Synthesis, biological evaluation, and molecular modeling studies of methylene imidazole substituted biaryls as inhibitors of human 17α-hydroxylase-17,20-lyase (CYP17)-Part II: Core rigidification and influence of substituents at the methylene bridge

Article abstract of DOI:10.1016/j.bmc.2008.07.011

Thirty-five novel substituted imidazolyl methylene biphenyls have been synthesized as CYP17 inhibitors for the potential treatment of prostate cancer. Their activities have been tested with recombinant human CYP17 expressed in Escherichia coli. Promising compounds were tested for selectivity against CYP11B1, CYP11B2, and hepatic CYP enzymes 3A4, 1A2, 2B6 and 2D6. The core rigidified compounds (30-35) were the most active ones, being much more potent than Ketoconazole and reaching the activity of Abiraterone. However, they were not very selective. Another rather potent and more selective inhibitor (compound 23, IC₅₀ = 345 nM) was further examined in rats regarding plasma testosterone levels and pharmacokinetic properties. Compared to the reference Abiraterone, 23 was more active in vivo, showed a longer plasma half-life (10 h) and a higher bioavailability. Using our CYP17 homology protein model, docking studies with selected compounds were performed to study possible interactions between inhibitors and amino acid residues of the active site.

Full text of DOI:10.1016/j.bmc.2008.07.011

Bioorganic & Medicinal Chemistry 16 (2008) 7715–7727
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis, biological evaluation, and molecular modeling studies
of methylene imidazole substituted biaryls as inhibitors of human
17a-hydroxylase-17,20-lyase (CYP17)—Part II: Core rigidification
and influence of substituents at the methylene bridge
Qingzhong Hu a, Matthias Negri a, Kerstin Jahn-Hoffmann a, , Yan Zhuang a,à, Sureyya Olgen a,§
,
Marc Bartels a, Ursula Müller-Vieira b, Thomas Lauterbach c, Rolf W. Hartmann a,
*
a Pharmaceutical and Medicinal Chemistry, Saarland University, PO Box 151150, D-66041 Saarbrücken, Germany
b Pharmacelsus CRO, Science Park 2, D-66123 Saarbrücken, Germany
c Schwarz Pharma, Alfred-Nobel-Str. 10, D-40789 Monheim, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Thirty-five novel substituted imidazolyl methylene biphenyls have been synthesized as CYP17 inhibitors
for the potential treatment of prostate cancer. Their activities have been tested with recombinant human
CYP17 expressed in Escherichia coli. Promising compounds were tested for selectivity against CYP11B1,
CYP11B2, and hepatic CYP enzymes 3A4, 1A2, 2B6 and 2D6. The core rigidified compounds (30–35) were
the most active ones, being much more potent than Ketoconazole and reaching the activity of Abirater-
one. However, they were not very selective. Another rather potent and more selective inhibitor (com-
pound 23, IC50 = 345 nM) was further examined in rats regarding plasma testosterone levels and
pharmacokinetic properties. Compared to the reference Abiraterone, 23 was more active in vivo, showed
a longer plasma half-life (10 h) and a higher bioavailability. Using our CYP17 homology protein model,
docking studies with selected compounds were performed to study possible interactions between inhib-
itors and amino acid residues of the active site.
Received 5 May 2008
Revised 24 June 2008
Accepted 2 July 2008
Available online 9 July 2008
Keywords:
Prostate cancer
17a-Hydroxylase-17,20-lyase (CYP17)
inhibitors
Pharmacokinetic studies
Testosterone plasma concentrations
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
androgen blockade’ (CAB), which means orchidectomy or treat-
ment with gonadotropin-releasing hormone (GnRH) analogues
It has been illuminated that the growth of up to 80% of prostate
carcinoma, the most common malignancy and cause of death for
male elders, depends on androgen stimulation. Thus, inhibition of
androgen formation or prevention of androgens unfolding activity
will effectively prevent cancer cell proliferation. Currently, the
standard therapy for prostate carcinoma is the so-called ‘combined
(chemical castration) combined with androgen receptor antago-
nists.1 Anti-androgens are used to prevent adrenal androgens,
which are not affected by the former strategies from unfolding
stimulatory effects. However, CAB often leads to resistance, which
can be associated with androgen receptor mutations. The mutated
androgen receptor recognizes antagonists as agonists, and the effi-
ciency of this therapy is whittled away. Total blockage of the
androgen biosynthesis could be a more promising alternative,
which brings CYP17 and its central role in the androgen biosynthe-
sis into focus. CYP17, located in both testicular and adrenal tis-
Abbreviations: CYP, cytochrome P450; CAB, combined androgen blockade;
GnRH, gonadotropin-releasing hormone; CYP17, 17a-hydroxylase-17,20-lyase;
DHEA, dehydroepiandrosterone; DHT, dihydrotestosterone; CDI, 1,1-carbonyl diim-
idazole; TBDMS, tert-butyldimethylsilyl; TBDPS, tert-butyldiphenylsilyl; Boc, tert-
butoxycarbonyl; NMP, N-methylpyrrolidone; ATR, attenuated total reflectance; PE,
petroleum ether; BM, binding mode; GA, genetic algorithm.
* Corresponding author. Tel.: +49 681 302 2424; fax: ++49 681 302 4386.
E-mail address: rwh@mx.uni-saarland.de (R.W. Hartmann).
sues,2 is the key enzyme catalyzing 17
a-hydroxylation and
subsequent C17–C20 bond cleavage of pregnenolone and proges-
terone to form DHEA and androstenedione, which are then con-
verted to testosterone and DHT.3
From Ketoconazole, the first medication that has been used
clinically as CYP17 inhibitor, to Abiraterone, which entered into
phase II clinical trial very recently, several types of CYP17 inhibi-
tors have been synthesized and tested (representative structures
are shown in Chart 1). Almost all the inhibitors, steroidal or non-
steroidal, are mimics of the natural substrates pregnenolone and
URL: http://www.PharmMedChem.de (Rolf W. Hartmann).
Present address: Alnylam Europa AG, Fritz-Harnschuch Str. 9, D-95326 Kulmbach,
Germany.
Present address: Apogee Biotechnology Company, 245 Candlewyck Lane, Her-
shey, PA 17033, USA.
à
§
Present address: University of Ankara, Faculty of Pharmacy, Tandogan, Ankara
06100, Turkey.
0968-0896/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2008.07.011

7716
Q. Hu et al. / Bioorg. Med. Chem. 16 (2008) 7715–7727
N
Cl
O
N
N
O
O
Cl
O
N
C
D
N
S
N
Cl
A
B
N
HO
Cl
HO
N
Ketoconazole
Abiraterone
A
B
HO
OH O
O
HO
N
N
N
O
O
N
NH
O
F
N
O
O
O
CB7645
C
D
E
Chart 1. Structures of typical CYP17 inhibitors.
R5
N
R2
N
R3
N
B(OH)2
N
(i)
N
+
N
N
C
C
N
Br
F3C
F3C
A
A
11
X
R1
R4
Scheme 1. Reagents and conditions: (i) Method C: Pd(PPh3)4, Na2CO3, toluene/
R1 = H, OH, F, alkyl, amino,
amido, CN, CF3
R4 = H, F
EtOH/H2O, reflux, 16 h.
R5 = H, Me
X = NH, CH2
R2 = H, alkyl, phenyl, biphenyl
R3 = H, Me, Et
synthesized by Suzuki coupling (Method C) from the correspond-
ing bromides and boronic acids.14 Subsequently, they were con-
verted to the alcohols by reduction with NaBH4 (Method D) or
Grignard reaction (Method B). The alcohol intermediates were re-
acted with 1,1-carbonyl diimidazole (CDI) (Method A), in a SNt
reaction, to give the racemic mixtures of the desired products,15
which were tested for their inhibitory potencies without further
separation. In the case of some sensitive intermediates, certain
protecting groups were employed and subsequently removed:
tert-butyldimethylsilyl (TBDMS) or tert-butyldiphenylsilyl (TBDPS)
for hydroxy groups and tert-butoxycarbonyl (Boc) for amino
groups. The conversion of the hydroxy compound 26 to the chloro
compound 27 was achieved using SOCl2 (Scheme 5). In some cases,
the carbazole core was constructed by ring closure of the o-nitro
substituted biphenyl refluxed with phosphorous acid triethyl ester
(Scheme 7). The only exception from this strategy was the synthe-
sis of compound 11 (Scheme 1). This compound was simply pre-
Chart 2. General structures of synthesized compounds 1–35.
progesterone. Although lots of steroidal inhibitors are very potent,4
especially Abiraterone,5 the potential drawback of these com-
pounds should not be ignored: the relative short half-life or poor
bioavailability,6 the first pass effect when orally administered7
and the affinity towards steroid receptors, which might result in
side effect no matter acting as agonists or antagonists. All of these
shortcomings indicated the necessity to develop non-steroidal
CYP17 inhibitors. In the past decade, a wide variety of non-steroi-
dal compounds have been described, the most important of these
were tetrahydronaphthalenes (A),8 m-pyridinyl substituted esters
(CB7645 and C),9 1H-imidazol-4-yl substituted alcohols (D and
E),10 and 1-(m-pyridinyl)-3-phenyl substituted heterocycles (B).11
Our group has reported a series of imidazolyl and triazolyl
substituted biphenyls as potent CYP17 inhibitors.12 Recently het-
erocyclic modifications of the core structure were performed with
the more promising biphenyl methylene imidazoles. They have
pared
from
1-(4-bromobenzyl)-1H-imidazole
and
4-
trifluoromethylphenylboronic acid by means of Suzuki coupling
(Method C).
been published recently as part I of this study to further improve
3. Biological results, modeling studies, and discussion
13
biological properties.
In the present paper, modifications such
as the introduction of different substituents at the methylene
bridge as well as the A ring and core rigidifications have been made
leading to compounds 1–35 (general structures shown in Chart 2).
