied in the presence of a basic ionic liquid, [DBU][OAc] as catalyst and solvent. The reaction was carried out using different primary and secondary amines as N-nucleophiles. The products were obtained in moderate to good yields and were characterized by ¹H and ¹³C NMR, MS and IR. The ionic liquid was found to be an efficient and recyclable catalyst that was reused five times. The products were investigated for the inhibition of in vitro C_17,20-lyase activity and displayed moderate inhibitory effect.

New biaryl-chalcone derivatives of pregnenolone via Suzuki-Miyaura cross-coupling reaction. Synthesis, CYP17 hydroxylase inhibition activity, QSAR, and molecular docking study

A new class of steroids is being synthesized for its ability to prevent intratumoral androgen production by inhibiting the activity of CYP17 hydroxylase enzyme. The scheme involved the synthesis of chalcone derivative of pregnenolone 5 which was further modified to the corresponding biaryl-chalcone pregnenolone analogs 16-25 using Suzuki-Miyaura cross-coupling reaction. The synthesized compounds were tested for activity using human CYP17α hydroxylase expressed in Escherichia coli. Compounds 21 was the most active inhibitor in this series, with IC50 values of 0.61μM and selectivity profile of 88.7% inhibition of hydroxylase enzyme. Molecular docking study of 21 was performed and showed the hydrogen bonds and hydrophobic interaction with the amino acid residues of the active site of CYP17.

A new pregnenolone analogues as privileged scaffolds in inhibition of CYP17 hydroxylase enzyme. Synthesis and in silico molecular docking study

A new series of 17-(N-(arylimino)-5-pregnen-3β-ol derivatives 19-32 as well as carboxylate and acrylate analogues of pregnenolone 37-40 were synthesized and evaluated for their inhibitory activity against human CYP17 hydroxylase expressed in Escherichia coli. Compounds 32 and 37 were the most potent analogues in this series, showing inhibition activity with IC50 = 2.11 and 1.29 μM, respectively. However, the analogue 37 revealed a better selectivity profile (83.21% inhibition of hydroxylase), which is a leading candidate for further development. Molecular docking study of 37 showed binding with the amino acid residues of CYP17 through hydrogen bonds and hydrophobic interaction.

Benzylidine pregnenolones and their oximes as potential anticancer agents: synthesis and biological evaluation

The present study reveals the anticancer activity of benzylidine pregnenolones and their oxime derivatives. The synthesis of the analogs of both series is very simple and involves aldol condensation in the first step followed by nucleophillic addition of hydroxylamine across carbonyl in the second step. Quantitative yields of more than 80% are obtained in both the steps. All the compounds were tested for their cytotoxic activities against a panel of six human cancer cell lines. Amongst all the compounds of both the series screened for their cytotoxic activity, compound 3e, 3f and 4e are very potent especially against HCT-15 and MCF-7 cancer cell lines.

The Knoevenagel reactions of pregnenolone with cyanomethylene reagents: synthesis of thiophene, thieno[2,3-b]pyridine, thieno[3,2-d]isoxazole derivatives of pregnenolone and their in vitro cytotoxicity towards tumor and normal cell lines

The reaction of pregnenolone with either 2-aminoprop-1-ene-1,1,3-tricarbonitrile or 3-oxo-3-phenylpropanenitrile gave the Knoevenagel condensation products 3 and 6, respectively. Separation of the E and Z isomeric compounds of 3 and 6 together with their structure elucidation were carried out. Some chemical transformations of the latter products were carried out and the cytotoxicity of the newly obtained products was evaluated against some cancer cell lines and a human normal cell line. The results indicated that compounds 15, 17a, 18 and 20e among the tested compounds showed the highest cytotoxicity against the cancer cell lines.

Rapid microwave assisted synthesis and antimicrobial bioevaluation of novel steroidal chalcones

A novel class of chalconoyl pregnenolones has been prepared via Claisen-Schmidt condensation under microwave activation and solvent free reaction conditions. The compounds were screened for antimicrobial activity against two bacterial strains Bacillus subtilis and Escherichia coli and two fungal strains Aspergillus niger and Candida albicans. Some of the compounds exhibited significant inhibitory activity against the microbial strains. Presence of the α,β-unsaturated carbonyl moiety in the synthesized compounds was found to be essential for the activity as manipulation of the same through epoxidation of the double bond diminished the activity.

