New CYP17 hydroxylase inhibitors: Synthesis, biological evaluation, QSAR, and molecular docking study of new pregnenolone analogs

Article abstract of DOI:10.1002/ardp.201400255

A new series of pregnenonlone analogs were synthesized and evaluated for their inhibitory activity against cytochrome P450 (CYP17 hydroxylase enzyme). In general, the 5-aryl-1,3,4-thiadiazol-2-yl)-imino-pregnenolone derivatives 11 -15 were more active tha

Full text of DOI:10.1002/ardp.201400255

Arch. Pharm. Chem. Life Sci. 2014, 347, 1–12
1
Full Paper
New CYP17 Hydroxylase Inhibitors: Synthesis, Biological
Evaluation, QSAR, and Molecular Docking Study of
New Pregnenolone Analogs
Najim A. Al-Masoudi1, Dawood S. Ali1, Bahjat Saeed2, Rolf W. Hartmann3, Matthias Engel3,
Sajid Rashid4, and Aamer Saeed5
1
Department of Chemistry, College of Science, University of Basrah, Basrah, Iraq
Department of Chemistry, College of Education, University of Basrah, Basrah, Iraq
Institut für Pharmazeutische und Medizinische Chemie, Universität des Saarlandes, Saarbrücken, Germany
National Center for Bioinformatics, Quaid-i-Azam University, Islamabad, Pakistan
2
3
4
5
Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan
A new series of pregnenonlone analogs were synthesized and evaluated for their inhibitory activity
against cytochrome P450 (CYP17 hydroxylase enzyme). In general, the 5-aryl-1,3,4-thiadiazol-2-yl)-
imino-pregnenolone derivatives 11–15 were more active than the sulfonate 24–31 and the ester 37–41
analogs. Derivative 12 showed optimal activity in this series, with IC50 values of 2.5 mM compared with
the standard abiraterone (IC50 ¼ 0.07 mM). However, the analogs 11 and 25 showed a better selectivity
profile (81.5 and 82.7% inhibition of hydroxylase, respectively), which may be a useful lead in CYP17
inhibition studies. Molecular docking studies demonstrated quite similar binding patterns of all new
pregnenolone derivatives at the active site of CYP17 through hydrogen bonding and hydrophobic
interaction.
Keywords: Anti-HIV activity / CYP17 hydroxylase enzyme / Molecular docking study / Pregnenolone / QSAR
Received: June 27, 2014; Revised: August 19, 2014; Accepted: August 22, 2014
DOI 10.1002/ardp.201400255
Introduction
better inhibitory properties and afforded very potent CYP17
inhibitors [1, 2, 7, 10–15]. Out of these compounds,
ketoconazole 1 (Fig. 1), an imidazole fungicide that has
inhibitory activity toward CYP17 [16, 17], has been used
clinically in high dose for the treatment of advanced PC [4].
However, the fact that it concomitantly inhibits other
steroidal P450 enzymes causing significant side effects [18]
has limited its use. A common approach to the synthesis of
potent steroidal inhibitors of CYP17 has been the design of
substrate-like molecules bearing a heterocycle at the C17
position with privileged heteroatoms (N, S, and O), which can
interact as the sixth ligand with the heme iron of the enzyme.
In addition, computational studies established that a good
inhibitor should possess a sufficiently large hydrophobic core,
comparable to a steroid molecule, and bear electronegative
groups at its external positions [19].
Cytochrome P450’s are enzymes, which catalyze a large
number of biological reactions, for example, hydroxylation,
N-, O-, S-dealkylation, epoxidation, or desamination. Their
substrates include fatty acids, steroids, or prostaglandins. In
addition, a high number of various xenobiotics are metabo-
lized by these enzymes [1]. The enzyme 17a-hydroxylase-
C17,20-lyase (P45017, CYP17, and androgen synthase), a
cytochrome P450 monooxygenase, is the key enzyme for
androgen and corticoid biosynthesis and has become a
valuable target in prostate cancer (PC) treatment [2–7], since
the androgens are potent prostate mitogens [8, 9] and its
elevated levels may be associated with PC risk. Several non-
steroidal compounds have been synthesized, which displayed
In 1996, Njar et al. [20] reported the first steroidal inhibitors
of CYP17 bearing a heterocyclic moiety bound to C17 by a
nitrogen atom, among which the imidazolyl derivative 2 was
found to be the most promising [20–23]. Later, in 2005, the
Correspondence: Dr. Najim A. Al-Masoudi, Department of Chemistry,
College of Science, University of Basrah, Basrah, Iraq.
E-mail: najim.al-masoudi@gmx.de
Fax: þ49 7531 34435
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Arch. Pharm. Chem. Life Sci. 2014, 347, 1–12
Results and discussion
Chemistry
Treatment of pregnenolone 5 with various 2-amino-5-aryl-
2,3,4-thiadiazoles (e.g., 5-phenyl-, 5-(4-methoxyphenyl)-, 5-(4-
bromophenyl)-, 5-(4-chlorophenyl)-, and 5-(4-nitrophenyl)-2-
amino-3,4-thiadiazoles 6–10 in EtOH, using HOAc as a catalyst
afforded, after purification by recrystallization, the imino
derivatives 11–15 in 75, 74, 80, 78, and 75% yield, respectively
(Scheme 1).
The structures of 11–15 were assigned on the basis of their
1H, and 13C NMR spectra, which showed similar patterns of
aliphatic proton and carbon atoms, using the NMR spectrum
of the starting material pregnenolone 5 as a reference.
The multiplet or doublets at the regions d 8.30–7.42 ppm
(J ꢀ 8.9 Hz) were assigned to the aromatic protons. The triplets
at d 5.30 ppm (J ꢀ 2.5 Hz, for the analogs 11–13) and doublet of
doublets (J ¼ 2.2, 3.1 Hz, for the analogs 14 and 15) were
assigned to H-6, respectively, while the broad singlets at the
region d ¼ 4.60–3.60 ppm were attributed to the hydroxyl
group at C-3. The multiplets at the regions d 3.40–3.32 ppm
were assigned to H-3. H-17 appeared as triplets at d 2.57 ppm
(J ꢀ 9.0 Hz), whereas the multiplets at the regions d 2.22–
2.10 ppm were assigned to CH2-4. In the 13C NMR spectra of
11–15, the resonances of C-20 were shifted from d ꢀ 200 ppm
(chemical shift of C-20 of prognenolone 5) into chemical shifts
d 164.6–163.8 ppm, indicative for the formation of the imino
group and attributed to the azomethine carbon atoms. The
signals at d 175.5–169.9 ppm and d 161.8–154.0 ppm were
assigned to the C-50 and C-20 of the thiadiazole ring,
Figure 1. Some inhibitors of CYP 17 hydroxylase-lyase enzyme.
same group reported the synthesis of galeterone 3 and its
D4-3-keto derivative [23–25], where 3 is currently undergoing
phase I/II clinical trials for the treatment of chemotherapy-
naive CRPC [26, 27]. However, patients suffering from CRPC
can clearly benefit from the newly approved drug abiraterone
acetate (Zytiga) 4 [28, 29]. This pregnenolone derivative was
designed as an inhibitor of the enzyme 17a-hydroxylase/
C17,20-lyase (CYP17A1) [30], which catalyzes two key reactions
in steroid hormone biosynthesis.
Herein, we report the synthesis and biological evaluation
of novel 17-pregnenolone-imine derivatives as well as the
3-O-sulfonate and ester analogs at C-3, designed as new
CYP17A1 inhibitors.
Scheme 1. Synthesis of 17-((5-aryl-1,3,4-thiadiazol-2-yl)imino)-5-pregnen-3b-ol derivatives.
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Arch. Pharm. Chem. Life Sci. 2014, 347, 1–12
New Pregnenolone Analogs as CYP17 Hydroxylase Inhibitors
3
respectively. C-3 and C-6 appeared at the regions d 71.7–69.6
and 121.4–120.2 ppm, respectively. The other protons and
carbon atoms of pregnenolone backbone were fully analyzed
(cf. Experimental). Compound 12 has been selected for further
NMR studies, since its HMBC spectrum [31] revealed several
resonances at the regions d 60.1–57.0 and d 56.9–48.2 ppm
were assigned to the pregnane carbon atoms C-14 and C-9,
respectively. The other carbon atoms were fully analyzed
(cf. Experimental).
Our work was modified by synthesis of new pregnenolone
derivatives bearing ester moieties at C-3, aiming for evalua-
tion of their inhibitory activity against the CYP17 hydroxylase
enzyme, which might leading for the treatment of breast
cancer. Thus, treatment of 5 with substituted acyl chlorides
(acyl: 4-chloro-3-nitrobenzoyl- 32, 2,4,5-trifluoro-3-methoxy-
benzoyl- 33, 3,5-dinitrobenzoyl- 34, 3-methoxybenzoyl- 35, and
benzoyl- 36 groups) in pyridine and DMAP afforded, after
purification by column chromatography, the ester analogs
37–41 in 73–62% yield (Scheme 3).
The structures of 37–41 were determined from their NMR
(1H, 13C), which showed a similar pattern of the pregnenolone
scaffold. The structures were deduced as well from the
comparison with those of the analogs 11–15 and 24–31
(cf. Experimental). The aromatic protons resonated as
multiplet, doublets, triplets, or doublet of doublets at the
regions d 9.20–7.06 ppm (J ꢀ 8.8–2.2 Hz). In the 13C NMR
spectra of 37–41, the higher field resonances at d 209.5 ppm
and d 166.0–161.9 ppm were assigned to the carbonyl carbon
2
2
3JC;H and JC;H couplings. A JC;H between H-17 at d 2.58 ppm
3
and C-20 at d 164.1 ppm, as well as a JC;H with C-15 at
d 25.1 ppm were observed.