Besides the syntheses and the determination of inhibitory activi-
ties towards human CYP17, the inhibitions of selected compounds
against CYP11B1, CYP11B2, and hepatic CYP enzymes 3A4, 1A2,
2B6, and 2D6 are described. Furthermore, compound 23, as the
most selective inhibitor, was examined for its potency of reducing
plasma testosterone concentration and its pharmacokinetic prop-
erties in rats. Moreover, molecular docking studies with both enan-
tiomers of selected compounds, if existing, were carried out using
our homology model of CYP1713 for getting a closer insight into the
interaction between active site amino acids and the ligands.
CYP17 inhibition of all compounds was evaluated using the
50,000g sediment after homogenation of Escherichia coli expressing
human CYP17 as well as cytochrome P450 reductase.12d The assay
was run with progesterone (25 lM) as substrate and NADPH as
cofactor. Separation of substrate and product was accomplished
by HPLC using UV detection.16a IC50 values are presented in com-
parison to Ketoconazole and Abiraterone in Tables 1–4.
Inheriting from ref. compound 1,12b the influence of different
substituents on the methylene bridge was investigated (Table 1).
From the inhibitory activity values, it becomes apparent that
increasing the length of R2 would largely influence the potency.
The introduction of two-carbon alkyl substituents, like Et (1), and
even more bulky ones like i-Pr (3) and t-Bu (6), increased the po-
tency of the compounds compared to ref. compound
1
2. Chemistry
(IC50 = 910 nM), resulting in inhibitors with IC50 values in a range
from 300 to 450 nM. Interestingly, the further prolongation of
the alkyl chain by another carbon atom led to moderate (2, R2:
n-Pr, IC50 = 580 nM) or low active inhibitors (5, R2: i-Bu,
IC50 = 2100 nM). However, adding another C atom to the alkyl R2
For the synthesis of compounds 1–10 and 12–35 (Schemes
1–7), basically the following strategy was used: the corresponding
ketone or aldehyde intermediates were obtained commercially or

Q. Hu et al. / Bioorg. Med. Chem. 16 (2008) 7715–7727
7717
O
O
B(OH)2
R3
R4
R4
R2
N
O
R2
HO
+
R1
R1
(iv)
(i)
R1
R4
(ii) or (iii)
R3
Br
N
OR
Br
R1
R1
+
(HO)2B
1b, 12b-20b,
23b-25b, 28b-29b
1a-10a, 12a-20a,
23a-25a, 28a-29a
1-10, 12-20,
23-25, 28-29
18: R1 = N(Et)2, R2 = Et, R3 = R4 = H;
19: R1 = morpholino, R2 = Et, R3 = R4 = H;
20: R1 = NHBoc, R2 = Et, R3 = R4 = H;
23: R1 = F, R2 = R4 = Et, R3 = H;
9: R1 = H, R2 = phenyl, R3 = R4 = H;
10: R1 = H, R2 = biphenyl, R3 = R4 = H;
12: R1 = OCF3, R2 = Et, R3 = R4 = H;
13: R1 = SMe, R2 = Et, R3 = R4 = H;
14: R1 = CN, R2 = Et, R3 = R4 =H ;
15: R1 = Me, R2 = R4 = Et, R3 = H;
16: R1 = Et, R2 = R4 = Et, R3 = H;
17: R1 = N(Me)2, R2 = Et, R3 = R4 = H;
1: R1 = H, R2 = Et, R3 = R4 = H;
2: R1 = H, R2 = n-Pr, R3 = R4 = H;
3: R1 = H, R2 = i-Pr, R3 = R4 = H;
4: R1 = H, R2 = n-Bu, R3 = R4 = H;
5: R1 = H, R2 = i-Pr, R3 = R4 = H;
6: R1 = H, R2 = t-Bu, R3 = R4 = H;
7: R1 = H, R2 = cyclohexyl, R3 = R4 = H;
8: R1 = H, R2 = benzyl, R3 = R4 = H;
24: R1 = F, R2 = Me, R3 = R4 = Me;
25: R1 = F, R2 = Et, R3 = R4 = Et;
28: R1 = F, R2 = CH=CH2, R3 = R4 = H;
29: R1 = H, R2 = CH=CH2, R3 = R4 = H;
Scheme 2. Reagents and conditions: (i) Method C: Pd(PPh3)4, Na2CO3, toluene, reflux 6 h; (ii) Method D: 15b–16b, 23b: NaBH4, MeOH; (iii) Method B: 1b, 12b–14b, 17b–20b,
24b–25b, 28b–29b: corresponding Grignard reagent, THF; (iv) Method A: CDI, NMP.
CHO
Br (i)
Br (ii)
TBSO
(iii)
(iv)
(v)
OH
N
N
HO
TBSO
22d
TBSO
HO
22b
22c
22
Scheme 3. Reagents and conditions: (i) TBSCl, Imidazole; (ii) Method C: 4-formylphenylboronic acid, Pd(PPh3)4, Na2CO3, toluene, reflux 6 h; (iii) Method B: EtMgBr, THF; (iv)
Method A: CDI, NMP; (v) TBAF, THF, rt.
N
N
(i)
N
(ii)
N
N
N
O
O
N
H
O
N
H
H2N
21
20
21a
Scheme 4. Reagents: (i) TFA, DCM (ii) AcCl, N(Et)3, DMAP, THF.
O
O
OH
O
Si
O
Si
O
Si
(i)
(ii)
B(OH)2
+
Br
F
F
F
26c
26b
N
N
N
N
N
N
(iii)
(v)
(iv)
O
Si
OH
Cl
F
F
F
26a
26
27
Scheme 5. Reagents and conditions: (i) Method C: Pd(PPh3)4, Na2CO3, toluene, reflux 6 h; (ii) Method D: NaBH4, MeOH; (iii) Method A: CDI, NMP, reflux, 3 h; (iv) TBAF, THF; (v)
SOCl2, DCM.
gave again a very potent compound (4, R2: n-Bu, IC50 = 300 nM).
Furthermore, it could be observed that the activity of the com-
pounds with a bulky group was reduced dramatically as expected,
like benzyl, phenyl (8 and 9 with IC50 values around 800 nM),
cyclohexyl (7, IC50 = 1050 nM), and biphenyl (10, IC50 = 2300 nM).
In the modeling studies, it was observed that all docked com-
pounds showed two binding modes, named BM1 and BM2, which
were identified previously for other biaryl type inhibitors.13,17
These binding modes are different from the proposed substrate
binding mode. 18,19 In BM1 the biaryl plane is oriented almost par-
allel to the I-helix, and principally ligands bearing a R1-substituent
were found in this mode (in Fig. 1, compound 22 is taken as an
example). The substituted A-ring is located next to a polar pocket18
delimitated by Arg109, Lys231, His235, and Asp298, which toler-
ates different substitution patterns. On the other hand, in BM2
the biaryl plane crosses the I-helix, avoiding the interaction with

7718
Q. Hu et al. / Bioorg. Med. Chem. 16 (2008) 7715–7727
R5
N
O
O
HO
(i)
(ii)
R4
R5
R5
R4
R4
N
N
X
X
30c
X
30b, 31a-34a
30a, 31-34
(iv)
(iii)
R5
N
R5
R0
R0
X
30: R0 = OH, R4 = OTBS, R5 = Me, X = CH2;
31: R4 = H, R5 = H, X = CH2;
X
30
32: R4 = H, R5 = Me, X = CH2;
33: R4 = F, R5 = Me, X = CH2;
34: R4 = H, R5 = Me, X = NH;
Scheme 6. Reagents and conditions: (i) Method D: NaBH4, MeOH; (ii) Method A: CDI, NMP, reflux, 3 h; (iii) TBSCl, imidazole; (iv) TBAF, THF.
Table 2
O
Inhibition of CYP17 by compounds 11–23
O
(ii)
(i)
I
R2
N
+
(HO)2B
F
NO2
N
F
NO2
35c
R1
O
11-23
OH
N
N
(iii)
F
(iv)
Compound
R1
R2
CYP17 IC50 (nM)
b
NH
NH
35
NH
F
F
11
12
13
CF3
H
>5000
>5000
3100
>5000
>5000
2000
ꢀ5000
ꢀ5000
2200
1700
>5000
375
35b
35a
OCF3
SMe
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Scheme 7. Reagents and conditions: (i) Method C: Pd(PPh3)4, Na2CO3, toluene,
reflux 6 h; (ii) P(OEt)3, reflux; (iii) Method D: NaBH4, THF, MeOH; (iv) Method A: CDI,
NMP, reflux, 3 h.
14
15
16
CN
Me
Et
17
18
19
20
21
22
N(Me)2
N(Et)2
Morpholino
NHBoc
NHAc
OH
Table 1
Inhibition of CYP17 by compounds 1–10
R2
N
23
F
345
N
KTZa
ABTa
2780
72
a
1-10
KTZ, Ketoconazole; ABT, Abiraterone.
Concentration of inhibitors required to give 50% inhibition. The given values are
b
b
Compound
R2
CYP17 IC50 (nM)
mean values of at least three experiments. The deviations were within 10%.
Ref. 1
1
Me
Et
910
450
Compounds 1, 2, 4, 5, 6, and ref. compound 1 were docked into
our CYP17 model with the aim of explaining the influence of the
different R2 substituents. For all R-enantiomers bearing a short al-
kyl substituent (Et, i-Pr, t-Bu or Me) at the methylene bridge, the
preferred binding mode was BM1; whereas for the corresponding
2
3
4
5
6
7
8
9
n-Pr
i-Pr
n-Bu
i-Bu
t-Bu
Cyclohexyl
Benzyl
Phenyl
580
310
300
2100
460
1050
780
790
S-enantiomers, BM2 seemed to be the most probable. Based on
13,17
the requisites for each binding mode,
both orientations seem
10
KTZa
ABTa
Biphenyl
2300
2780
72
to be possible for compounds 1, 6, and ref. compound 1. On the
other hand, although poses in BM2 could also be observed, the pre-
ferred orientations for compounds 2, 4, and 5 seem to be BM1,
regardless of which enantiomer was considered. This might be
caused by the presence of a longer and bulkier substituent on the
methylene bridge.
a
KTZ, Ketoconazole; ABT, Abiraterone.
Concentration of inhibitors required to give 50% inhibition. The given values are
b
mean values of at least three experiments. The deviations were within 10%.