Pregnenolone derivatives as potential anticancer agents

Pregnenolone (1) was used as a template to develop new anticancer compounds. Ring-D modification of 1 resulted in the synthesis of benzylidenes 2-17, pyrazolines 18-76, pyrazoles 85-91, hydrazones 77-84, and oximes 92-107 derivatives. The structure of compound 107 was also deduced through single crystal X-ray diffraction studies. The inclusion of furanyl and pyridyl rings to pregnenolone skeleton increases the cytotoxicity of all compounds significantly. Among benzylidene derivatives, only heterocyclic enone 8 (IC50=0.74 μM/mL against HepG2), and 17 (IC50=4.49 μM/mL against HepG2, IC50=5.01 μM/mL against MDA-MB-230 cancer cell line) exhibited a significant activity. The cytotoxicity data of pyrazoline derivatives 18-76 revealed that only furanyl bearing pyrazolines 40, 42-44, 48, and 49 exhibited significant activities. While all (O-carboxymethyl) oximes, hydazones, and pyrazoles derivatives of pregnenolone did not show any significant activity against both the cell lines. Thus the furanyl bearing enone 8 (IC50=0.74 μM/mL against HepG2), and its pyrazoline derivative 48 (IC50=0.91 μM/mL against MDA-MB-230 cancer cell lines) were identified as the most active compounds in all derivatives of pregnenolone.

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.

New 5alpha-reductase inhibitors: in vitro and in vivo effects

The enzyme 5alpha-reductase is responsible for the conversion of testosterone (T) to its more potent androgen dihydrotestosterone (DHT). This steroid had been implicated in androgen-dependent diseases such as: benign prostatic hyperplasia, prostate cancer, acne and androgenic alopecia. The inhibition of 5alpha-reductase enzyme offers a potentially useful treatment for these diseases. In this study, we report the synthesis and pharmacological evaluation of several new 3-substituted pregna-4, 16-diene-6, 20-dione derivatives. These compounds were prepared from the commercially available 16-dehydropregnenolone acetate. The biological activity of the new steroidal derivatives was determined in vivo as well as in vitro experiments. In vivo experiments, the anti-androgenic effect of the steroids was demonstrated by the decrease of the weight of the prostate gland of gonadectomized hamster treated with T plus finasteride or the new steroids. The IC50 value of these steroids was determined by measuring the conversion of radio labeled T to DHT. The results of this study carried out with 5alpha-reductase enzyme from hamster and human prostate showed that four of the six steroidal derivatives (5, 7, 9, 10) exhibited much higher 5alpha-reductase inhibitory activity, as indicated by the IC50 values than the presently used Proscar 3 (finasteride). The comparison of the weight of the hamster's prostate gland indicated that compound 5 had a comparable weight decrease as finasteride. The overall data of this study showed very clearly those compounds 5, 7, 9, 10 are good inhibitors for the 5alpha-reductase enzyme.

Synthesis of [19- 2H3]-analogs of dehydroepiandrosterone and pregnenolone and their sulfates

Deuterated analogs of pregnenolone and pregnenolone sulfate with three atoms of deuterium in position 19 were prepared. The synthetic approach was developed on derivatives of dehydroepiandrosterone, where initial intermediates were well characterized, and then applied to the pregnenolone series. Starting 19-hydroxy compounds were transformed into 3alpha,5-cycloderivatives to simplify the Jones oxidation into the corresponding 19-oic acids. After oxidation, rearrangement to 3-hydroxy-5-enes, and suitable protection, two deuterium atoms were introduced by lithium aluminum deuteride reduction. Mesylate exchange by iodide in the presence of zinc and deuterium oxide added third deuterium atom. Deprotection gave title analogs with about 93-95% content of d3-derivative, the rest was mainly not fully deuterated d2-analogue as followed from the mass spectra analysis. Thus, 3beta-hydroxy[19-2H3]androst-5-en-17-one was prepared in 14 steps from 19-hydroxy-17-oxoandrost-5-en-3beta-yl acetate in 8.9% yield, the analogous sequence in the pregnenolone series gave 3beta-hydroxy[19-2H3]pregn-5-en-20-one in 7.3% yield. Corresponding sulfates were prepared via pyridinium salts in 53 and 57% yields, respectively. Fully assigned NMR data of selected pregnenolone derivatives were given.