Next, pregnenolone 5 was treated with various arylsulfonyl
chlorides (aryl: 4-fluorophenyl- 16, 2-trifluoromethoxy- 17, 4-
nitrophenyl- 18, 3-cyanophenyl- 19, 4-bromophenyl- 20, 4-
bromo-2-trifluoromethyphenyl- 21, 3-fluoro-4-methoxyphenyl-
22, and 4-bromo-2,4-difluorophenyl- 23) in the presence of
pyridine and DMAP to give, after purification by column
chromatography, the sulfonate analogs 24–31 in 71–61% yield
(Scheme 2).
1
The structures of 24–31 were assigned from their H NMR
and 13C NMR as well as from the comparison with the spectra
of 11–15. In the 1H NMR spectra of 24–31, broad singlets,
doublets, and multiplet at the regions d 8.15–7.21 ppm were
assigned to the aromatic protons (J ꢀ 9.0 Hz for the doublets).
The aliphatic protons of the pregnenolone scaffold were fully
analyzed as following: H-6 of the pregnane ring appeared as
triplets at the regions d 5.38–5.34 ppm (J ꢀ 2.6 Hz), while H-3 of
the same ring resonated as multiplets at the regions d 4.48–
3.73 ppm. The 13C NMR spectra of 24–31 contained similar
resonance signals of the pregnenolone carbons rings C-1 to C-
21. The higher-field signals between d 219.4 and 209.0 ppm
were assigned to the carbonyl group (C-20), while the
resonances at the regions of d 141.8–137.3 ppm were assigned
to C-5. The chemical shifts at the regions d 82.9–67.0 and 64.0–
63.2 ppm were attributed to C-3 and C-17, respectively. The
–
atoms (C20 O) and CO at C-3, respectively. Resonances at the
–
2
regions d 36.7 and 27.8 ppm were assigned to C-1 and C-2,
respectively, while the signals at the regions d 76.7–74.4,
38.8 and 139.9–138.9 ppm were attributed to C-3 to C-5,
respectively. The other protons and carbon atoms of
pregnenolone backbone and aromatic ring were fully
analyzed (cf. Experimental). Additionally, all the structures
1
of the new synthesized analogs have been identified by H,
13C HSQC NMR spectroscopy [32].
Scheme 2. Synthesis of 5-pregnen-3b-arylsulfonyl-20-one derivatives.
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Scheme 3. Synthesis of 5-pregnen-3b-yl-(substituted-benzoyl)-20-one derivatives.
Bioactivities
In vitro CYP17 hydroxylase enzyme activity
The compounds have been divided into three classes
according to pregnenolone ring mimicking moiety bearing
the residual groups: substituted thiadiazole groups at C-20,
arylsulfonyl, and aryl ester groups at C-3.
The hydroxylase substrate, 17-hydroxypregnenolone is
formed in situ by the cytochrome P450 17a-hydroxylase
enzyme during a 10 min preincubation. At this time point,
almost all pregnenolone substrate has been transformed into
17a-hydroxypregnenolone (>95%). The incubation of an
aliquot is stopped using HCl. At this time point, the
hydroxylase assay is initiated by addition of our test
compounds 11–15, 24–31, and 37–41 in different concen-
trations dissolved in DMSO (final concentration usually
between 0 and 10 mM). The results are presented in Table 1.
The steroidal CYP17A1 inhibitor abiraterone acetate 4 was
used as a reference compound.
When the compound was substituted by hydrogen forming
groups such as oxo or hydroxyl, the resulting compounds
exhibited variation of activity profiles compared to corre-
sponding pregnenolone molecule. The results of Table 1
showed that 11–15 exhibited remarkable inhibition of CYP17
with IC50 values of 4.7, 2.5, 3.4, 3.0, and 3.2 mM, respectively,
whereas blocking of the hydroxyl group at C-2 by the sulfonate
or ester groups (analogs 24–31, 24–31, and 37–41) showed
a significant decrease in the inhibitory activity. Hence, it
is notable that compounds that furnished a hydrogen bond
Table 1. Inhibition of CYP17 hydroxylase enzyme by pregnenolone analogs.
Compd.
IC50 (mM)a)
Inhibition %b)
Compd.
IC50 (mM)a)
Inhibition %b)
11
12
13
14
15
24
25
26
4.7 ꢁ 0.7
2.5 ꢁ 0.0
3.4 ꢁ 0.9
3.0 ꢁ 0.4
3.2 ꢁ 0.6
nd
9.1 ꢁ 1.4
15.2 ꢁ 1.4
11.2
81.5 ꢁ 2.0
78.6 ꢁ 3.0
74.7 ꢁ 4.2
76.3 ꢁ 7.5
11.15
72.0 ꢁ 7.8
82.7 ꢁ 3.3
65.7 ꢁ 6.0
78.7 ꢁ 0.0
28
29
30
31
37
38
39
40
41
8.1 ꢁ 0.4
77.3 ꢁ 4.4
72.1 ꢁ 4.1
67.3 ꢁ 6.9
67.3 ꢁ 6.9
61.9 ꢁ 12.7
5.4 ꢁ 6.5
14.6. ꢁ 8.2
nd
nd
67.3 ꢁ 6.9
nd
nd
nd
nd
12.8 ꢁ 3.3
3.0 ꢁ 2.2
27
6.1 ꢁ 7.4
ABTc)
0.07
a)
Data shown were obtained by performing the tests in duplicate, IC50: the concentration of a inhibitor that is required for 50%
inhibition in vitro.
Hydroxylase enzyme inhibition measured at 50 mM.
b)
c)
ABT, abiraterone; KTZ, ketoconazole; nd, not determined.
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Arch. Pharm. Chem. Life Sci. 2014, 347, 1–12
New Pregnenolone Analogs as CYP17 Hydroxylase Inhibitors
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formation are always more potent and selective, which is
probably caused by some interactions between hydrogen
bond forming groups and certain polar amino acid residues of
the CYP17 enzyme active site [19]. Interestingly, compound 12
having a 4-methoxyphenyl substituent showed a higher
inhibitory activity in comparison for those carrying other
substituents (e.g., H, Br, Cl, and NO2). These data illustrated
that electron-donating substituents (like methoxy group)
would increase the heme iron-complexing imine of the
thiadiazole nitrogen atoms interaction. In general, the
common feature of the analogs 11–15 is a nitrogen atom,
which be able to interact with the heme iron (Feþ2) located in
the active center of CYP enzyme. Such argument is in
agreement with the results reported previously [19, 33].
Although none of the tested compounds is more active than
abiraterone or ketoconazole, compounds 11 and 25 showed a
better selectivity profile (81.5 and 82.7% inhibition of
hydroxylase, respectively) than those of some other reported
steroidal inhibitors [34]. Therefore, these analogs are interest-
ing candidates for further investigation.
standard docking protocol for rigid and flexible ligand
docking consisted of 50 runs, using an initial population of
150 randomly placed individuals, with 2.5 ꢂ 106 energy
evaluations, a maximum number of 27,000 iterations,
mutation rate of 0.02, crossover rate of 0.80, and an elitism
value of 1. Cluster analysis was performed on the docked
results using an RMS tolerance of 1.0 Å. The binding energy
of each cluster is the mean binding energy of all the
conformations present within the cluster. Subsequently,
cluster with the lowest binding energy and higher number of
conformations was selected as the docked pose of that
particular ligand. Table 2 shows the docking parameters,
whereas Table 3 illustrates the binding energies, docking
energies, and inhibition constant values of the pregnenolone
analogs 11–40.
Docking results
Our molecular docking analysis of the new analogs was based
on the human CYP17 homology model [36–38], which
exhibited quite similar binding patterns at the active site
of CYP17. The prospective ligands were ranked according to
the highest binding energy as the best conformers. Thus, the
binding energy score for 11–15 series ranged from ꢃ7 to ꢃ11
(Table 3), while for 24–32 series, it ranged from ꢃ10 to
ꢃ11 kcal/mol, indicating a selectivity of thiadiazole function-
al groups in binding mode alterations. Further, due to the
larger binding pocket of CYP17, bulkier compounds like 11–
15 derivatives easily placed themselves inside the binding
gorge. This also depicts a broad specificity of these compounds
to bind the same position of CYP17.
The best selected dock pose of the analog 11, used as
standard inhibitor, exhibited three hydrogen bond interac-
tions with the triad residue Arg212 with N3thiazdiazole at 3.57 Å,
Phe215 and Gly491 with the OH group at C-3, in addition
to a hydrophobic interaction, and thus participate in p–p
interaction between the phenyl group binding the thiazole
moiety and Phe302 of CYP17 residues (Fig. 2).
Molecular docking study
The fact that molecules 11–15 having structural common
features similar to abiraterone 4 (pregnenolone scaffold) did
show some inhibitory activity against CYP17A1, which
prompted us to study their interaction with the active sites
of the enzyme via the molecular computational studies. In the
docking study, the X-ray crystal structure of human
microsomal cytochrome protein P450 (CYP17; PDBID: 1RUK)
was obtained from Protein Data Bank (http://www.rcsb.
org) [19]. The structure geometries were subsequently
optimized using the Steepest Descent method followed by
Conjugate Gradient in 2000 steps using Accelrys Discovery
Studio (Version2.1, Accelrys Software, http://accelrys.com/).