The results revealed an orientation of the R2 group towards a
tiny hydrophobic pocket, formed by amino acids Ala367-Pro368-
Met369-Leu370-Ile371 (Fig. 2A). Et, i-Pr, and t-Bu substituents
can undergo hydrophobic interactions with this apolar environ-
ment close to the heme without steric clashes due to their reduced
length. However, for compounds 2 (n-Pr) and 5 (i-Bu) steric hin-
drance and hydrophobic repulsion perish the possibility of addi-
tional hydrophobic interactions, thus reducing their inhibitory
potencies. As for compound 4, the results indicate that the n-Bu
the polar pocket. It is a less permissive binding mode, which toler-
ates only planar ligands with an un- or fluorine substituted A-ring
(compound 2 shown in Fig. 1).
Nonetheless, for both binding orientations similar hydrophobic
and
p–p
interactions can be observed,13,17 namely between the
biphenyl core and Phe114 as well as between the biphenyl moiety
and apolar parts of amino acids of the F-helix (Asn202 and Ile206)
and I-helix (Gly301, Ala302, Val304, and Glu305) (Fig. 1).

Q. Hu et al. / Bioorg. Med. Chem. 16 (2008) 7715–7727
7719
Table 3
Inhibition of CYP17 by compounds 23–29
R2
R3
N
N
R1
23-29
R1
R2
R3
CYP17 IC50 (nM)
b
Compound
Ref. 2
23
24
25
26
F
F
F
F
F
F
F
H
Me
Et
Me
Et
(CH2)2OH
(CH2)2Cl
CH@CH2
CH@CH2
H
H
Me
Et
H
H
H
H
1100
345
3800
1300
>5000
756
>5000
1400
2780
72
27
28
29
KTZa
ABTa
a
KTZ, Ketoconazole; ABT, Abiraterone.
Concentration of inhibitors required to give 50% inhibition. The given values are
b
Figure 1. Presentation of the two found binding modes BM1 and BM2, exemplified
mean values of at least three experiments. The deviations were within 10%.
by compounds 22 (magenta, BM1) and
2 (yellow, BM2). Furthermore, heme,
interacting residues and ribbon rendered tertiary structure of the active site are
shown. Figures were generated with Pymol (http://www.pymol.org).
Table 4
Inhibition of CYP17 by compounds 30–35
was found to bind in BM2 as long as the small H-bond accepting
fluorine group can interact with Gln199 and Asn202 (Fig. 2B).
As it is known that fluorine compounds are more stable in vivo
than hydroxy compounds, R1 was sustained to be fluorine, and the
influence of substituents at the methylene bridge was further
investigated (Table 3). Interestingly, the single ethyl group turned
out to be the best, while twin alkyl substituted analogues (24–25)
showed lower inhibitory potency than their single substituted ana-
logues (23, ref. compound 2). This is obviously due to the steric
clashes with amino acids of the I-helix kink and the reduced flex-
ibility of these ligands. Moreover, the similar activity of compound
27 (2-chloroethyl, IC50 = 756 nM) and compound 2 (n-Pr) and the
total loss of activity for the 2-hydroxylethyl analogue (26) demon-
strate the necessity of a hydrophobic side chain on the methylene
bridge.
R5
N
N
X
30-35
R4
R4
R5
X
CYP17 IC50 (nM)
b
Compounds
30
31
32
33
OH
H
H
F
H
F
Me
H
Me
Me
Me
Me
CH2
CH2
CH2
CH2
NH
99
388
112c
168
282
118
2780
72
34
35
NH
KTZa
ABTa
Rigidification of the biphenyl core to form a carbazole or 9H-flu-
orene ring (Table 4) led to the most potent series of compounds
(30–35). The planar conjugated scaffolds apparently contributed
most to the inhibitory potency, probably due to the reduced de-
grees of freedom. Once again, inhibitors furnished with groups
capable of forming hydrogen bonds turned out to be more active,
with the hydroxy substituted 9H-fluorene analogue (30) being
the most potent compound of this study (IC50 = 99 nM, 28-fold
more potent than Ketoconazole). Moreover, the importance of an
alkyl substituent on the spacer has been demonstrated again, as
can be seen from the higher activity of the methyl compound 32
showing an IC50 value of 112 nM (for this compound an IC50 value
of 4 nM is reported23) compared to the corresponding non-substi-
tuted analogue 31 (IC50 = 388 nM).
For the docking studies of selected compounds from Table 4 (30,
32, and 35), similar results were achieved as obtained for the non-
rigidified compounds. Two binding modes, BM1 and BM2, were
identified. The former seemed to be preferred, based on the inter-
nal energies of the docked inhibitors and the visual inspection of
possible interactions, regardless which enantiomer was consid-
ered. The same H-bond interactions were found as described above
(Figs. 1 and 2B). Moreover, the poses were also stabilized by the
electrostatic interactions with carbon chain of Glu305 (Fig. 3).
The inhibition of selected compounds towards hepatic CYP en-
zymes was determined (Table 5), because of their important role in
drug metabolism and drug–drug interaction. Although the com-
a
KTZ, Ketoconazole; ABT, Abiraterone.
Concentration of inhibitors required to give 50% inhibition. The given values are
b
mean values of at least three experiments. The deviations were within 10%.
c
IC50 = 4 nM, reported in Ref. 23.
group can interact not only with amino acids Ile371 and Ala367,
like n-Pr does, but also with Val366, Pro368, and Val382 as addi-
tional contacts. This leads to the stabilization of its orientation,
and makes it a potent inhibitor (Fig. 2A).
It can also be observed that different R1 substituents on the A
ring show a strong influence on the activity of the imidazole
substituted biphenyls. Exhibiting the same ethyl group at the
methylene bridge, the A ring substitution dispersed the inhibitory
potency of the corresponding compounds strongly ranging from no
to strong inhibition (Table 2). It becomes apparent that hydropho-
bic and electronegative groups in R1 led to almost inactive com-
pounds. However, when R1 is a small polar substituent, capable
of H-bond formation, the compounds turned out to be very active
(22, R1 = OH, IC50 = 375 nM; 23, R1 = F, IC50 = 345 nM).
Docking of both enantiomers of ligands 22 and 23 into the ac-
tive site of our CYP17 model revealed that BM1 is preferred for
S-22, R-22, and R-23. There is obviously hydrogen bond formation
between R1 and the polar surrounding of Arg109, Asp298, Lys231,
and His235 (Fig. 2B). However, the S-enantiomer of compound 23

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Q. Hu et al. / Bioorg. Med. Chem. 16 (2008) 7715–7727
Figure 2. A cross-section of the solvent accessible surface of the active site is given with a (A) closer look to the orientation of the R2 methylene linker substituents
(compounds 2 (light blue), 4 (green), 5 (magenta), 6 (violet), 23 (orange), and 27 (yellow)) with their surrounding amino acids and a (B) more in-depth view of the A-ring
substituents (compounds 30 (cyan), S-23 (yellow), R-22 (magenta) and ref. compound 1 (R; green) and interacting residues.
group it bears. However, CYP1A2 inhibition shown by the test com-
pounds was much higher than that of Ketoconazole. Compounds
23 and 27 showed good selectivity towards CYP2B6 and 2D6.
Furthermore, selectivity towards CYP11B1 and CYP11B2—the
most important steroidogenic enzymes being responsible for adre-
nal corticoid biosynthesis—has been determined as another crite-
rion to decide which compound should be tested further in vivo.
CYP11B1 catalyzes 11b-hydroxylation in cortisol biosynthesis,
whereas CYP11B2 is responsible for the final three steps (11b-
hydroxylation, 18-hydroxylation and 18-oxidation) in aldosterone
biosynthesis. Inhibition of these two enzymes could cause hypona-
tremia, hyperkalemia, and a series of recessive disorders, such as
adrenal hyperplasia and hypovolemic shock.20 The most interest-
ing compounds of this series, 23 and 30, were tested at a concen-
tration of 0.2 lM. As compound 23 showed less inhibition on
both enzymes (11B2: 66%; 11B1: 66%, compound 30, 11B1: 96%;
11B2: 98%), it was further tested in rats.
The in vivo evaluation of compound 23, including the ability of
reducing plasma testosterone concentration (Table 6) and the
determination of pharmacokinetic properties (Table 7), was
performed in male Wistar rats after oral application using
Abiraterone as reference compound. The plasma concentrations
of testosterone were determined by ELISA, and plasma drug con-
centrations were measured using LC–MS. Although applied as ace-
tate, only the signals of the free Abiraterone were monitored. It is
obvious that both compounds significantly reduced the plasma
testosterone concentration. It is striking that compound 23, which
was less active in vitro, was much more active in vivo than
Abiraterone at each time point checked. Importantly, after 24 h
compound 23 still showed strong inhibitory activity, while Abira-
terone exhibited at this time point plasma testosterone concentra-
tions six fold higher than that of the untreated control. This
activity profile can be explained by the pharmacokinetic proper-
ties of the compounds. Compound 23 exhibited a plasma half-life
of 10 h, while Abiraterone only showed 1.6 h. The fact that Abira-
terone had to be administrated as acetate prodrug, which is inac-
tive as CYP17 inhibitor, could explain the reduced inhibitory
activity of the steroidal compound. However, application of the
acetate should prolong the plasma half-life having no influence
on the AUC of the parent compound. The superiority of compound
23 becomes apparent by comparing the AUCs of the two com-
pounds, leading to the conclusion that the bioavailability of com-
pound 23 is much better.
Figure 3. Docking complex between CYP17 and compounds 30 (cyan), S-23
(yellow), R-22 (magenta), and ref. compound (R; green). Heme, interacting
residues and ribbon rendered tertiary structure of the active site are shown.
1
Table 5
Inhibition of hepatic CYP enzymes by selected compounds
Compounds
% Inhibitionb
CYP3A4
CYP1A2
CYP2B6
CYP2D6
20
23
25
27
30
32
34
52
88
95
86
89
89
88
75
96
27
nda
97
51
96
93
98
99
nd
8
nd
46
nd
34
nd
nd
nd
nd
11
2
nd
54
nd
32
nd
nd
nd
nd
1
35
KTZa
ABTa
36
7
a
KTZ, Ketoconazole; ABT, Abiraterone; nd, not determined.