Synthesis and evaluation of 17-aliphatic heterocycle-substituted steroidal inhibitors of 17alpha-hydroxylase/C17-20-lyase (P450 17)

In the search for potent inhibitors of P450 17, the key enzyme in androgen biosynthesis, a series of steroidal inhibitors were synthesized and tested toward rat and human P450 17. Small aliphatic heterocycles (aziridine, oxirane, thiirane, diaziridine, diazirine, azetidine) were introduced into the 17beta-position of anstrost-5-en-3beta-ol. After identifying that aziridine is the most suitable functional group to coordinate with the heme iron, modifications of the steroidal skeleton were performed for further optimization. A wide range of inhibitory potencies toward P450 17 were found for the 21 test compounds. The most potent inhibitors toward the human and rat enzyme were aziridine compounds 3 (IC(50) rat: 0.21 microM, K(i) = 3 nM; IC(50) human: 0.54 microM, K(i) = 8 nM), 5 (IC(50) rat: 0.43 microM, K(i) = 7 nM; IC(50) human: 0.29 microM, K(i) = 4 nM), and 8 (21R:21S = 1:1; IC(50) rat: 0.53 microM, K(i) = 9 nM; IC(50) human: 0.40 microM, K(i) = 6 nM) which were more potent than the reference ketoconazole (IC(50) rat: 67 microM; IC(50) human: 0.74 microM). The inhibitory potency depends markedly on the stereochemistry at C20 of the inhibitors. This effect is more pronounced for the rat enzyme. Tested for selectivity, the highly potent inhibitors show poor inhibitory activity toward P450 arom, P450 scc, P450 TxA(2), and 5alpha-reductase. Tested for in vivo activity, 3 and 8 (0.019 mmol/kg) decreased the plasma testosterone concentration in rats by 81% and 84% after 2 h.

Synthesis and evaluation of novel steroidal oxime inhibitors of P450 17 (17 alpha-hydroxylase/C17-20-lyase) and 5 alpha-reductase types 1 and 2

17 alpha-Hydroxylase/C17-20-lyase (P450 17, CYP 17) and 5 alpha-reductase are the key enzymes in androgen biosynthesis and targets for the treatment of prostate cancer and benign prostatic hyperplasia. In the search of inhibitors for both enzymes, 23 pregnenolone- or progesterone-based steroids were synthesized bearing an oxime group connected directly or via a spacer to the steroidal D-ring. Tested for inhibition of human and rat P450 17, some pregnenolone (9, 11, 14) and a series of progesterone compounds (17-20) turned out to be highly active inhibitors of the human enzyme. The most active compound was Z-21-hydroxyiminopregna-5, 17(20)-dien-3 beta-ol (9) showing K(i) values of 44 and 3.4 nM for the human and rat enzymes, respectively, and a type II UV-difference spectrum indicating a coordinate bond between the oxime group and the heme iron. In contrast to the pregnenolones which showed no inhibition of 5 alpha-reductase isozymes 1 and 2, the progesterones 16, 17, 20, 21, and 23 showed marked inhibition, especially toward the type 2 enzyme. Compounds 17 and 20 were identified as potent dual inhibitors of both P450 17 and 5 alpha-reductase. Tested for selectivity, the most potent P450 17 inhibitors 9, 10, and 14 showed no or only marginal inhibition of P450 arom, P450 scc, and P450 TxA(2). Selected compounds were tested for inhibition of the target enzymes using whole-cell assays. Compounds 9-11 strongly inhibited P450 17 being coexpressed with NADPH-P450 reductase in E. coli cells, and 16, 20, and 23 markedly inhibited 5 alpha-reductase expressed in HEK 293 cells. Tested for in vivo activity, 9 (0.019 mmol/kg) decreased the plasma testosterone concentration in rats after 2 and 6 h by 57% and 44%.