Optimization was carried out by applying the CHARMm force
field. Automated dockings were performed to locate the
appropriate binding orientations and conformations of these
inhibitors CYP17 protein pocket using AutoDock4.2 tool
according to the specified instructions [35]. In brief, polar
hydrogen atoms and Kollman charges were assigned to the
receptor protein. For small molecules preparation, Gasteiger
partial charges were designated and non-polar hydrogen
atoms were merged. All torsions for ligands were allowed to
rotate during docking procedure. The program AutoGrid was
used to generate the grid maps. Each grid was centered at the
structure of the corresponding receptor. The grid dimensions
were 80 ꢂ 80 ꢂ 80 Å3 with points separated by 0.375 Å. In
general, random starting positions, random orientations,
and torsions were used. The translation, quaternion, and
torsion steps were taken from default values indicated in
AutoDock. The Lamarckian genetic algorithm (LGA) method
was used for minimization using default parameters. The
From the analysis data of Table 1, we conducted that the
analogs 24–31 and 37–41 having bulky sulfonate or acylated
groups at C-3 would not be able to productively engage with
the enzyme, in comparison to the standard abiraterone
acetate 4, the outcome was well correlated with experimental
Table 2. Docking parameters.
Grid parameters
Docking parameters
Spacing
Grid center
0.375 Å
80X Å
80Y Å
80Z Å
Energy evaluations
Iterations
Mutation rate
Crossover rate
Elitism value
RMS tolerance
2.5 ꢂ 106
27,000
0.02
0.80
1
1.0 Å
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Table 3. Binding energies, docking energies, and inhibition constant values of 11–40.
Ligand/properties
11
12
13
14
15
24
25
26
Binding energy (kcal/mol)
Ki (nM)
ꢃ8.94
282.16
ꢃ10.13
ꢃ9.74
ꢃ0.39
ꢃ0.13
1.19
ꢃ7.89
1.66
ꢃ7.95
5.5
ꢃ11.29
5.34
ꢃ12.48
ꢃ12.38
ꢃ0.10
0.34
1.19
0.34
298.5
ꢃ8.37
727.19
ꢃ9.87
ꢃ8.85
ꢃ1.02
ꢃ1.15
1.49
ꢃ9.89
56.74
ꢃ10.04
43.88
ꢃ11.83
ꢃ11.83
0.0
0.02
1.79
0.02
298.5
ꢃ12.10
1.36
Intermolecular energy (kcal/mol)
vdW þ H-bond þ desolv. energy (kcal/mol)
Electrostatic energy (kcal/mol)
Final total internal energy (kcal/mol)
Torsional free energy (kcal/mol)
Unbound system’s energy (kcal/mol)
Temperature (K)
ꢃ9.38
ꢃ9.03
ꢃ0.35
ꢃ0.92
1.49
ꢃ9.14
ꢃ9.05
ꢃ0.09
ꢃ0.7
1.19
ꢃ11.08
ꢃ10.94
ꢃ0.14
ꢃ0.44
1.19
ꢃ13.59
ꢃ12.46
ꢃ1.13
ꢃ0.75
1.49
ꢃ0.13
ꢃ0.92
ꢃ0.7
ꢃ1.15
ꢃ0.44
ꢃ0.75
298.5
298.5
298.5
298.5
298.5
298.5
Ligand/properties
27
28
29
30
31
37
38
39
40
Binding energy (kcal/mol)
Ki (nM)
ꢃ11.01
8.55
ꢃ10.64
15.81
ꢃ7.73
2.15
ꢃ9.92
55.81
ꢃ11.39
ꢃ11.4
0.01
ꢃ10.46
21.19
ꢃ11.66
ꢃ11.6
ꢃ0.03
ꢃ0.49
1.19
ꢃ12.91
346
ꢃ9.41
ꢃ12.31
944.48
ꢃ14.1
ꢃ12.35
ꢃ1.75
ꢃ0.38
1.79
ꢃ9.38
61.12
ꢃ11.33
ꢃ11.36
0.03
125.91
ꢃ10.9
ꢃ10.92
0.02
Intermolecular energy (kcal/mol)
vdW þ Hbond þ desolv energy (kcal/mol)
Electrostatic energy (kcal/mol)
Final total internal energy (kcal/mol)
Torsional free energy (kcal/mol)
Unbound system’s energy (kcal/mol)
Temperature (K)
ꢃ12.2
ꢃ11.84
ꢃ11.74
ꢃ0.14
ꢃ0.66
1.19
ꢃ9.52
ꢃ9.12
ꢃ0.4
ꢃ14.4
ꢃ12.98
ꢃ1.42
ꢃ0.31
1.49
ꢃ12.0
ꢃ0.2
ꢃ0.61
1.19
ꢃ0.38
1.79
ꢃ0.54
ꢃ0.46
ꢃ0.67
1.49
1.49
1.49
ꢃ0.61
ꢃ0.66
ꢃ0.38
ꢃ0.54
298.5
ꢃ0.49
ꢃ0.31
ꢃ0.46
298.5
ꢃ0.38
ꢃ0.67
298.5
298.5
298.5
298.5
298.5
298.5
298.5
results, except few analogs, which showed one hydrogen bond
interaction.
By docking experiment, Ala365, Ala370, and Arg212, were
identified as key residues, located within the binding pocket
of compounds 11–15.
In summary, our study gives an idea about the interaction
between the active site residues and the substrate, which is
explained on the basis of size, hydrophobicity of the binding
pocket, and the position of the substituent (i.e., at C-3 or C-20
of the pregnenolone moiety).
energy model is the most popular mathematical approach to
QSAR. It explains: (i) the physicochemical aspects of drug
transport and distribution from point of application to the
point of effect and (ii) the drug–receptor interaction. Semi-
empirical self-consistent-field molecular orbital (SCF-MO)
method at Austin Model 1 (AM1) [40] level within restricted
Hartree–Kock (RHF) [41] formalism has been considered to
optimize fully the geometry of the pregnenolone molecule
in its ground state. Geometry optimization was carried out
by using
a conjugate gradient method (Polak–Ribiere
algorithm) [42]. The self-consistent-field SCF convergence
was set at 0.001 kcal/mol and the RMS gradient was set to
0.001 kcal/(Å mol) in the calculation. Geometry optimizations
were carried out by PM3 method as implemented in the
Hyperchem 7.5 package. We performed all the calculations
using Hyperchem-7.52 program. In addition, the correlation
analysis and the regression analysis for quantum parameters
were performed by using Minitab program release 11.11. All
calculations were performed on a window XP workstation
in Pentium IV PC.
Quantum-structure–activity relationship (QSAR)
QSAR has been used widely to predict the hazard of untested
chemicals with already tested chemicals by developing
statistical relationships between molecular structure linear
descriptors and biological activity [39]. The Hansch linear free-
Consequently, hydrophobicity is the vital character affect-
ing the biological activity of pregnenolone derivatives, such as
log P (the hydrophobic parameter), dipole moment (m),
polarizability (P), etc.
Geometry parameters
Figure 2. Compound 11 shows three hydrogen bondings:
Arg212 with N3thiazdiazole, Phe212 and Gly491 with OH group at
C-3. In addition, hydrophobic interaction between phenyl group
binding the thiazole moiety and Phe302 of CYP17 residues was
observed.
Geometry parameters are another kind of steric parameters
that have some relations with molecular conformation like
molecular volume (V), molecular surface (S), etc. It is
important to select appropriate molecular descriptors for
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Arch. Pharm. Chem. Life Sci. 2014, 347, 1–12
New Pregnenolone Analogs as CYP17 Hydroxylase Inhibitors
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– F: the overlap function between the inhibitor and
environment electron density.
– S: surface area (A2).
QSAR, such as electronic, hydrophobic, and the geometry [43]
parameters. The selected quantum parameters of the
pregnenolone inhibitors are listed in Table 4.
To obtain the QSAR models, we have correlated the
quantum parameters with each other and the biological
activity (IC50), since some parameters lead to the biological
activities of the inhibitors. Therefore, it is important in QSAR
study to establish the relationship between IC50 and
numerous parameters by regression models [43]. By the
multiple regression analysis, we have selected three models
since r shows an improved values as in Eqs. (1–3).
However, regarding the above interpretation we found the
calculated IC50 of compounds 11–15 are almost in accordance
with their observed IC50 values (Table 5) as inhibitors for the
CYP17 enzyme.
The regression equation is
IC50 ¼ ꢃ61:016869254 ꢂ ðBalaban index JXÞ
ꢃ 4:780334024ðKappa ꢃ 3Þ þ 0:049160570ðKappa ꢃ 1Þ
þ 85:403822251
Two variables:
IC50 ¼ ꢃ1:489ðꢁ1:35ÞMu ꢃ 10:87ðꢁ10:5ÞELUMO
ꢃ 5:137ðꢁ8:81Þ
ð1Þ
ð2Þ
R2 ¼ 0:99999900; adjusted R2 ¼ 0:99999600;
cross validated R2 ¼ 0:99979100
r ¼ 0:959; s ¼ 0:33; F ¼ 11:329
Significant regression ¼ yes; significance-of-regression F-value ¼
3.612021e þ 005; critical SOR F value ð95%Þ ¼ 216:84349500;
computed experimental error ¼ 0:00000000;
replicated points ¼ 0.