Inhibition at a concentration of 1 lM; standard deviations were within < 5%;
b
All the data are the mean values of at least three independent tests.
pounds tested showed inhibition of CYP3A4, it was lower than that
of Ketoconazole. Interestingly, compound 20 showed only little
inhibition (52% at 1 lM), possibly due to the bulky t-Boc amino

Q. Hu et al. / Bioorg. Med. Chem. 16 (2008) 7715–7727
7721
Table 6
Reduction of the plasma testosterone concentrations in rats by compound 23a
b
Compounds
Relative plasma testosterone level (%)
1 h
2 h
4 h
6 h
8 h
24 h
Control
23
143.1 13.3
16.5 5.7d
92.5 43.1d
76.4 13.3
11.7 5.0d
44.0 14.7d
81.4 24.6
13.9 8.0d
43.5 12.4d
109.6 31.7
13.9 7.1d
43.3 12.8c
90.6 22.8
80.6 21.0
d
13.4 6.2
36.7 27.4d
ABTe
35.6 9.7d
476.0 238.6
a
Compound 23 was applied at a dose of 50 mg/kg body weight; Abiraterone was administrated as Abiraterone acetate (56 mg/kg body weight, equivalent to Abiraterone
50 mg/kg body weight). Five to six intact adult male Wistar rats were employed for each treatment group; each sample was tested for three times.
b
The average plasma testosterone concentrations (1.81 ng/mL) at pre-treatment time points (ꢁ1, ꢁ0.5, and 0 h) were set to 100%. The values shown are the relative levels
compared to the pre-treatment value.
c
P < 0.05.
P < 0.01.
ABT, Abiraterone.
d
e
Table 7
Pharmacokinetic properties of compound 23a
b
b
b
b
b
Compound
t1/2z (h)
tmax (h)
Cmax (ng/mL)
AUC0–1 (ng h/mL)
Clint (l/kg/h)
23
10.0
1.6
6.0
2.0
3288
592
70,729
4015
0.7
11.2
Abiraterone
a
Compound 23 was applied at a dose of 50 mg/kg body weight; Abiraterone was administrated as Abiraterone acetate (56 mg/kg body weight, equivalent to Abiraterone
50 mg/kg body weight). Five to six intact adult male Wistar rats were employed for each treatment group; each sample was tested for three times.
b
t1/2z, terminal half-life; tmax, time of maximal concentration; Cmax, maximal concentration; AUC0–1, area under the curve; Clint, intrinsic hepatic clearance.
5.3. Inhibition of CYP11B1 and CYP11B2
4. Conclusion
V79MZh cells expressing human CYP11B1 or CYP11B2 were
incubated with [4-14C]-11-deoxycorticosterone as substrate. The
assay was performed as previously described.16c,d
Herein, we reported the synthesis and evaluation of bioactivity
of a series of substituted and core rigidified biphenyl methylene
imidazoles as CYP17 inhibitors. We found clearer SAR for biphenyl
type CYP17 inhibitors, comparing to previous work,12,13 that alkyl
groups at the methylene bridge, if in suitable length, can strongly
improve the inhibitory potency. Analogues substituted with polar
substituents at the A ring, capable of H-bond formation, always
led to potent inhibitors. Besides, rigidification of the biphenyl core
to form a carbazole or 9H-fluorene ring also significantly elevated
5.4. In vivo study
The in vivo tests were performed with intact adult male Wistar
rats (Harlan Winkelmann, Germany), 5–6 for each treatment
group. These rats were cannulated with silicone tubing via the
right jugular vein. Compound 23 was applied po at 50 mg/kg body
weight, while Abiraterone was administrated as acetate at 56 mg/
kg body weight (equivalent to Abiraterone at 50 mg/kg body
weight). The concentrations of testosterone in the rat plasma were
determined using the Testosterone ELISA (EIA-1559) from DRG
Instruments according to the manufacturer’s instructions. The
plasma drug levels were measured by LC–MS. Non-compartmental
pharmacokinetic analysis of concentration versus time data were
performed for each compound on the mean plasma level using a
validated computer program (PK solution 2 software; Summit Re-
search Services, Montrose, USA). Plasma concentrations below the
limit of detection were assigned a value of zero.
the activity to give a series of CYP17 inhibitors more potent than
12,13
previously reported,
probably due to their planar conjugated
scaffolds. Moreover, one of the best compounds in vitro, compound
23 showed potent activity in vivo, a long plasma half-life and a
high bioavailability.
However, further structure modifications have to be per-
formed with the aim of reducing the CYP1A2 inhibition—the en-
zyme responsible for the metabolism of approximately 10% of
the prescription drugs—before a candidate for the treatment of
prostate cancer can be propagated. Furthermore, because of
being tested as racemic mixtures, it is likely that one enantiomer
of compound 23 would be more potent and selective than the
other.
performed.
A separation of the enantiomers is presently being
5.5. Chemistry
5.5.1. General
5. Experimental
Melting points were determined on a Mettler FP1 melting point
apparatus, and are uncorrected. IR spectra were recorded neat on a
Bruker Vector 33FT-infrared spectrometer. 1H and 13C NMR spectra
were measured on a Bruker DRX-500 (500 MHz). Chemical shifts
are given in parts per million (ppm), and TMS was used as an inter-
nal standard for spectra obtained in CDCl3. All coupling constants
(J) are given in Hertz. ESI (electrospray ionization) mass spectra
were determined on a TSQ quantum (Thermo Electron Corpora-
tion) instrument. Elemental analyses were performed at the
Department of Instrumental Analysis and Bioanalysis, Saarland
University. The purities of the final compounds were controlled
by SurveyorÒ-LC-system. Purities were greater than 98%. Column
5.1. CYP17 preparation and assay
Human CYP17 was expressed in E. coli (coexpressing human
CYP17 and cytochrome P450 reductase) and the assay was per-
formed as previously described.12d,16a
5.2. Inhibition of hepatic CYP enzymes
The recombinantly expressed enzymes from baculovirus-in-
fected insect microsomes (Supersomes) were used and the manu-
facturer’s instructions (www.gentest.com) were followed.

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Q. Hu et al. / Bioorg. Med. Chem. 16 (2008) 7715–7727
chromatography was performed using silica-gel 60 (50–200
l
m),
(CDCl3, 500 MHz) 1.07 (s, 9H, C(CH3)3), 4.92 (s, 1H, CH), 7.08
(s, 1H), 7.24 (s, 1H), 7.32–7.36 (m, 1H), 7.41–7.45 (m,
4H), 7.55–7.57 (m, 4H), 7.72 (s, 1H); MS (ESI): m/z = 291
[M++H].
and reaction progress was determined by TLC analysis on Alu-
gramÒ SIL G/UV254 (Macherey-Nagel). Boronic acids and bromoar-
yls used as starting materials were commercially obtained
(CombiBlocks, Chempur, Aldrich, Acros).
5.5.2.7. 1-(1-Biphenyl-4-yl-cyclohexyl-methyl)-1H-imidazole
5.5.2. Method A: CDI reaction
(7). Synthesized according to Method A using 7a (0.50 g,
To a solution of the corresponding alcohol (1 equiv) in N-meth-
ylpyrrolidone (NMP) or acetonitrile (10 mL/mmol) was added CDI
(5 equiv). Then, the solution was heated to reflux for 4–18 h. After
cooling to ambient temperature, it was diluted with water (30 mL)
and extracted with ethyl acetate (3ꢂ 10 mL). The combined organ-
ic phases were washed with brine, dried over MgSO4, and evapo-
rated under reduced pressure. Then, the desired product was
purified by chromatography on silica gel.
1.87 mmol) and CDI (1.52 g, 9.34 mmol); yield: 0.19 g (32%);
white solid: mp 118–121 °C; Rf = 0.32 (DCM/MeOH, 10:1); dH
(CDCl3, 500 MHz) 0.89–1.03 (m, 2H, cyclohexyl), 1.15–1.28 (m,
3H, cyclohexyl), 1.52–1.60 (m, 2H, cyclohexyl), 1.71–1.77 (m,
3H, cyclohexyl), 2.22–2.23 (m, 1H, cyclohexyl), 4.72 (t,
J = 10.1 Hz, 1H, CH), 7.04 (s, 1H), 7.06 (s, 1H), 7.32–7.37 (m,
3H), 7.43 (dd, J = 7.5, 8.8 Hz, 2H), 7.54–7.57 (m, 4H), 7.63 (s,
1H); MS (ESI): m/z = 317 [M++H].
5.5.2.1. 1-(1-Biphenyl-4-yl-propyl)-1H-imidazole (1). Synthe-
sized according to Method A using 1a (0.50 g, 2.36 mmol) and
CDI (1.91 g, 11.78 mmol); yield: 0.13 g (21%); yellow solid: mp
75–77 °C; Rf = 0.31 (DCM/MeOH, 10:1); dH (CDCl3, 500 MHz) 0.99
(t, J = 7.5 Hz, 3H, CH3), 2.26–2.32 (m, 2H, CH2), 5.09 (t, J = 7.5 Hz,
1H, CH), 6.99 (s, 1H), 7.11 (s, 1H), 7.25 (d, J = 8.4 Hz, 2H), 7.33–
7.37 (m, 1H), 7.42–7.46 (m, 2H), 7.56 (d, J = 8.4 Hz, 2H), 7.58 (d,
J = 8.4 Hz, 2H), 7.69 (s, 1H); MS (ESI): m/z = 263 [M++H].
5.5.2.8. 1-(1-Biphenyl-4-yl-2-phenyl-ethyl)-1H-imidazole (8). Syn-
thesized according to Method A using 8a (0.50 g, 1.82 mmol) and
CDI (1.48 g, 9.11 mmol); yield: 0.14 g (23%); yellow solid: mp
99–101 °C [ref. 98–100 °C21]; Rf = 0.29 (DCM/MeOH, 10:1); dH
(CDCl3, 500 MHz) 3.50 (d, J = 7.5 Hz, 2H, CH2), 5.09 (t, J = 7.5 Hz,
1H, CH), 6.95(s, 1H), 7.01 (d, J = 8.0 Hz, 2H), 7.06 (s, 1H), 7.22–
7.24 (m, 3H), 7.28 (d, J = 8.4 Hz, 2H), 7.35–7.37 (m, 1H), 7.42–
7.45 (m, 2H), 7.48 (s, 1H), 7.56–7.58 (m, 4H); MS (ESI): m/z = 325
[M++H].