Synthesis of the fatty sterol bound protein for a new sterol antibody

For the purpose of applying the particular antibodies as a new diagnostic procedure for atherosclerosis and related diseases, we successfully achieved the synthesis of the fatty sterol with a linker, then linked the target protein to this sterol. Synthesis was started from pregnenolone and achieved by the Grignard reaction with pentenyl magnesium bromide, regioselective photoaddition of thiolacetic acid toward the 25-double bond, esterification of 3-OH with linoleic anhydride, in situ conjunction of the cross-linker (MBS) to the thiol group after selective deprotection from its acetyl ester, and finally by the reaction with protein such as KLH or albumin through this linker.

Neurosteroid analogues. 6. The synthesis and GABAA receptor pharmacology of enantiomers of dehydroepiandrosterone sulfate, pregnenolone sulfate, and (3alpha,5beta)-3-hydroxypregnan-20-one sulfate

The unnatural enantiomers of dehydroepiandrosterone sulfate (1), pregnenolone sulfate (2), and (3alpha,5beta)-3-hydroxypregnan-20-one sulfate (3), compounds 4-6, respectively, were prepared by total steroid synthesis. The enantioselectivity of the compounds as negative modulators of the GABAA receptors present in cultured rat hippocampal neurons was examined using electrophysiological methods. Enantioselectivity was found for the inhibitory actions of the dehydroepiandrosterone enantiomers. The IC50s for compounds 1 and 4 were 11 +/- 1 and 80 +/- 14 microM, respectively. Little, if any, enantioselectivity was found for the other two pairs of steroid sulfate inhibitors. The IC50s for compounds 2 and 5 were 82 +/- 12 and 76 +/- 27 microM, respectively. The IC50s for compounds 3 and 6 were 39 +/- 7 and 46 +/- 2 microM, respectively. The results suggest that the sites of action for the androstane and pregnane series of steroid sulfate blockers of GABA-mediated current are different. The observed enantioselectivity for the actions of dehydroepiandrosterone sulfate indicates that its inhibitory actions are mediated via a chiral recognition site and provides new evidence in support of the earlier hypothesis that there is a binding site for this compound on GABAA receptors. Conversely, the failure to observe enantioselectivity for the actions of pregnenolone sulfate and steroid sulfate 3 indicates that a chiral recognition site for these steroids does not exist on GABAA receptors and suggests that the effects of these compounds on this receptor's function may arise indirectly as a consequence of steroid-induced membrane perturbation.

Identification of intermediates in the conversion of cholesterol to pregnenolone with a reconstituted cytochrome p-450scc system: accumulation of the intermediate modulated by the adrenodoxin level

Dihydroxycholesterol and pregnenolone were clearly detected on HPLC when 22R-hydroxycholesterol was incubated with a reconstituted P450scc system containing equimolar amounts of P450scc and adrenodoxin. The dihydroxycholesterol, which has been accepted to be an intermediate in the conversion of 22R-hydroxycholesterol to pregnenolone, accumulated when adrenodoxin was at a subsaturating level with respect to P450scc. The formation of the intermediate increased with increasing pH in the range of 7.2 to 8.1, and the ratio of the intermediate to the product, pregnenolone, increased with increasing pH. When the binding of P450scc to adrenodoxin was weakened by elevation of the ionic strength, the formation of the intermediate relative to the product increased. The apparent Km for dihydroxycholesterol at a subsaturating level of adrenodoxin was about 7 microM, in contrast to 4 microM at a saturating level of adrenodoxin, implying that the affinity of dihydroxycholesterol is lower at a subsaturating level of adrenodoxin than at a saturating one. These results suggest that a subsaturating level of adrenodoxin weakened the binding of dihydroxycholesterol to P450scc and thus the intermediate, dihydroxycholesterol, was released. An intermediate other than dihydroxycholesterol, obtained when cholesterol was used as the substrate, was identified as 22R-hydroxycholesterol by HPLC and mass spectroscopic analysis. The intermediate obtained when 22R-hydroxycholesterol was used as the substrate was identified as 20R,22R-dihydroxycholesterol by HPLC, mass, and 1H-NMR spectroscopic analyses. These results provide direct evidence that cholesterol is metabolized to pregnenolone by way of 22R-hydroxycholesterol and 20R,22R-dihydroxycholesterol by P45 scc.