Three variables:
ðaÞ IC50 ¼ ꢃ1:616ðꢁ0:68ÞMu þ 2:011ðꢁ2:98ÞEHOMO
ꢃ 13:82ðꢁ6:71ÞELUMO þ 10:16ðꢁ23:0Þ
Experimental
r ¼ 0:999; s ¼ 0:054; F ¼ 306:7
General
ðbÞ IC50 ¼ ꢃ1:466ðꢁ3:48Þ log p ꢃ 0:0776ðꢁ0:083ÞArea
þ 0:0368ðꢁ0:73ÞMass þ 54:72ðꢁ53:4Þ
Melting points were recorded on melting point apparatus
(VEEGO), or a Büchi melting point apparatus B-545 (BÜCHI
Labortechnik AG, Switzerland) and are uncorrected. 1H and 13C
NMR spectra was recorded on a Bruker (Avance III, Germany)
spectrospin-400 and 600 MHz (1H) and 150.91 MHz (13C) spec-
trometers using (CDCl3) containing tetramethylsilane or (DMSO-
d6) as internal standard (chemical shifts in d, ppm). Heteronuclear
assignments were verified by HSQC, 1H, 13C COSY, ROESY, and
HMBC experiments. The IR spectra were measured as KBr disc by
using F.T. IR-8400 (Shimadzu, Japan). Microanalytical data were
obtained with a Vario elemental apparatus (Shimadzu, Japan).
The purity of final products (ꢄ95%) was confirmed by analytical
high performance liquid chromatography (HPLC). HPLC/MS
r ¼ 0:998; s ¼ 0:105; F ¼ 81:0
One variable:
IC50 ¼ ꢃ0:0395ðꢁ0:034ÞArea þ 33:13ðꢁ25:3Þ
r ¼ 0:908; s ¼ 0:397; F ¼ 14:0
ð3Þ
– Values for V (A3) used for calculation of coefficients of the
V1/3 ꢃ log P linear equation.
Table 4. The IC50 and electronic and molecular descriptors calculations used in the QSAR study, the dipole moment m (in Debye),
binding energy (kcal/mol) and heat of formation (kcal/mol).
Compd.
log p
A
V
Ref.
m
Mass (S)
EHOMO
ELUMO
IC50
11
12
13
14
15
26
27
28
29
30
31
7.88
7.62
8.67
8.39
7.83
7.18
5.45
5.53
6.29
7.97
5.81
722.09
770.02
761.62
749.95
762.62
723.18
719.12
712.34
711.14
760.80
673.08
1305.73
1382.06
1370.10
1349.97
1367.72
1322.82
1295.32
1287.25
1294.18
1385.75
1223.85
140.80
147.27
148.42
145.61
148.13
134.05
133.81
132.22
134.10
141.68
126.66
1.383
2.201
3.113
3.371
6.401
7.883
3.057
4.013
5.178
5.18
475.69
505.72
554.59
510.14
520.79
558.63
519.63
499.64
553.53
637.52
ꢃ9.0892
ꢃ1.0765
4.7
2.5
3.4
3.0
3.2
ꢃ8.85739
ꢃ9.340458
ꢃ9.343598
ꢃ9.513567
ꢃ9.519161
ꢃ9.744872
ꢃ9.695738
ꢃ9.485376
ꢃ9.586634
ꢃ9.365929
ꢃ0.99148
ꢃ1.231013
ꢃ1.238171
ꢃ1.628791
ꢃ1.171255
ꢃ1.827834
ꢃ1.260856
ꢃ1.140302
ꢃ1.463645
ꢃ0.7808181
9.1
15.2
11.2
8.1
14.6
67.3
6.353
ß 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

8
N. A. Al-Masoudi et al.
Arch. Pharm. Chem. Life Sci. 2014, 347, 1–12
Table 5. The observed and calculated IC50 of pregnenolone
derivatives.
(m, 2H, H-14 þ H-15b), 1.02 (m, 2H, H-1b þ H-9), 0.97 (s, 3H, Me-19),
13
0.89 (s, 3H, Me-18). C NMR (CDCl3): d 175.5 (C50-thiodiazole),
164.1 (C-20), 161.8 (C20-thiodiazole þ C-OMe), 142.4 (C-5), 128.9,
125.1, 121.1, 115.2 (Carom. þ C-6), 71.7 (C-3), 57.6 (OMe), 56.7 (C-14),
51.0 (C-9); 44.4 (C-13), 43.5 (C-4), 39.7 (C-12), 38.2 (C-1), 37.7 (C-10),
32.7 (Me-21), 32.4 (C-8), 31.6 (C-7), 29.5 (C-2), 25.4 (C-15), 23.5 (C-
16 þ C-17), 21.8 (C-11), 19.8 (Me-19), 13.6 (Me-18). EI: m/z: 505 [M]þ.
Anal. calcd. for C30H39N3OS (505.71): C, 71.25; H, 7.77; N, 8.31.
Found: C, 71.13; H, 7.70; N, 8.22.
Compd.
IC50 obs.
IC50 calcd.
Residual
11
12
13
14
15
4.7
2.5
3.4
3.0
3.2
4.699778
2.4997
3.36496
3.001
ꢃ0.0002
ꢃ0.0003
ꢃ0.035
0.001
3.2002
0.0002
17-((5-(4-Bromophenyl-1,3,4-thiadiazol-2-yl)imino)-5-
pregnen-3b-ol (13)
From 2-amino-5-(4-bromophenyl-1,3,4-thiadiazole (8) (232 mg).
was performed on a MQS electrospray mass spectrometer
(Thermo Fisher) or 70 eV EI and FAB MAT 8200 spectrometers
(Finnigana MAT, USA). UV chamber was used for detection of
spots in TLC. Eluent solvent of TLC were stated, while
development reagent was iodine. Column chromatography was
carried out with silica gel powder (230–400 mesh size) by using
appropriate solvents.
Yield 443 mg (80%), m.p.: 172–174°C, Rf ¼ 0.33. IR (nmax, cmꢃ1):
3256, 3063, 2966, 1636, 1510, 1464, 1290, 1069, 925 cmꢃ1
.
1H NMR (CDCl3): d 7.70 (d, 2H, J ¼ 8.9 Hz, Harom.), 7.66 (d, 2H,
J ¼ 8.9 Hz, Harom.), 5.26 (t, 1H, J ¼ 5.0 Hz, H-6), 4.60 (br s, 1H, OH),
3.32 (m, 1H, H-3), 2.56 (t, 1H, J ¼ 8.9 Hz, H-17), 2.21 (m, 2H, CH2-4),
2.03 (m, 2H, H-12a þ H-16a), 1.98 (s, 3H, Me-21), 1.81 (m, 1H, H-7a),
1.77 (m, 2H, H-1a), 1.62 (m, 1H, H-2a), 1.60–1.54 (m, 4H, H-7b þ H-
11a þ H-15a þ H-16b), 1.46–1.38 (m, 4H, H-2b þ H-8 þ H-11b þ H-
12b), 1.14 (m, 2H, H-14 þ H-15b), 1.03 (m, 2H, H-1b þ H-9), 0.98 (s,
General procedure for the preparation of 17-((5-aryl-1,3,4-
13
3H, Me-19), 0.88 (s, 3H, Me-18). C NMR (CDCl3): d 174.8 (C50-
thiadiazol-2-yl)imino)-5-pregnen-3b-ol derivatives (11–15)
To a solution of pregnen-3b-ol-20-one (5) (316 mg, 1.00 mmol) in
EtOH (20 mL) and glacial acetic acid (1 mL) were added 5-aryl-2-
amino-1,3,4-thiadiazoles 6–10 (1.10 mmol) and the mixture was
heated under reflux for 6–8 h. After cooling, the solution was
poured onto ice-cold water. The solid product was collected by
filtration, and recrystallized from EtOH to give the desired
products.
thiodiazole), 164.6 (C-20), 156.1 (C20-thiodiazole), 141.2 (C-5),
132.0, 130.2, 128.1, 122.6 (Carom.), 120.5 (C-6), 69.6 (C-3), 56.0 (C-14),
49.4 (C-9), 43.2 (C-13), 42.2 (C-4), 38.9 (C-12), 38.0 (C-1), 36.8 (C-10),
31.4 (Me-21), 31.8 (C-8), 31.5 (C-7), 29.2 (C-2), 24.0 (C-15), 22.2
(C-16 þ C-17), 20.6 (C-11), 19.1 (Me-19), 12.9 (Me-18). EI: m/z: 554
[M]þ. Anal. calcd. for C29H36ClN3OS (554.58): C, 62.81; H, 6.54; N,
7.58. Found: C, 62.70; H, 6.39; N, 7.40.
17-((5-Phenyl-1,3,4-thiadiazol-2-yl)imino)-5-pregnen-3b-ol
17-((5-(4-Chlorophenyl-1,3,4-thiadiazol-2-yl)imino)-5-
(11)
pregnen-3b-ol (14)
From 2-amino-5-phenyl-1,3,4-thiadiazole (6) (195 mg). Yield:
357 mg (75%), m.p.: 166–168°C, Rf ¼ 0.61. 1H NMR (CDCl3): d
7.79–7.42 (m, 5H, Harom.), 5.29 (t, 1H, J ¼ 5.1 Hz, H-6), 3.62 (br s, 1H,
OH), 3.38 (m, 1H, H-3), 2.58 (t, 1H, J ¼ 9.1 Hz, H-17), 2.22 (m, 2H,
CH2-4); 2.06 (m, 2H, H-12a þ H-16a), 2.00 (s, 3H, Me-21), 1.84 (m,
1H, H-7a), 1.76 (m, 1H, H-1a), 1.66 (m, 1H, H-2a), 1.61–153 (m, 4H,
H-7b þ H-11a þ H-15a þ H-16b), 1.43–1.35 (m, 4H, H-2b þ H-8 þ H-
11b þ H-12b), 1.18 (m, 2H, H-14 þ H-15b), 1.03 (m, 2H, H-1b þ H-9),
0.98 (s, 3H, Me-19), 0.90 (s, 3H, Me-18). 13C NMR (CDCl3): d 173.7
(C50-thiodiazole), 164.5 (C-20), 158.5 (C20-thiodiazole), 142.4 (C-5),
132.5, 130.4, 129.9, 127.4 (Carom.), 121.4 (C-6), 71.7 (C-3), 57.6 (C-14),
51.1 (C-9), 44.3 (C-13), 43.3 (C-4), 39.5 (C-12), 38.2 (C-1), 37.3 (C-10),
32.7 (Me-21), 32.5 (C-8), 31.5 (C-7), 29.4 (C-2), 25.1 (C-15), 23.4 (C-
16 þ C-17), 21.8 (C-11), 19.8 (Me-19), 13.5 (Me-18). EI: m/z: 475 [M]þ.