5.5.2.2. 1-(1-Biphenyl-4-yl-butyl)-1H-imidazole (2). Synthesized
according to Method A using 2a (0.50 g, 2.21 mmol) and CDI
(1.79 g, 11.05 mmol); yield: 0.16 g (27%); brownish oil; Rf = 0.29
(DCM/MeOH, 10:1); dH (CDCl3, 500 MHz) 0.98 (t, J = 7.5 Hz, 3H,
CH3), 1.31–1.39 (m, 2H, CH2), 2.14–2.28 (m, 2H, CH2), 5.17 (t,
J = 7.5 Hz, 1H, CH), 6.99 (s, 1H), 7.10 (s, 1H), 7.26 (d, J = 8.0 Hz,
1H), 7.34 (t, J = 7.5 Hz, 2H), 7.45 (dd, J = 7.5, 8.4 Hz, 2H), 7.54–
7.57 (m, 4H), 7.66 (s, 1H); MS (ESI): m/z = 277 [M++H].
5.5.2.9. 1-(1-Biphenyl-4-yl-2-phenyl-methyl)-1H-imidazole
(9). Synthesized according to Method
A using 9a (0.50 g,
1.92 mmol) and CDI (1.56 g, 9.60 mmol); yield: 0.07 g (12%);
yellow oil; [ref. mp 142 °C22]; Rf = 0.35 (DCM/MeOH, 10:1); dH
(CDCl3, 500 MHz) 6.57 (s, 1H, CH), 6.89 (s, 1H), 7.13–7.19 (m,
5H), 7.35–7.38 (m, 4H), 7.42–7.47 (m, 3H), 7.56–7.59 (m, 4H);
MS (ESI): m/z = 311 [M++H].
5.5.2.3. 1-(1-Biphenyl-4-yl-2-methyl-propyl)-1H-imidazole
5.5.2.10. 1-(Bis-biphenyl-4-yl-methyl)-1H-imidazole (10). Syn-
thesized according to Method A using 10a (0.50 g, 1.49 mmol)
and CDI (1.21 g, 7.43 mmol); yield: 0.07 g (13%); yellow oil; [ref.
mp 120 °C22]; Rf = 0.37 (DCM/MeOH, 10:1); dH (CDCl3, 500 MHz)
6.95 (s, 1H), 7.16 (s, 1H), 7.21–7.23 (m, 4H), 7.35–7.38 (m, 2H),
7.43–7.47 (m, 4H), 7.55–7.61 (m, 10H); MS (ESI): m/z = 387
[M++H].
(3). Synthesized according to Method
A using 3a (0.50 g,
2.36 mmol) and CDI (1.91 g, 11.78 mmol); yield: 0.20 g (33%);
white solid: mp 124–125 °C; Rf = 0.31 (DCM/MeOH, 10:1); dH
(CDCl3, 500 MHz) 0.95 (t, J = 7.5 Hz, 6H, (CH3)2), 2.56–2.65 (m,
1H, CH(Me)2), 4.67 (d, J = 7.5 Hz, 1H, CH), 7.05 (s, 1H), 7.07 (s,
1H), 7.32–7.38 (m, 3H), 7.42–7.45 (m, 2H), 7.55–7.58 (m, 4H),
7.67 (s, 1H); MS (ESI): m/z = 277 [M++H].
5.5.2.11. 1-(1-(40-(Trifluoromethoxy)biphenyl-4-yl)propyl)-1H-
imidazole (12). Synthesized according to Method A using 12a
(0.50 g, 2.10 mmol) and CDI (2.00 g, 12.40 mmol); yield: 0.16 g
(21%); brownis oil; Rf = 0.51 (DCM/MeOH, 95:5); dH (CDCl3,
500 MHz) 0.99 (t, J = 7.5 Hz, 3H, CH3), 2.26-2.32 (m, 2H, CH2),
5.09 (t, J = 7.5 Hz, 1H, CH), 7.00 (s, 1H), 7.13 (s, 1H), 7.28–7.31
(m, 4H), 7.54–7.59 (m, 4H), 7.66 (s, 1H); dC (CDCl3, 125 MHz)
11.1 (CH3), 28.6 (CH2), 63.0 (CH), 117.6 (CH), 119.5(CF3), 121.2
(CH), 127.0 (Im-C5), 127.5 (CH) 127.6 (CH), 128.4 (CH), 129.5
(Cq), 136.4 (Cq), 139.1 (Cq), 139.7, 139.8 (Cq) 148.8 (Cq); MS (ESI):
m/z = 347 [M++H].
5.5.2.4. 1-(1-Biphenyl-4-yl-pentyl)-1H-imidazole
(4). Synthe-
sized according to Method A using 4a (0.50 g, 2.08 mmol) and
CDI (1.69 g, 10.40 mmol); yield: 0.15 g (25%); brownish oil;
Rf = 0.30 (DCM/MeOH, 10:1); dH (CDCl3, 500 MHz) 0.89 (t,
J = 7.5 Hz, 3H, CH3), 1.28–1.37 (m, 2H, CH2), 1.39–1.43 (m, 2H,
CH2), 2.20–2.26 (m, 2H, CH2), 5.14 (t, J = 7.7 Hz, 1H, CH), 6.99 (s,
1H), 7.12 (s, 1H), 7.26 (d, J = 8.4 Hz, 2H), 7.35 (m, 1H), 7.43 (dd,
J = 7.9, 8.4 Hz, 2H), 7.54–7.57 (m, 4H), 7.68 (s, 1H); MS (ESI): m/
z = 291 [M++H].
5.5.2.5. 1-(1-Biphenyl-4-yl-3-methyl-butyl)-1H-imidazole(5). Syn-
thesized according to Method A using 5a (0.50 g, 2.08 mmol) and CDI
(1.69 g, 10.40 mmol); yield: 0.16 g (27%); brownish oil; Rf = 0.30
(DCM/MeOH, 10:1); dH (CDCl3, 500 MHz) 0.96 (d, J = 7.5 Hz, 6H,
C(CH3)2), 1.46–1.53 (m, 1H, CH(Me)2), 1.99–2.20 (m, 2H, CH2), 5.14 (t,
J = 9.5 Hz, 1H, CH), 6.99 (s, 1H), 7.09 (s, 1H), 7.25 (d, J = 8.0 Hz, 2H),
7.35 (m, 1H), 7.43 (dd, J = 7.9, 8.4 Hz, 2H), 7.54–7.57 (m, 4H), 7.65 (s,
1H); MS (ESI): m/z = 291 [M++H].
5.5.2.12. 1-(1-(40-(Methylsulfanyl)biphenyl-4-yl)propyl)-1H-
imidazole (13). Synthesized according to Method A using 13a
(0.67 g, 2.6 mmol) and CDI (2.00 g, 12.40 mmol); yield: 0.12 g
(15%); beige solid; Rf = 0.44 (DCM/MeOH, 95:5); dH (CDCl3,
500 MHz) 0.96 (t, J = 7.0 Hz, 3H, CH3), 2.24–2.28 (m, 2H, CH2),
2.52 (s, 3H, SCH3), 5.04 (t, J = 7.0 Hz, 1H, CH), 6.97 (s, 1H), 7.10
(s, 1H), 7.23–7.26 (m, 2H), 7.30–7.33 (m, 2H), 7.47–7.50 (m,
2H), 7.52–7.54 (m, 2H), 7.63 (s, 1H); dC (CDCl3, 125 MHz) 11.1
(CH3), 15.8 (SCH3), 28.6 (CH2), 63.0 (CH), 117.7 (Im-C4), 126.9
(CH), 127.0 (CH), 127.2 (CH), 127.4 (CH), 129.5 (Cq), 136.4
(Cq), 137.1 (Cq), 138.0 (Cq), 139.2 (CH), 140.4 (CH); MS (ESI):
m/z = 309 [M++H].
5.5.2.6. 1-(1-Biphenyl-4-yl-2,2-dimethyl-propyl)-1H-imidazole
(6). Synthesized according to Method
A using 6a (0.50 g,
2.08 mmol) and CDI (1.69 g, 10.40 mmol); yield: 0.15 g (25%);
white solid: mp 150-151 °C; Rf = 0.30 (DCM/MeOH, 10:1); dH

Q. Hu et al. / Bioorg. Med. Chem. 16 (2008) 7715–7727
7723
5.5.2.13. 40-(1-(1H-Imidazol-1-yl)propyl)biphenyl-4-carbonitrile
(14). Synthesized according to Method using 14a (0.46 g,
7.08 (s, 1H), 7.21 (d, J = 8.5 Hz, 2H), 7.49 (d, J = 8.8 Hz, 2H),
7.51 (d, J = 8.5 Hz, 2H), 7.61 (s, 1H); dC (CDCl3, 125 MHz) 11.1
(CH3), 28.5 (CH2), 48.9, 62.9 (CH), 66.7, 115.6, 117.6, 126.7,
126.8, 127.6, 129.4, 131.5, 136.3, 138.3, 140.5, 150.6; MS (ESI):
m/z = 348 [M++H].
A
1.93 mmol) and CDI (1.5 g, 9.30 mmol); yield: 0.14 g (25%); brown
oil; Rf = 0.40 (DCM/MeOH, 95:5); dH (CDCl3, 500 MHz) 0.98 (t,
J = 7.0 Hz, 3H, CH3), 2.22–2.30 (m, 2H, CH2), 5.08 (t, J = 7.0 Hz, 1H,
CH), 6.97 (s, 1H), 7.10 (s, 1H), 7.29 (d, J = 8.5 Hz, 2H), 7.56 (d,
J = 8.5 Hz, 2H), 7.61–7.68 (m, 3H), 7.73 (d, J = 8.0 Hz, 2H); dC (CDCl3,
125 MHz) 11.1 (CH3), 28.5 (CH2), 62.9 (CH), 111.2 (C-40), 117.6 (C-N),
118.7 (Im-C4), 127.2 (CH), 127.6 (CH), 129.6 (Cq), 132.6 (CH), 136.3
(Cq), 139.0 (CH), 140.9 (Cq), 144.7 (Cq); MS (ESI): m/z = 288 [M++H].