Potential tumor- or organ-imaging agents. 29. Radioiodinated esters and amides of 20-hydroxy- and 20-aminopregn-5-en-3 beta-ols

Radioiodinated benzoyl esters and amides of epimeric 20-hydroxy- and 20-aminopregn-5-en-3 beta-ols were synthesized in an effort to find an agent that would be rapidly and selectively taken up by adrenal cortical tissue. Achievement of such a goal would provide a basis for the development of adrenal imaging agents superior to those currently available for clinical use. The iodobenzoyl derivatives were obtained by treating the appropriate epimer with 2-iodobenzoic acid in the presence of dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine. The resulting esters and amides were readily labeled with radioiodine by isotope exchange with sodium iodide-125 in pivalic acid. Tissue distribution studies in female rats revealed that only the esters displayed appreciable adrenal specificity, and the ester having the same configuration at C-20 as cholesterol was significantly better than the corresponding C-20 epimer.

Potential tumor or organ imaging agents--31. Radioiodinated sterol benzoates and carbamates

A series of radioiodinated benzoate and carbamate esters of cholesterol and pregnenolone wherein the acyl moiety served as the carrier for radioiodine was synthesized and evaluated as potential imaging agents for the adrenal cortex. 2,6-Dimethyl-3-iodobenzoyl and N-(4-iodophenyl) carbamoyl groups were chosen as the acyl functionality in an attempt to provide esters resistant to in vivo hydrolysis. Tissue disposition studies in rats revealed that their biodistribution was determined by the attached sterol carrier-the cholesterol esters demonstrated significant uptake at 24 h in the adrenal whereas the corresponding pregnenolone derivatives showed only slight affinity for steroid-secreting tissues at this time.

Potential tumor or organ-imaging agents, 24. Radioiodinated pregnenolone esters

A series of radioiodinated pregnenolone esters was prepared in an effort to find an agent that would be rapidly and selectively taken up by adrenal cortical tissue. Achievement of such a goal would provide the basis for the development of an adrenal imaging agent having several advantages over those agents currently available for clinical use. The radioiodinated esters for this study were readily prepared by treating pregnenolone with the appropriate iodobenzoic acid in the presence of dicyclohexylcarbodiimide (DCC) and 4-dimethylamino-pyridine (DMAP). The resulting esters were readily labeled with radioiodine by isotope exchange with sodium iodide-125 in pivalic acid. Subsequent tissue distribution studies in rats revealed that those esters displaying the most stability towards hydrolysis achieved the highest concentration in adrenal cortical tissue. For example, the 2,3,5-triiodobenzoate (6) showed an adrenal uptake of 23% of administered dose per gram of tissue at 0.5 hours. The achievement of high levels of radioactivity in the adrenal with this agent at early time periods warrants further evaluation of this agent in other animals.

Conversion of 15 alpha-hydroxy-11-oxo-progesterone to 3 beta, 11 alpha, 15 beta-trihydroxy-5-pregnen-20-one

3 beta, 11 alpha, 15 beta-Trihydroxy-5-pregnen-20-one, an intermediate required for the synthesis of the oogoniols, has been prepared from 15 alpha-hydroxy-11-oxoprogesterone in an overall yield of 16%. The three isomers (at C-11, C-15) of the pregnene were also prepared.

Synthesis and reduction of steroid C-20 alkylidene cyanoacetates

The geometry of the condensation products between ethyl cyanoacetate and 20-ketosteroids (5 alpha-pregnane-20-one, 3 beta-hydroxypregn-5-en-20-one and 3 beta-acetoxypregn-5-en-20-one) was established by NMR spectra. Reduction of these steroid C-20 alkylidene cyanoacetates was shown to afford one of the two possible 20-C epimers, which seen to correspond to the 20 beta-methyl configuration.

17 -Hydroperoxypregnenes. IV. A comparative study of the fragmentation by electron impact and high temperature chromatography

The fragmentation of 17α-hydroperoxypregnenolone and 17α-hydroperoxyprogesterone by electron impact and thermolysis is described. It is shown that the fragmentation pattern follows a common pathway for both compounds, determined exclusively by the substituents at ring-D. A new reaction in steroid chemistry, termed deoxygenation, is discovered and its mechanism explained by intramolecular hydrogen abstraction via a six-membered cyclic transition state involving the 20-ketone group.