Anal. calcd. for C24H37N3OS (475.69): C, 73.22; H, 7.84; N, 8.83.
Found: C, 73.01; H, 7.77; N 8.69.
From 2-amino-5-(4-chlorophenyl-1,3,4-thiadiazole (9) (211 mg).
1
Yield: 398 mg (78%), m.p.: 176–178°C, Rf ¼ 0.36. H NMR (CDCl3):
d 7.77 (d, 2H, J ¼ 8.8 Hz, Harom.), 7.52 (d, 2H, J ¼ 8.8 Hz, Harom.), 5.26
(dd, 1H, J ¼ 3.1, 2.2 Hz, H-6), 4.60 (d, 1H, J ¼ 4.6 Hz, OH), 3.32 (m,
1H, H-3), 2.58 (t, J ¼ 9.1 Hz, H-17), 2.19 (m, 2H, CH2-4), 2.04 (m, 2H,
H-12a þ H-16a), 1.97 (s, 3H, Me-21), 1.89 (m, 1H, H-7a), 1.78 (m, 1H,
H-1a), 1.69 (m, 1H, H-2a), 1.58–1.56 (m, 4H, H-7b þ H-11a þ H-
15a þ H-16b), 1.41–1.37 (m, 4H, H-2b þ H-8 þ H-11b þ H-12b), 1.13
(m, 2H, H-14 þ H-15b), 1.04 (m, 2H, H-1b þ H-9), 0.93 (s, 3H, Me-19),
0.85 (s, 3H, Me-18). 13C NMR CDCl3): d 174.5 (C50-thiodiazole), 164.6
(C-20), 156.1 (C20-thiodiazole), 141.2 (C-5), 133.9, 129.8, 129.1,
127.9 (Carom.), 120.4 (C-6), 69.9 (C-3), 56.0 (C-14), 49.4 (C-9), 43.2
(C-4 þ C-13), 42.2 (C-12), 37.9 (C-1), 36.9 (C-10), 31.4 (s, 3H, Me-21),
31.2 (C-8), 31.0 (C-7), 29.2 (C-2), 24.0 (C-15), 22.2 (C16 þ C-17), 20.6
(C-11), 19.1 (Me-19), 12.9 (Me-18). EI: m/z: 510 [M]þ. Anal. calcd. for
C29H36ClN3OS (510.13): C, 68.28; H, 7.11; N, 8.24. Found: C, 68.09;
H, 7.05; N, 8.12.
17-((5-(4-Methoxyphenyl-1,3,4-thiadiazol-2-yl)imino)-5-
pregnen-3b-ol (12)
17-((5-(4-Nitrophenyl-1,3,4-thiadiazol-2-yl)imino)-5-
pregnen-3b-ol (15)
From 2-amino-5-(4-methoxyphenyl-1,3,4-thiadiazole (7) (228 mg).
Yield: 374 mg (74%), m.p.: 162–164°C, Rf ¼ 0.30. 1H NMR (CDCl3): d
7.71 (d, 2H, J ¼ 8.9 Hz, Harom.), 6.99 (d, 2H, J ¼ 8.9 Hz, Harom.), 5.29
(t, 1H, J ¼ 5.0 Hz, H-6), 3.83 (s, 3H, OMe), 3.62 (br s, 1H, OH), 3.36 (m,
1H, H-3), 2.58 (t, 1H, J ¼ 9.0 Hz, H-17), 2.20 (m, 2H, CH2-4), 2.05 (m,
2H, H-12a þ H-16a), 1.94 (s, 3H, Me-21), 1.83 (m, 1H, H-7a), 1.76 (m,
1H, H-1a), 1.64 (m, 1H, H-2a), 1.60–1.56 (m, 4H, H-7b þ H-11a þ H-
15a þ H-16b), 1.48–1.37 (m, 4H, H-2b þ H-8 þ H-11b þ H-12b), 1.12
From 2-amino-5-(4-nitrophenyl-1,3,4-thiadiazole (10) (244 mg).
Yield: 391 mg (75%), m.p.: 188–190°C, Rf ¼ 0.29. IR (nmax, cmꢃ1):
3405, 3070, 2929, 1682, 1341, 1051, 853. 1H NMR (CDCl3): d 8.30 (d,
2H, J ¼ 9.0 Hz, Harom.), 8.02 (d, 2H, J ¼ 9.0 Hz, Harom.), 5.26 (dd, 1H,
J ¼ 3.3, 2.1 Hz, H-6), 4.60 (d, 1H, J ¼ 4.8 Hz, OH), 3.32 (m, 1H, H-3),
2.58 (t, 1H, J ¼ 9.0 Hz, H-17), 2.10 (m, 2H, CH2-4), 2.06 (m, 2H, H-
12a þ H-16a), 1.91 (m, 3H, Me-21), 1.78 (m, 1H, H-7a), 1.75 (m, 1H,
ß 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Arch. Pharm. Chem. Life Sci. 2014, 347, 1–12
New Pregnenolone Analogs as CYP17 Hydroxylase Inhibitors
9
H-1a), 1.60 (m, 1H, H-2a), 1.56–1.52 (m, 4H, H-7b þ H-11a þ H-
15a þ H-16b), 1.45–1.33 (m, 4H, H-2b þ H-8 þ H-11b þ H-12b), 1.13
(m, 2H, H-14 þ H-15b), 1.04 (m, 2H, H-1b þ H-9), 0.93 (s, 3H, Me-19),
3b-(4-Nitrophenylsulfonyl)-5-pregnen-20-one (26)
From 4-nitrophenylsulfonyl chloride (18) (330 mg). Yield: 341 mg
(68%), m.p.: 84–86°C, Rf ¼ 0.72. 1H NMR (CDCl3): d 8.15, 7.98 (2 ꢂ d,
4H, J ¼ 8.9 Hz, Harom.), 5.38 (t, 1H, J ¼ 2.6 Hz, H-6), 4.10 (m, 1H, H-3),
2.47 (t, 1H, J ¼ 8.9 Hz, H-17), 2.11 (m, 2H, CH2-4), 2.06 (s, 3H, Me-21),
1.97 (m, 2H, H-12a þ H-16a), 1.82 (m, 1H, H-7a), 1.79 (m, 1H, H-1a),
1.64 (m, H, H-2a), 1.57 (m, 4H, H-7b þ H-11a þ H-15a þ H-16b),
1.41–1.34 (m, 4H, H-2b þ H-8 þ H-11b þ H-12b), 1.18 (m, 2H, H-
14 þ H-15b), 0.93 (s, 3H, Me-19), 0.70 (s, 3H, Me-18). 13C NMR
–
13
0.85 (s, 3H, Me-18). C NMR (CDCl3): d 169.9 (C50-thiodiazole),
163.8 (C-20), 154.0 (C20-thiodiazole), 147.3 (C-NO2), 141.2 (C-5),
136.8, 127.0, 124.4 (Carom.), 120.2 (C-6), 69.9 (C-3), 56.0 (C-14), 49.4
(C-9), 43.2 (C-4 þ C-13), 42.2 (C-12), 37.9 (C-1), 36.9 (C-1), 36.1 (C-10),
31.4 (Me-21), 31.2 (C-8), 31.0 (C-7), 29.1 (C-2), 24.0 (C-15), 22.2 (C-
16 þ C-17), 20.6 (C-11), 19.1 (Me-19), 12.9 (Me-18). EI: m/z: 520 [M].
Anal. calcd. for C29H36N4O3S (520.69): C, 66.89; H, 6.97; N, 10.76.
Found: C, 66.72; H, 6.88; N, 10.58.
(CDCl3): d 209.0 (C20 O), 152.0 (Carom-1), 148.1 (Carom-4), 137.3 (C-5),
–
127.2, 123.4, 122.9, 120.8 (Carom. þ C-6), 71.4 (C-3), 63.2 (C-17), 56.8
(C-14), 50.0 (C-9), 44.0 (C-13), 38.8 (C-4 þ C-12), 36.8 (C-10), 33.0 (C-1),
33.3 (C-7), 31.4 (C-8), 30.4 (Me-21), 28.2 (C-2), 24.2 (C-15), 23.6 (C-16),
21.0 (C-11), 20.0 (Me-19), 13.5 (Me-18). EI: m/z: 501 [M]þ. Anal. calcd.
for C27H35NO6S (501.63): C, 64.65; H, 7.03; N, 2.79. Found: C, 64.48;
H, 6.96; N, 2.59.
General procedure for the preparation of pregnenolone
sulfonates (24–31)
To a stirred solution of 5 (316 mg, 1.00 mmol) in abs. pyridine
(20 mL) arylsulfonyl chlorides 16–23 (1.5 mmol) were added. The
reaction mixture was stirred for 6 days at 23°C, and then
quenched by 2 N HCl (10 mL), followed by extraction with ethyl
acetate. The organic layers were washed with saturated NaHCO3,
brine, dried (MgSO4), and filtered. The filtrate was evaporated to
dryness and the residue was purified on a SiO2 column (5 g)
(eluent: n-hexane/ethyl acetate 3:2) to give the desired product.