5.5.2.19. [40-(1H-Imidazol-1-yl-propyl)-biphenyl-4-yl]-carbamic
acid tert-butyl ester (20). Synthesized according to Method A
using 20a (1.23 g, 3.75 mmol) and CDI (0.91 g, 5.63 mmol); yield:
0.33 g (23%); white solid: mp 204–206 °C; Rf = 0.29 (DCM/MeOH,
20:1); dH (CDCl3, 500 MHz) 0.97 (t, J = 7.3 Hz, 3H, CH3), 1.53 (s,
9H, t-Bu), 2.26 (q, J = 7.3, 7.6 Hz, 2H, CH2), 5.04 (t, J = 7.6 Hz, 1H,
CH), 6.57 (s, 1H, CONH), 6.97 (s, 1H), 7.09 (s, 1H), 7.24 (d,
J = 8.2 Hz, 2H), 7.42 (d, J = 8.5 Hz, 2H), 7.51–7.53 (m, 4H), 7.62 (s,
1H); dC (CDCl3, 125 MHz) 11.1 (CH3), 28.3 (t-Bu), 28.6 (CH2), 63.0
(CH), 118.8, 126.9, 127.1, 127.5, 129.5, 137.9, 138.8, 140.5; MS
(ESI): m/z = 378 [M++H].
5.5.2.14. 1-(1-(40-Methylbiphenyl-4-yl)propyl)-1H-imidazole
(15). Synthesized according to Method A using 15a (0.57 g,
2.5 mmol) and CDI (2.0 g, 12.50 mmol); yield: 0.20 g (29%); yel-
low solid: mp 71-72 °C; Rf = 0.26 (EtOAc); dH (CDCl3, 500 MHz)
0.88 (t, J = 7.3 Hz, 3H, CH3), 2.16 (q, J = 7.3 Hz, 2H, CH2), 2.30
(s, 3H, PhCH3), 4.95 (t, J = 7.3 Hz, 1 H, CH), 6.89 (s, 1H), 7.00 (s,
1H), 7.12-7.18 (m, 4H), 7.37 (d, J = 8.2 Hz, 2H), 7.45 (d, J =
8.2 Hz, 2H), 7.54 (s, 1H); dC (CDCl3, 125 MHz) 11.1 (CH3), 21.0
(PhCH3), 28.5 (CH2), 63.0 (CH), 117.6, 126.81, 126.86, 127.3, 129.5,
136.3, 137.3, 138.9, 140.9, 142.1; MS (ESI): m/z = 277 [M++H].
5.5.2.20. 1-[1-(40-Fluoro-biphenyl-4-yl)-propyl]-1H-imidazole
23. Synthesized according to Method
A using 23a (1.23 g,
5.34 mmol) and CDI (4.33 g, 26.70 mmol); yield: 0.52 g (35%);
brown oil; Rf = 0.6 (DCM/MeOH, 95:5); dH (CDCl3, 500 MHz) 0.97
(t, J = 7.3 Hz, 3H, CH3), 2.27 (q, J = 7.3, 7.6 Hz, 2H, CH2), 5.06 (t,
J = 7.6 Hz, 1H, CH), 6.97 (s, 1H), 7.09–7.14 (m, 3H), 7.25 (d,
J = 8.9 Hz, 2H), 7.51–7.53 (m, 4H), 7.62 (s, 1H); dC (CDCl3,
125 MHz) 11.1 (CH3), 28.6 (CH2), 63.0 (CH), 115.6, 115.7, 117.7,
127.0, 127.4, 128.6, 128.7, 129.5, 136.4, 136.5, 139.3, 140.1,
161.6, 163.6; MS (ESI): m/z = 281 [M++H].
5.5.2.15. 1-(1-(40-Ethylbiphenyl-4-yl)propyl)-1H-imidazole
(16). Synthesized according to Method A using 16a (0.64 g,
2.6 mmol) and CDI (2.1 g, 13.12 mmol); yield: 0.14 g (18%);
yellowish oil; Rf = 0.30 (EtOAc); dH (CDCl3, 500 MHz) 0.89 (t,
J = 7.3 Hz, 3H, CH3), 1.20 (t, J = 7.6 Hz, 3H, CH3), 2.18 (quint,
J = 7.3 Hz, 2H, CH2), 2.61 (q, J = 7.6 Hz, 2H, CH2), 4.97 (t,
J = 7.3 Hz, 1H, CH), 6.90 (s, 1H), 7.02 (s, 1H), 7.14-7.21 (m,
4H), 7.41 (d, J = 8.2 Hz, 2H), 7.47 (d, J = 8.5 Hz, 2H), 7.57 (s,
1H); dC (CDCl3, 125 MHz) 10.1 (CH3), 14.5 (CH3), 27.5 (CH2),
27.6 (CH2), 62.1 (CH), 116.7, 125.9, 126.0, 126.4, 127.3, 128.3,
135.3, 136.7, 137.8, 140.0, 142.1; MS (ESI): m/z = 291 [M++H].
5.5.2.21. 1-(2-(40-Fluorobiphenyl-4-yl)propan-2-yl)-1H-imidazole
24. Synthesized according to Method
A using 24a (0.23 g,
1.0 mmol) and CDI (0.36 g, 2.20 mmol); yield: 0.05 g (19%);
Rf = 0.27 (DCM/MeOH, 95:5); dH (CDCl3, 500 MHz) 1.94 (s, 6H,
CH3), 6.94–6.96 (m, 1H), 7.10–7.15 ( m, 5H), 7.47–7.36 (m, 4H),
7.67–7.69 (m, 1H); dC (CDCl3, 125 MHz) 31.5 (CH3), 60.3 (CH),
116.1, 117.0, 125.2, 127.3, 129.2, 132.6, 139.4, 145.4, 163.7; MS
(ESI): m/z = 281 [M++H].
5.5.2.16. [40-(1H-Imidazol-1-yl-propyl)-biphenyl-4-yl]-dimethyl-
amine (17). Synthesized according to Method A using 17a (0.59 g,
2.31 mmol) and CDI (0.56 g, 3.47 mmol); yield: 0.18 g (25%); white
solid: mp 117–119 °C; Rf = 0.33 (DCM/MeOH, 20:1); dH (CDCl3,
500 MHz) 0.95 (t, J = 7.3 Hz, 3 H, CH3), 2.24 (q, J = 7.3, 7.6 Hz, 2H,
CH2), 2.99 (s, 6H, N-CH3), 5.01 (t, J = 7.6 Hz, 1H, CH), 6.78 (d,
J = 9.1 Hz, 2H), 6.97 (s, 1H), 7.09 (s, 1H), 7.20 (d, J = 8.5 Hz, 2H),
7.47 (d, J = 8.8 Hz, 2H), 7.51 (d, J = 8.2 Hz, 2H), 7.62 (s, 1H); dC (CDCl3,
125 MHz) 11.1 (CH3), 28. 6 (CH2), 40.4 (N-CH3), 63.0 (CH), 112.6,
117.6, 126.5, 126.8, 127.6, 129.4, 136.4, 137.7, 141.0, 150.1; MS
(ESI): m/z = 306 [M++H].
5.5.2.22. 1-(3-(40-Fluorobiphenyl-4-yl)pentan-3-yl)-1H-imidazole
(25). Synthesized according to Method
A using 25a (0.26 g,
1.00 mmol) and CDI (0.36 g, 2.20 mmol); yield: 0.13 g (43%);
Rf = 0.33 (DCM/MeOH, 95:5); dH (CDCl3, 500 MHz) 0.75 (s, 6H,
CH3), 2.26–2.30 (q, 4H, CH2), 6.84–6.86 (m, 1H), 7.08–7.09 (m, 1H),
7.10–7.13 (m, 2H), 7.17–7.20 (m, 2H), 7.48–7.55 (m, 4H), 7.62–
7.63 (m, 1H); dC (CDCl3, 125 MHz) 8.3 (CH3), 30.5 (CH2), 66.1 (CH),
116.3, 119.7, 127.6, 129.9, 136.2, 139.1, 142.8; MS (ESI): m/z = 309
[M++H].
5.5.2.17. Diethyl-[40-(1H-imidazol-1-yl-propyl)-biphenyl-4-yl]-
amine (18). Synthesized according to Method A using 18a (0.70 g,
2.47 mmol) and CDI (0.61 g, 3.70 mmol); yield: 0.16 g (19%); white
solid: mp 109–111 °C; Rf = 0.33 (DCM/MeOH, 20:1); dH (CDCl3,
500 MHz) 0.95 (t, J = 7.3 Hz, 3H, CH3), 1.19 (t, J = 6.9 Hz, 6H, N-
CH3), 2.24 (q, J = 7.3, 7.6 Hz, 2H, CH2), 3.39 (q, J = 6.9 Hz, 4H, N-
CH2), 5.01 (t, J = 7.6 Hz, 1H, CH), 6.73 (d, J = 9.1 Hz, 2H), 6.97 (s,
1H), 7.09 (s, 1H), 7.19 (d, J = 8.5 Hz, 2H), 7.45 (d, J = 8.8 Hz, 2H),
7.50 (d, J = 8.2 Hz, 2H), 7.62 (s, 1H); dC (CDCl3, 125 MHz) 11.1
(CH3), 12.6 (N-CH3), 28.6 (CH2), 44.3 (N-CH2), 63.0 (CH), 111.8,
117.6, 126.3, 126.8, 127.7, 129.4, 136.4, 137.5, 141.1, 147.3; MS
(ESI): m/z = 334 [M++H].
5.5.2.23. 1-(1-(40-Fluorobiphenyl-4-yl)allyl)-1H-imidazole (28). Syn-
thesized according to Method A using 28a (1.14 g, 5.00 mmol) and CDI
(1.80 g, 10.10 mmol); yield: 0.57 g (41%); Rf = 0.27 (DCM/MeOH, 95:5);
dH (CDCl3, 500 MHz) 4.73–4.74 (m, 2H, CH2), 6.30–6.35 (m, 1H, CH),
6.54–6.57 (m, 1H, CH), 6.98 (s, 1H), 7.10–7.12 (m, 3H), 7.42–7.44 (m,
2H), 7.50–7. 56 (m, 5H); dC (CDCl3, 125 MHz) 49.3 (CH), 116.5, 124.9,
127.4, 128.6, 130.8, 133.2, 135.2, 137.0, 140.3, 161.7; MS (ESI): m/
z = 279 [M++H].
5.5.2.24. 1-(1-(Biphenyl-4-yl)allyl)-1H-imidazole (29). Synthe-
sized according to Method A using 29a (0.30 g, 1.00 mmol) and
CDI (0.36 g, 2.20 mmol); yield: 0.09 g (32%); Rf = 0.21 (DCM/
MeOH, 95:5); dH (CDCl3, 500 MHz) 4.73–4.75 (m, 2H, CH2),
6.30–6.35 (m, 1H, CH), 6.56–6.57 (m, 1H, CH), 6.98 (s, 1H),
7.12–7.13 (m, 1H), 7.34–7.37 (m, 1H), 7.43–7.46 (m, 4H), 7.56–
7.60 (m, 5H); dC (CDCl3, 125 MHz) 49.3 (CH), 119.4 (@CH2),
123.8, 127.0, 129.4, 133.2, 134.5, 137.7, 140.9; MS (ESI): m/
z = 297 [M++H].
5.5.2.18. 4-[40-(1H-Imidazol-1-yl-propyl)-biphenyl-4-yl]-
morpholine (19). Synthesized according to Method A using 19a
(0.70 g, 2.37 mmol) and CDI (0.58 g, 3.55 mmol); yield: 0.27 g
(33%); white solid: mp 119–121 °C; Rf = 0.17 (DCM/MeOH,
20:1); dH (CDCl3, 500 MHz) 0.95 (t, J = 7.3 Hz, 3H, CH3), 2.24 (q,
J = 7.3, 7.6 Hz, 2H, CH2), 3.20 (t, J = 4.7 Hz, 4H), 3.86 (t,
J = 4.7 Hz, 4H), 5.02 (t, J = 7.6 Hz, 1H, CH), 6.92–6.95 (m, 3H),

7724
Q. Hu et al. / Bioorg. Med. Chem. 16 (2008) 7715–7727
5.5.2.25. 1-((9H-Fluoren-2-yl)methyl)-1H-imidazole (31). Syn-
thesized according to Method A using 31a (0.32 g, 1.63 mmol)
5.5.3. Method B: Grignard reaction
Under exclusion of air and moisture a 1.0 M Grignard reagent
(1.2 equiv) solution in THF was added dropwise to a solution of
the aldehyde or ketone (1 equiv) in THF (12 mL/mmol). The mix-
ture was stirred at room temperature overnight. Subsequently
ethyl acetate (10 mL) and water (10 mL) were added, and the
organic phase was separated. The organic phase was extracted
with water and brine, dried over Na2SO4 and evaporated under
reduced pressure. The crude products were purified by flash
chromatography on silica gel.
and CDI (0.53 g, 3.26 mmol); yield: 0.16
g (40%); Rf = 0.31
(MeOH/EtOAc, 5:95); colorless solid: mp 183–185 °C; dH (CDCl3,
500 MHz) 3.87 (s, 2H, CH2), 5.18 (s, 2H), 6.94 (br s, 1H), 7.11 (br
s, 1H), 7.19 (d, J = 8.5 Hz, 1H), 7.30–7.33 (m, 2H), 7.38 (dd, J = 7.3,
7.6 Hz, 1H), 7.54 (d, J = 7.6 Hz, 1H), 7.59 (br s, 1H), 7.75 (d,
J = 7.9 Hz, 1H), 7.77 (d, J = 7.6 Hz, 1H); dC (CDCl3, 125 MHz) 36.8
(CH2), 51.0 (CH2), 119.3 (CH), 120.0 (CH), 120.2 (CH), 124.0 (CH),
125.1 (CH), 126.1 (CH), 126.8 (CH), 127.1 (CH), 129.7 (CH), 134.4
(Cq), 137.4 (CH), 140.9 (Cq), 141.9 (Cq), 143.3 (Cq), 144.1 (Cq); MS
(ESI): m/z = 247 [M++H].
5.5.3.1. 1-Biphenyl-4-yl-3-methyl-butan-1-ol (5a). Synthesized
according to Method B using Biphenyl-4-carbaldehyde (1.00 g,
5.48 mmol) and a 1.0 M iso-butylmagnesiumbromide solution
in THF (7.13 mL, 7.13 mmol); yield: 0.96 g (73%); Rf = 0.28 (PE/
EtOAc, 5:1); dH (CDCl3, 500 MHz) 0.97 (d, J = 4.9 Hz, 6H, CH3),
1.51–1.58 (m, 1H, CH), 1.72 (s, br, 1H, OH), 1.75–1.81 (m, 2H,
CH2), 4.79 (t, J = 2.7 Hz, 1H, CH), 7.33 (t, J = 7.5 Hz, 1H), 7.43 (d,
J = 8.4 Hz, 4H), 7.57 (d, J = 8.4 Hz, 4H); MS (ESI): m/z = 241
[M++H].
5.5.2.26. 1-((9H-Fluoren-2-yl)ethyl)-1H-imidazole (32). Synthe-
sized according to Method A using 32a (1.00 g, 4.70 mmol) and
CDI (1.53 g, 9.50 mmol); yield: 0.62 g (51%); Rf = 0.58 (MeOH/
EtOAc, 5:95); light yellow solid: mp 109–110 °C [ref. no mp re-
ported23]; dH (CDCl3, 500 MHz) 1.90 (d, J = 6.9 Hz, 3H, CH3), 3.86
(s, 2H, CH2), 5.41 (q, J = 6.9 Hz, 1H, CH), 6.96 (t, J = 1.3 Hz, 1H),
7.10 (br s, 1H), 7.17–7.19 (m, 1H), 7.29 (br s, 1H), 7.31 (dd,
J = 1.3, 7.6 Hz, 1H), 7.37 (t, J = 7.8 Hz, 1H), 7.53 (bd, J = 7.6 Hz,
1H), 7.63 (bs, 1H), 7.74 (d, J = 7.9 Hz, 1H), 7.76 (d, J = 7.6 Hz, 1H);
dC (CDCl3, 125 MHz) 22.2 (CH3), 36.9 (CH2), 56.8 (CH), 118.0 (CH),
120.0 (CH), 120.1 (CH), 122.6 (CH), 124.8 (CH), 125.0 (CH), 126.8
(CH), 127.0 (CH), 129.2 (CH), 136.0 (CH), 139.9 (Cq), 140.9 (Cq),
141.8 (Cq), 143.3 (Cq), 144.0 (Cq); MS (ESI): m/z = 261 [M++H].
5.5.3.2.
1-[40-(tert-Butyl-dimethyl-silanyloxy)-biphenyl-4-yl]-
propan-1-ol (22b). Synthesized according to method B using 22c
(3.30 g, 10.6 mmol) and 1.0 M EtMgBr (12.7 mL). Yield: 1.89 g
(52%); Rf = 0.40 (PE/EtOAc, 9:1); dH (CDCl3, 500 MHz) 0.23 (s, 6H),
0.95 (t, J = 7.3 Hz, 3H), 1.00 (s, 9H), 1.76–1.89 (m, 2H), 4.64 (t,
J = 6.6 Hz, 1H), 6.90 (d, J = 8.5 Hz, 2H), 7.38 (d, J = 8.5 Hz, 2H),
7.46 (d, J = 8.5 Hz, 2H), 7.54 (d, J = 8.5 Hz, 2H); MS (ESI): m/
z = 344 [M++H].
5.5.2.27. 1-[1-(7-Fluoro-9H-fluoren-2-yl)-ethyl]-1H-imidazole
(33). Synthesized according to Method A using 33a (1.00 g,
4.38 mmol) and CDI (1.87 g, 1.16 mmol); yield: 0.44 g (36%);
Rf = 0.24 (MeOH/EtOAc, 5:95); yellow oil; dH (CDCl3, 500 MHz)
1.90 (d, J = 6.9 Hz, 3H, CH3), 3.85 (s, 2H, CH2), 5.41 (q, J = 7.0 Hz,
1H, CH), 6.96 (s, 1H), 7.05–7.09 (m, 2H), 7.18 (d, J = 7.9 Hz, 1H),
7.22 (dd, J = 1.8, 8.6 Hz, 1H), 7.28 (br s, 1H), 7.63 (br s, 1H),
7.67–7.70 (m, 2H); dC (CDCl3, 125 MHz) 22.2 (CH3), 36.9 (CH2),
56.8 (CH), 112.4 (d, CH), 114.1 (d, CH), 118.0 (CH), 119.8 (CH),
120.9 (CH), 122.6 (CH), 125.0 (CH), 129.2 (CH), 136.0 (CH),
137.0 (Cq), 139.7 (Cq), 141.0 (Cq), 143.7 (Cq), 145.5 (Cq), 161.6
(Cq); MS (ESI): m/z = 279 [M++H].
5.5.3.3. 3-(40-Fluorobiphenyl-4-yl)pentan-3-ol (25a). Synthesized
according to Method B using 23b (0.58 g, 2.53 mmol) and a 1.0 M
ethylmagnesiumbromide solution in THF (25.0 mL, 25.0 mmol);
yield: 0.58 g (89%); Rf = 0.28 (DCM); dH (CDCl3, 500 MHz): 0.79–
0.92 (s, 6H, CH3), 1.68 (s, br, 1H, OH), 1.82–1.93 (m, 4H, CH2),
7.10–7.14 (m, 2H), 7.43–7.45 (m, 2H), 7.51–7.58 (m, 4H); MS
(ESI): m/z = 259 [M++H].