3b-(3-Cyanophenylsulfonyl)-5-pregnen-20-one (27)
From 3-cyanophenylsulfonyl chloride (19) (302 mg). Yield: 293 mg
1
(61%), m.p.: 108–110°C, Rf ¼ 0.77. H NMR (CDCl3): d 7.40 (d, 2H,
J ¼ 8.9 Hz, Harom.), 7.24 (br s, 1H, Harom.), 5.36 (t, 1H, J ¼ 3.0 Hz, H-6),
4.48 (m, 1H, H-3), 2.52 (t, 1H, J ¼ 9.0 Hz, H-17), 2.18 (m, 2H, CH2-4),
2.11 (s, 3H, Me-21), 2.04 (m, 2H, H-12a þ H-16a), 1.88 (m, 1H, H-7a),
1.80 (m, 1H, H-1a), 1.67 (m, H, H-2a), 1.64 (m, 4H, H-7b þ H-11a þ H-
15a þ H-16b), 1.42 (m, 4H, H-2b þ H-8 þ H-11b þ H-12b), 1.18 (m,
2H, H-14 þ H-15b), 1.14 (m, 2H, H-1b þ H-9), 0.98 (s, 3H, Me-19),
–
3-b-(4-Fluorophenylsulfonyl)-5-pregnen-20-one (24)
From 4-fluorophenylsulfonyl chloride (16) (291 mg). Yield: 299 mg
(63%), m.p.: 118–119°C, Rf ¼ 0.57. IR (nmax, cmꢃ1): 2940, 1728,
0.64 (s, 3H, Me-18). 13C NMR (CDCl3): d 210.0 (C20 O), 141.1 (C
-
–
arom
1
1631, 1508, 1447, 1370, 1256, 1160, 910. H NMR (CDCl3): d 7.91
1 þ C-5), 128.9, 125.2, 123.3, 122.8 (Carom. þ C-6), 114.4 (C-CN), 113.
(CN), 72.4 (C-3), 64.0 (C-17), 57.0 (C-14), 48.2 (C-9), 44.1 (C-13), 40.3
(C-4 þ C-12), 35.2 (C-10), 32.0 (C-1 þ C-7), 30.6 (C-8 þ Me-21), 28.1 (C-
2), 24.5 (C-15), 23.0 (C-16), 21.0 (C-11), 19.3 (Me-19), 13.4 (Me-18). EI:
m/z: 481 [M]þ. Anal. calcd. for C28H35NO4S (481.65): C, 69.82; H,
7.32; N, 2.91. Found: C, 69.68; H, 7.29; N, 2.80.
(dd, 2H, J2 ,3 ¼ J5 ,6 ¼ 9.0 Hz, J2 ,F ¼ J6 ,F ¼ 3.0 Hz, Harom.-20 þ Harom.
-
0
0
0
0
0
0
60), 7.21 (dd, 2H, J3 ,F ¼ J5 ,F ¼ 5.0 Hz, Harom.-30 þ Harom.-50), 5.30 (t,
1H, J ¼ 2.8 Hz, H-6), 4.34 (m, 1H, H-3), 2. 49 (t, J ¼ 9.0 Hz, H-17), 2.15
(m, 2H, CH2-4), 2.09 (m, 2H, H-12a þ H-16a), 2.02 (s, 3H, Me-21),
1.83 (m, 1H, H-7a), 1.80 (m, 1H, H-1a), 1.64 (m, 1H, H-2a),
1.61 (m, 4H, H-7b þ H-11a þ H-15a þ H-16b), 1.41–1.38 (m, 4H,
H-2b þ H-8 þ H-11b þ H-12b), 1.22 (m, 2H, H-14 þ H-15b), 1.14
(m, 2H, H-1b þ H-9), 1.03 (s, 3H, Me-19), 0.70 (s, 3H, M-18). 13C NMR
0
0
3b-(4-Bromophenylsulfonyl)-5-pregnen-20-one (28)
From 4-bromophenylsulfonyl chloride (20) (284 mg). Yield:
342 mg (64%), m.p.: 168–170°C, Rf ¼ 0.54. 1H NMR (CDCl3): d
7.68, 7.51 (2 ꢂ d, 4H, J ¼ 8.8 Hz, Harom.), 5.36 (t, 1H, J ¼ 2.8 Hz, H-6),
4.47 (m, 1H, H-3), 2.53 (t, 1H, J ¼ 8.8 Hz, H-17), 2.19 (m, 2H, CH2-4),
2.12 (s, 3H, Me-21); 2.03 (m, 2H, H-12a þ H-16a), 1.87 (m, 1H, H-7a),
1.83 (m, 1H, H-1a), 1.68 (m, 1H, H-2a), 1.63 (m, 4H, H-7b þ H-
11a þ H-15a þ H-16b), 1.43 (m, 4H, H-2b þ H-8 þ H-11b þ H-12b),
1.20 (m, 2H, H-14 þ H-15b), 1.16 (m, 2H, H-1b þ H-9), 0.93 (s, 3H,
–
–
(CDCl3): d 209.7 (C20 O), 166.8 (d, J ¼ 256 Hz, C-F), 138.9 (C-5),
C,F
134.0, 130.8, 130.6, 123.7 (Carom.), 116.8 (C-6), 82.9 (C-3), 63.8 (C-17),
57.0 (C-14), 50.0 (C-9), 44.1 (C-13), 39.0 (C-4), 37.1 (C-12), 36.6 (C-10),
31.9 (C-1 þ C-7), 30.3 (C-8 þ Me-21), 28.9 (C-2), 24.7 (C-15), 23.1
(C-16), 21.2 (C-11), 19.3 (Me-19), 13.4 (Me-18). EI: m/z: 474 [M]þ. Anal.
calcd. for C27H35FO4S (474.63): C, 68.32; H, 7.43. Found: C, 68.01;
H, 7.31.
Me-19); 0.65 (s, 3H, Me-18). 13C NMR (CDCl3): d 210.0 (C20 O), 141.6
–
–
(C-5), 129.1, 125.4, 123.5, 123.0, 122.4 (Carom. þ C-6), 68.4 (C-3), 64.0
(C-17), 57.3 (C-14), 50.1 (C-9), 43.6 (C-13), 39.2 (C-4 þ C-12), 36.4 (C-
10), 34.0 (C-1), 32.0 (C-7), 30.1 (C-8 þ Me-21), 29.1 (C-2), 24.7 (C-15),
23.2 (C-16), 21.2 (C-11), 19.0 (Me-19), 13.6 (Me-18). EI: m/z: 535 [M]þ.
Anal. calcd. for C27H35BrO4S (535.53): C, 60.55; H, 6.59. Found: C,
60.36; H, 6.38.
3-b-(2-Trifluoromethoxybenzenesulfonyl)-5-pregnen-20-
one (25)
From 2-trifluoromethoxyphenylsulfonyl chloride (17) (389 mg).
1
Yield: 362 mg (67%), m.p.: 88–90°C, Rf ¼ 0.74. H NMR (CDCl3): d
7.24 (m, 5H, Harom.), 5.36 (t, 1H, J ¼ 2.5 Hz, H-6), 3.79 (m, 1H, H-3),
2.57 (t, 1H, J ¼ 8.8 Hz, H-17), 2.19 (m, 2H, CH2-4), 2.10 (s, 3H, Me-21),
2.03 (m, 2H, H-12a þ H-16a), 1.89 (m, 1H, H-7a), 1.84 (m, 1H, H-1a),
1.66 (m, 1H, H-2a), 1.58 (m, 4H, H-7b þ H-11a þ H-15a þ H-16b),
1.47–1.44 (m, 4H, H-2b þ H-8 þ H-11b þ H-12b), 1.19 (m, 2H,
H-14 þ H-15b), 1.12 (m, 2H, H-1b þ H-9), 1.00 (s, 3H, Me-19), 0.61
3b-(4-Bromo-2-trifluoromethylphenylsulfonyl)-5-pregnen-
20-one (29)
(s, 3H, Me-18). 13C NMR (CDCl3): d 209.5 (C20 O), 160.3 (C-OCF ),
From 4-bromo-2-trifluoromethylphenylsulfonyl chloride (21)
(510 mg). Yield: 378 mg (61%), m.p.: 82–84°C, Rf ¼ 0.75. 1H NMR
(CDCl3): d 7.68 (d, 2H, J ¼ 8.9 Hz, Harom.), 7.51 (br s, 1H, Harom.), 5.36
(t, 1H, J ¼ 2.4 Hz, H-6), 4.48 (m, 1H, H-3), 2.56 (t, 1H, J ¼ 9.0 Hz, H-
17), 2.18 (m, 2H, CH2-4), 2.11 (s, 3H, Me-21), 2.02 (m, 2H, H-12a þ H-
16a), 1.86 (m, 1H, H-7a), 1.81 (m, 1H, H-1a), 1.64 (m, 1H, H-2a), 1.61
(m, 4H, H-7b þ H-11a þ H-15a þ H-16b), 1.44 (m, 4H, H-2b þ H-
–
–
3
140.8 (C-5), 132.1, 126.8, 125.1, 123.2, 122.7, 122.2 (Carom. þ C-6),
80.5 (C-3), 63.7 (C-17), 56.9 (C-14), 50.0 (C-9), 43.3 (C-13), 39.1 (C-4),
36.8 (C-10 þ C-12), 33.3 (C-1 þ C-7), 30.5 (C-8 þ Me-21), 28.3 (C-2),
24.5 (C-15), 22.8 (C-16), 21.0 (C-11), 19.3 (Me-19), 13.2 (Me-18).
EI: m/z: 540 [M]þ. Anal. calcd. for C28H35F3O5S (540.63): C, 62.20;
H, 6.53. Found: C, 61.98; H, 6.48.
ß 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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10
N. A. Al-Masoudi et al.
Arch. Pharm. Chem. Life Sci. 2014, 347, 1–12
8 þ H-11b þ H-12b), 1.23 (m, 2H, H-14 þ H-15b), 1.13 (m, 2H,
H-1b þ H-9), 0.88 (s, 3H, Me-19), 0.60 (s, 3H, Me-18). 13C NMR
3b-(4-Chloro-3-nitrobenzoyl)-5-pregnen-20-one (37)
From 4-chloro-3-nitrobenzoyl chloride (32) (330 mg). Yield: 345 mg
1
–
(CDCl3): d 210.0 (C20 O), 168.0 (C-OCF ), 141.0 (C-5), 132.4, 129.1,
(69%), m.p.: 140–142°C, Rf ¼ 0.33. H NMR (CDCl3): d 8.77 (d, 1H,
–
3
127.0, 123.0, 122.4 (Carom. þ C-6), 68.5 (C-3), 64.2 (C-17), 57.1 (C-14),
50.2 (C-9), 43.6 (C-13), 39.4 (C-4), 39.0 (C-12), 36.6 (C-10), 33.6 (C-1),
31.8 (C-7), 30.0 (C-8 þ Me-21), 29.2 (C-2), 24.8 (C-15), 23.3 (C-16), 21.2
(C-11), 19.5 (Me-19), 13.5 (Me-18). EI: m/z: 619 [M]þ. Anal. calcd.
for C28H34BrF3O5S (619.53): C, 54.28; H, 5.53. Found: C, 54.11;
H, 5.46.
0
0
0
0
J2 ,6 ¼ 2.2 Hz, Harom.-2), 8.22 (dd, 2H, J5 ,6 ¼ 8.8 Hz, Harom.-5 þ
Harom.-6), 5.40 (t, 1H, J ¼ 5.5 Hz, H-6), 4.84 (m, 1H, H-3), 2.52 (t, 1H,
J ¼ 9.0 Hz, H-17), 2.20 (m, 2H, CH2-7), 2.11 (s, 3H, Me-21), 2.00 (m,
2H, H-12a þ H-16a), 1.91 (m, 1H, H-7a), 1.80 (m, 1H, H-1a), 1.70 (m,
1H, H-2a), 1.60 (m, 4H, H-7b þ H-11a þ H-15a þ H-16b), 1.51 (m, 4H,
H-2b þ H-8 þ H-11b þ H-12b), 1.26 (m, 2H, H-14 þ H-15b), 1.17 (m,
2H, H-1b þ H-9), 1.06 (s, 3H, Me-19), 0.62 (s, 3H, Me-18). 13C NMR
–
–
–
–
(CDCl3): d 209.5 (C20 O), 163.7 (C O), 158.0 (C-NO ), 138.0 (C-5),
2
3b-(3-Fluoro-4-methoxyphenylsulfonyl)-5-pregnen-20-one
133.2, 127.2 (Carom.), 123.4 (C-6), 75.3 (C-3), 63.7 (C-17), 56.9 (C-14),
50.0 (C-9), 44.0 (C-13), 38.8 (C-4), 38.1 (C-12), 37.0 (C-10), 36.7 (C-1),
31.8 (C-7 þ C-8 þ Me-21), 27.8 (C-2), 24.5 (C-15), 22.9 (C-16), 21.0
(C-11), 19.3 (Me-19), 13.2 (Me-18). EI: m/z: 500 [M]þ. Anal. calcd. for
(30)
From 3-fluoro-4-methoxyphenylsulfonyl chloride (22) (336 mg).
1
Yield: 333 mg (66%), m.p.: 112–114°C, Rf ¼ 0.75. H NMR (CDCl3):
d 7.45 (d, 2H, JH,F ¼ 9.0 Hz, Harom.), 7.03 (d, 2H, J ¼ 8.9 Hz, Harom.
-
C28H34ClNO5 (500.03): C, 67.26; H, 6.85; N, 2.80. Found: C, 67.11;
5 þ Harom.-6), 5.34 (d, 1H, J ¼ 2.8 Hz, H-6), 4.50 (m, 1H, H-3), 3.90
(s, 3H, OMe), 2.54 (t, 1H, J ¼ 9.0 Hz, H-17), 2.19 (m, 2H, CH2-4),
2.10 (s, 3H, Me-21), 2.03 (m, 2H, H-12a þ H-16a), 1.86 (m, 1H, H-7a),
1.82 (m, 1H, H-1a), 1.69 (m, H, H-2a), 1.58 (m, 4H, H-7b þ H-11a þ H-
15a þ H-16b), 1.45 (m, 4H, H-2b þ H-8 þ H-11b þ H-12b), 1.20
(m, 2H, H-14 þ H-15b), 1.10 (m, 2H, H-1b þ H-9), 1.01 (s, 3H, Me-
H, 6.75; N, 2.68.
3b-(2,4,5-Trifluoro-3-methoxybenzoyl)-5-pregnen-20-one
(38)
From 2,4,5-trifluoro-3-methoxybenzoyl chloride (33) (291 mg).
Yield: 294 mg (62%), m.p.: 150–152°C, Rf ¼ 0.66. 1H NMR (CDCl3): d
7.43 (m, 1H, Harom.); 5.40 (t, 1H, J ¼ 5.1 Hz, H-6), 4.83 (m, 1H, H-3),
4.02 (s, 3H, O-Me), 2.54 (t, 1H, J ¼ 9.0 Hz, H-17), 2.45 (m, 2H, CH2-4),
2.20 (m, 2H, CH2-4), 2.11 (s, 3H, Me-21), 2.03 (m, 2H, H-12a þ H-
16a), 1.98 (m, 1H, H-7a), 1.86 (m, H, H-1a), 1.70 (m, 1H, H-2a), 1.62
(m, 4H, H-7b þ H-11a þ H-15a þ H-16b), 1.58–1.44 (m, 4H, H-
2b þ H-8 þ H-11b þ H-12b), 1.23 (m, 2H, H-14 þ H-15b), 1.20 (m,
2H, H-14 þ H-15b), 1.18 (m, 2H, H-1b þ H-9), 1.04 (s, 3H, Me-19),
19), 0.61 (s, 3H, Me-18). 13C NMR (CDCl3): d 209.4 (C20 O), 166.4 (C-
–
–
OMe), 151.1 (C-F, J ¼ 249 Hz), 140.8 (C-5), 137.3, 132.1, 128.9, 126.8,
125.1, 122.7 (Carom. þ C-6), 67.0 (C-3), 63.7 (C-17), 57.1 (C-14), 56.3
(OMe), 50.0 (C-9), 44.0 (C-13), 39.1 (C-4), 38.8 (C-12), 36.4 (C-10), 33.3
(C-1), 31.7 (C-7), 31.5 (C-8 þ Me-21), 29.5 (C-2), 24.4 (C-15), 22.8 (C-
16), 21.0 (C-11), 19.3 (Me-19), 13.2 (Me-18). EI: m/z: 504 [M]þ. Anal.
calcd. for C28H37FO5S (504.65): C, 66.64; H, 7.39. Found: C, 66.49;
H, 7.30.
0.62 (s, 3H, Me-18). 13C NMR (CDCl3): d 209.4 (C20 O), 162.0 (C O),
–
–
–
–
148.6, 145.2, 143.2 (Carom.), 138.9 (C-5), 134.5, 129.4 (Carom.), 123.2
(C-6), 110.0 (Carom.), 75.6 (C-3), 63.7 (C-17 þ OMe), 57.0 (C-14), 51.0
(C-9), 44.1 (C-13), 38.8 (C-4), 38.3 (C-12), 37.2 (C-10), 36.5 (C-1), 32.0
(C-7 þ C-8 þ Me-21), 28.0 (C-2), 24.7 (C-15), 22.9 (C-16), 21.1 (C-11),
19.3 (Me-19), 13.3 (Me-18). EI: m/z: 474 [M]. Anal. calcd. for
3b-(4-Bromo-2,4-difluorophenylsulfonyl)-5-pregnen-20-
one (31)
From 4-bromo-2,4-difluorophenylsulfonyl chloride (23) (437 mg).
Yield: 406 mg (71%), m.p.: 104–106°C, Rf ¼ 0.80. 1H NMR (CDCl3): d
7.68 (m, 1H, Harom.), 7.51 (m, 1H, Harom.), 5.35 (d, 1H, J ¼ 2.7 Hz, H-
6), 4.20 (m, 1H, H-3), 2.50 (t, 1H, J ¼ 9.0 Hz, H-17), 2.20 (m, 2H, CH2-
4), 2.10 (s, 3H, Me-21), 2.02 (m, 2H, H-12a þ H-16a), 1.90 (m, 1H, H-
7a), 1.79 (m, 1H, H-2a), 1.64 (m, 4H, H-7b þ H-11a þ H-15a þ H-16b),
1.45 (m, 4H, H-2b þ H-8 þ H-11b þ H-12b), 1.23 (m, 2H, H-14 þ H-
15b), 1.15 (m, 2H, H-14 þ H-15b), 1.10 (m, 2H, m, 2H, H-1b þ H-9),
0.93 (s, 3H, Me-19), 0.61 (s, 3H, Me-18). 13C NMR (CDCl3): d 219.4
C29H35F3O4 (504.58): C, 69.03; H, 6.99. Found: C, 70.19; H, 6.92.
3b-(3,5-Dinitrobenzoyl)-5-pregnen-20-one (39)
From 3,5-dinitrobenzoyl chloride (34) (345 mg). Yield: 342 mg
1
(67%), m.p.: 206–208°C, Rf ¼ 0.59. H NMR (CDCl3): d 9.20 (t, 2H,
J ¼ 2.2 Hz, Harom.-2 þ Harom.-6), 9.13 (d, 1H, J ¼ 2.2 Hz, Harom.-4),
5.44 (t, 1H, J ¼ 5.0 Hz, H-6), 5.00 (m, 1H, H-3), 2.53 (t, 1H, J ¼ 9.0 Hz,
H-17), 2.20 (m, 2H, CH2-4), 2.13 (s, 3H, Me-21), 2.03 (m, 2H, H-
12a þ H-16a), 2.00 (m, 1H, H-7a), 1.82 (m, 1H, H-1a), 1.70 (m, 1H, H-
2a), 1.64 (m, 4H, H-7b þ H-11a þ H-15a þ H-16b), 1.58–1.45 (m, 4H,
H-2b þ H-8 þ H-11b þ H-12b), 1.23 (m, 2H, H-14 þ H-15b), 1.20 (m,
2H, H-14 þ H-15b), 1.18 (m, 2H, H-1b þ H-9), 1.08 (s, 3H, Me-19),
0
–
–
(C20 O), 163.0 (C5 -F, J
¼ 259 Hz), 155.0 (C20-F, JC20;F ¼ 258 Hz),
C50;F
141.8 (C-5), 126.8, 125.1, 122.7, 122.5, 122.1 (Carom. þ C-6), 117.8 (C-
Br), 68.1 (C-3), 63.9 (C-17), 57.3 (C-14), 50.2 (C-9), 44.1 (C-13), 39.1 (C-
4), 38.6 (C-12), 36.5 (C-10), 32.5 (C-1), 31.8 (C-7), 31.3 (C-8 þ C-21),
29.1 (C-2), 24.5 (C-15), 23.0 (C-16), 21.2 (C-11), 19.5 (Me-19), 13.3 (Me-
18). EI: m/z: 571 [M]þ. Anal. calcd. for C27H33BrF2O4S (571.51): C,
56.74; H, 5.82. Found: C, 56.59; H, 5.77.
0.63 (s, 3H, Me-18). 13C NMR (CDCl3): d 209.4 (C20 O), 161.9 (C O),
–
–
–
–
148.7 (Carom.-3 þ Carom.-5), 139.0 (C-5), 134.7 (Carom.-1), 129.4 (Carom.
-
2 þ Carom.-6), 123.6 (C-6), 122.2 (Carom.-4), 76.7 (C-3), 63.9 (C-17), 56.8
(C-14), 50.0 (C-9), 44.2 (C-13), 38.8 (C-4), 38.4 (C-12), 37.1 (C-10), 36.6
(C-1), 31.6 (C-7 þ C-8 þ Me-21), 27.7 (C-2), 24.5 (C-15), 23.2 (C-16),
21.0 (C-11), 19.4 (Me-19), 13.3 (Me-18). EI: m/z: 510 [M]þ. Anal. calcd.
for C28H34N2O7 (510.58): C, 65.87; H, 6.71; N, 5.49. Found: C, 65.68;
H, 6.62; N, 5.29.
General procedure for the preparation of acylated
pregnenolone derivatives (37–41)
To a stirred solution of 5 (1.00 mmol) in abs. pyridine (20 mL) and
DMAP (mg) were added acyl chlorides 32–36 (1.5 mmol), and
the mixture was heated under reflux for 10 h. The reaction was
quenched by adding 2 N HCl (20 mL) and extracted with ethyl
acetate (20 mL). The mixture organic layer was washed with
saturated NaHCO3 and brine, dried over (MgSO4), filtered, and
evaporated to dryness. The product was purified on SiO2 column
using ethyl acetate/n-hexane as an eluent to give the desired
product.
3b-(3-Methoxybenzoyl)-5-pregnen-20-one (40)
From 3-methoxybenzoyl chloride (35) (278 mg). Yield 320 mg
(71%), m.p.: 156–158°C. Rf ¼ 0.68. 1H NMR (CDCl3): d 7.62 (dd, 1H,
J ¼ 7.7, 2.6 Hz, Harom.-5), 7.60 (d, 1H, J ¼ 7.7 Hz, Harom.-6), 7.54 (d,
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Arch. Pharm. Chem. Life Sci. 2014, 347, 1–12
New Pregnenolone Analogs as CYP17 Hydroxylase Inhibitors
11
1H, J ¼ 2.6 Hz, Harom.-2), 7.06 (dd, 1H, J ¼ 7.7, 2.5 Hz, Harom.-4), 5.40
(t, J ¼ 5.1 Hz, H-6); 4.83 (m, 1H, H-3), 3.83 (s, 3H, OMe), 2.54 (t,
J ¼ 9.1 Hz, H-17), 2.50 (m, 2H, CH2-4), 2.20 (m, 2H, CH2-7), 2.11 (s,
3H, Me-21), 2.01 (m, 2H, H-12a þ H-16a), 1.93 (m, 1H, H-7a), 1.85
(m, 1H, H-1a), 1.70 (m, 1H, H-2a), 1.62 (m, 4H, H-7b þ H-11a þ H-
15a þ H-16b), 1.57–1.44 (m, 4H, H-2b þ H-8 þ H-11b þ H-12b), 1.24
(m, 2H, H-14 þ H-15b), 1.18 (m, 2H, H-1b þ H-9), 1.06 (s, 3H, Me-19),
fresh tube containing 250 mL phosphate buffer and 50 mL 1 N HCl.
Shaking and centrifugation was repeated as described above.
800 mL ethylacetate solution was evaporated to dryness in a fresh
tube and redissolved in 40 mL acetonitrile/water (1:1) for HPLC
analysis.
HPLC methods
0.62 (s, 3H, Me-18). 13C NMR (CDCl3): d 209.5 (C20 O), 165.9 (C O),
–
–
–
–
HPLC separation of the steroids was performed using an Agilent
1100 HPLC system with PDA detector (Böblingen, Germany), a CC
125/3 Nucleodur 100-3 C-18 ec column (Macherey-Nagel, Düren,
0
159.5 (C3 -OMe), 139.7 (C-5), 132.1 (Carom.-1), 129.2 (Carom.-5), 122.5
(C-6), 119.2 (Carom.-4), 114.1 (Carom.-2), 74.5 (C-3), 63.7 (C-17), 56.9
(C-14), 55.4 (O-Me), 49.9 (C-9), 44.0 (C-13), 38.8 (C-4), 38.1 (C-12), 37.0
(C-10), 36.7 (C-1), 31.8 (C-7 þ C-8 þ Me-21), 27.8 (C-2), 24.5 (C-15),
22.8 (C-16), 21.0 (C-11), 19.3 (Me-19), 13.2 (Me-18). EI: m/z: 450 [M].
Anal. calcd. for C29H38O4 (450.61): C, 77.30; H, 8.50. Found: C,
77.14; H, 8.41.
Germany) and
a Berthold radioflow detector LB509 with
scintillator pump (Bad Wildbad, Germany). Quickszint Flow
302 LSC Cocktail (Zinsser Analytic, Frankfurt/Main, Germany) was
used as scintillator fluid. More details are reported in [45].
We thank Basrah University (Iraq) for a scholarship to D. S. Ali. Mr. U.
Haunz and Miss A. Friemel of the Chemistry Department, University
of Konstanz (Germany) are gratefully acknowledged for the 2D-NMR
experiments.
3b-(3-O-Benzoyl)-5-pregnen-20-one (41)
From benzoyl chloride (36) (211 mg). Yield: 307 mg (73%), m.p.:
182–184°C, Rf ¼ 0.67. IR (nmax, cmꢃ1): 2940, 1712, 1450, 1355,
1
1271, 1112, 1026, 945. H NMR (CDCl3): d ¼ 8.04 (m, 5H, Harom.),
5.42 (t, J ¼ 5.0 Hz, H-6), 4.90 (m, 1H, H-3), 2.60 (t, 1H, J ¼ 9.0 Hz, H-
17), 2.50 (m, 2H, CH2-4), 2.20 (m, 2H, CH2-7), 2,13 (s, 3H, Me-21),
2.07 (m, 2H, H-12a þ H-16a), 2.00 (m, 1H, H-7a), 1.80 (m, 1H, H-1a),
1.70 (m, 1H, H-2a), 1.64 (m, 4H, H-7b þ H-11a þ H-15a þ H-16b),
1.56–1.44 (m, 4H, H-2b þ H-8 þ H-11b þ H-12b), 1.25 (m, 2H, H-
14 þ H-15b), 1.22 (m, 2H, H-1b þ H-9), 1.07 (s, 3H, Me-19), 0.64 (s,
The authors have declared no conflict of interest.
References
[1] E. Baston, F. R. Leroux, Recent Patents Anti-Cancer Drug Discov.
2007, 2, 31–58.
3H, Me-18). 13C NMR (CDCl3): d 209.5 (C20 O), 166.0 (C O), 139.9
–
–
–
–
(C-5), 132.7, 130.8, 129.5, 128.3 (Carom.), 122.5 (C-6), 74.4 (C-3), 63.7
(C-17), 56.8 (C-14), 50.1 (C-9), 44.2 (C-13), 38.7 (C-4), 38.2 (C-12), 37.2
(C-10), 36.9 (C-1), 31.7 (C-7 þ C-8 þ Me-21), 28.0 (C-2), 24.7 (C-15),
22.9 (C-16), 21.2 (C-11), 19.5 (Me-19), 13.3 (Me-18). EI: m/z: 420 [M].
Anal. calcd. for C28H36O3 (420.58): C, 79.96; H, 8.63. Found: C,
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