5.5.4. Method C: Suzuki coupling
The corresponding brominated aromatic compound (1 equiv)
was dissolved in toluene (7 mL/mmol), and an aqueous 2.0 M
Na2CO3 solution (3.2 mL/mmol) and an ethanolic solution
(3.2 mL/mmol) of the corresponding boronic acid (1.5–2.0 equiv)
were added. The mixture was deoxygenated under reduced pres-
sure and flushed with nitrogen. After repeating this cycle several
times Pd(PPh3)4 (4 mol%) was added, and the resulting suspension
was heated under reflux for 8 h. After cooling ethyl acetate (10 mL)
and water (10 mL) were added, and the organic phase was sepa-
rated. The water phase was extracted with ethyl acetate (2ꢂ 10
mL). The combined organic phases were washed with brine, dried
over Na2SO4, filtered over a short plug of CeliteÒ, and evaporated
under reduced pressure. The compounds were purified by flash
chromatography on silica gel.
5.5.2.28. 2-(1-Imidazol-1-yl-ethyl)-9H-carbazole (34). Synthe-
sized according to Method A using 34a (0.22 g, 1.02 mmol) and
CDI (0.33 g, 2.04 mmol); yield: 0.08 g (29%); [ref. 157–158 °C23];
Rf = 0.40 (MeOH/EtOAc, 5:95); dH (CDCl3, 500 MHz) 1.90 (d,
J = 6.9 Hz, 3H), 5.46 (q, J = 6.9 Hz, 1H), 6,97 (br s, 1H), 7.05–7.07
(m, 2H), 7.11 (br s, 1H), 7.22 (ddd, J = 1.9, 6.4, 8.0 Hz, 1H), 7.38–
7.43 (m, 2H), 7.65 (br s, 1H), 8.02 (d, J = 8.5 Hz, 1H), 8.05 (d,
J = 7.9 Hz, 1H); dC (CDCl3, 125 MHz) 22.4 (CH3), 57.2 (CH), 108.0
(CH), 110.8 (CH), 117.3 (CH), 118.3 (CH), 119.4 (CH), 120.3 (CH),
120.5 (CH), 122.7 (Cq), 123.1 (Cq), 126.0 (CH), 128.8 (CH),
136.0 (CH), 139.2 (Cq), 140.0 (Cq), 140.2 (Cq); MS (ESI): m/z = 262
[M++H].
5.5.2.29. 2-(1-(1H-Imidazol-1-yl)ethyl)-7-fluoro-9H-carbazole
(35). Synthesized according to Method
A
using 35a (0.30 g,
5.5.4.1. 1-((40-(Trifluoromethyl)biphenyl-4-yl)methyl)-1H-imid-
azole (11). Synthesized according to Method C using 1-(4-bro-
1.30 mmol) and CDI (0.42 g, 2.60 mmol); yield: 0.08 g (23%);
Rf = 0.11 (EtOAc); dH (CDCl3, 500 MHz) 1.93 (d, J = 7.0 Hz, 3H),
5.64 (q, J = 7.0 Hz, 1H), 6.90 (ddd, J = 2.2, 8.5, 9.6 Hz, 1H), 6.99 (t,
J = 1.3 Hz, 1H), 7.07 (ddd, J = 0.6, 1.6, 8.2 Hz, 1H), 7.11 (dd, J = 2.2,
9.6 Hz, 1H), 7.18 (t, J = 1.3 Hz, 1H), 7.28 (d, J = 1.6 Hz, 1H), 7.80
(br s, 1H), 7.96–7.99 (m, 2H); dC (CDCl3, 125 MHz) 22.5 (CH3),
58.6 (CH), 98.2 (d, CH), 107.9 (d, CH), 109.4 (CH), 118.6 (CH),
119.7 (CH), 120.6 (Cq), 121.1 (CH), 122.2 (CH), 123.8 (Cq), 128.9
(CH), 137.4 (CH), 140.4 (Cq), 142.2 (Cq), 142.8 (Cq), 163.5 (Cq); MS
(ESI): m/z = 280 [M++H].
mobenzyl)-1H-imidazole
(0.24 g,
1.00 mmol)
and
4-trif-
luoromethylphenylboronic acid (0.38 g, 2.00 mmol); yield: 0.24 g
(80%); brown oil; Rf = 0.14 (EtOAc); dH (CDCl3, 500 MHz) 5.17 (s,
2H, CH2), 6.93 (br s, 1H), 7.11 (br s, 1H), 7.24 (d, J = 7.9 Hz, 2H),
7.57 (d, J = 7.9 Hz, 2H), 7.59 (br s, 1H), 7.65 (d, J = 8.5 Hz, 2H),
7.68 (d, J = 8.5 Hz, 2H); dC (CDCl3, 125 MHz) 50.4 (CH2), 119.2
(CH), 123.1 (Cq), 125.2 (Cq), 125.7 (CH), 127.3 (CH), 127.7 (CH),
127.8 (CH), 129.8 (CH), 136.2 (Cq), 137.4 (CH), 139.7 (Cq), 143.8
(Cq); MS (ESI): m/z = 303 [M++H].

Q. Hu et al. / Bioorg. Med. Chem. 16 (2008) 7715–7727
7725
5.5.4.2. 1-(40-Fluorobiphenyl-4-yl)propan-1-one (23b). Synthesized
according to Method C using 4-bromopropiophenone (1.23 g,
6.65 mmol) and 4-fluorophenylboronic acid (1.38 g, 6.47 mmol);
yield: 1.20 g (79%); Rf = 0.45 (Hex/EtOAc, 10:1); dH (CDCl3,
500 MHz) 1.24–1.27 (t, J = 7.3 Hz, 3H, CH3), 3.01–3.06 (m, 2H,
CH2), 6.97–7.01 (m, 1H), 7.06–7.11 (m, 1H), 7.58–7.61 (m, 2H),
8.02–8.04 (m, 2H); MS (ESI): m/z = 229 [M++H].
brine, dried over Na2SO4, and evaporated under reduced pressure.
The crude products were purified by flash chromatography on sil-
ica gel; yield: 0.22 g (95%); Rf = 0.35 (PE/EtOAc, 2:1); the com-
pound was directly used in the next step without further
purification and analysis.
5.5.5.5. N-[40-(1H-Imidazol-1-yl-propyl)-biphenyl-4-yl]-acetamide
(21). To a solution of 21a (0.07 g, 0.25 mmol) in THF (10 mL) were
added DMAP (0.02 g, 0.13 mmol) and triethylamine (0.1 mL). After
cooling to 0 °C in an ice bath, acetyl chloride was dropped into the
reaction solution slowly. Then, it was stirred in the ambient temper-
ature overnight. After being neutralized to pH 7 with sodium bicar-
bonate in an ice bath, ethyl acetate (10 mL) and water (10 mL)
were added, and the organic phase was separated. The organic phase
was extracted with water and brine, dried over Na2SO4 and evapo-
rated under reduced pressure. The crude products were purified by
flash chromatography on silica gel; yield: 0.33 g (23%); white solid:
mp 221–223 °C; Rf = 0.27 (DCM/MeOH, 20:1); dH (CDCl3, 500 MHz)
0.97 (t, J = 7.3 Hz, 3H, CH3), 2.20 (s, 3H, CH3CO), 2.26 (q, J = 7.3,
7.6 Hz, 2H, CH2), 5.05 (t, J = 7.6 Hz, 1H, CH), 6.99 (s, 1H), 7.11 (s,
1H), 7.23 (d, J = 8.2 Hz, 2H), 7.49–7.58 (m, 6H), 7.72 (s, 1H); dC (CDCl3,
125 MHz) 11.0 (CH3), 24.6 (CH3CO), 28.5 (CH2), 63.2 (CH), 120.1,
126.9, 127.5, 127.5, 135.9, 137.6, 140.5, 168.4; MS (ESI): m/z = 320
[M++H].
5.5.4.3. 1-(40-Fluoro-2’-nitrobiphenyl-4-yl)ethanone (35c). Syn-
thesized according to Method C using 4-fluoro-1-iodo-2-nitroben-
zene (1.20 g, 4.50 mmol) and 4-acetylbenzeneboronic acid (1.48 g,
9.00 mmol); yield: 1.01 g (87%); Rf = 0.19 (petrolether/EtOAc,
10:1); dH (CDCl3, 500 MHz) 2.64 (s, 3H, CH3), 7.38 (d, J = 8.5 Hz,
2H), 7.39–7.41 (m, 1H), 7.43 (dd, J = 5.5, 8.5 Hz, 1H), 7.67 (dd,
J = 2.5, 8.0 Hz, 1H), 8.01 (d, J = 8.5 Hz, 2H); dC (CDCl3, 125 MHz)
26.6 (CH3), 112.1 (d, CH), 119.9 (d, CH), 128.3 (CH), 128.7 (CH),
131.7 (Cq), 133.2 (CH), 136.8 (Cq), 141.3 (Cq), 161.6 (d, Cq), 197.4
(Cq ); MS (ESI): m/z = 259 [M+-H].
5.5.5. Method D: reduction with NaBH4
To an ice-cooled solution of the corresponding aldehyde or ke-
tone (1 equiv) in methanol (5 mL/mmol) was added NaBH4
(2 equiv). Then, the resulting mixture was heated to reflux for
30 min. After cooling to ambient temperature, the solvent was dis-
tilled off under reduced pressure. Subsequently water (10 mL) was
added, and the resulting mixture was extracted with ethyl acetate
(3ꢂ 10 mL). The combined organic phases were washed with
brine, dried over MgSO4, and evaporated under reduced pressure.
Then, the desired product was purified by chromatography on sil-
ica gel.
5.5.5.6. 40-(1H -Imidazol-1-yl-propyl)-biphenyl-4-ol (22). To
a
solution of 22a (0.85 g, 2.16 mmol) in anhydrous THF (20 mL)
was added TBAF (2.4 mL, 2.4 mmol), and subsequently the solution
was stirred at room temperature for 4 h. The reaction were termi-
nated with the addition of methanol, and the solvent was removed
under reduced pressure. Then, the desired product was purified by
chromatography on silica gel. Yield: 0.22 g (37%); Yellow solid;
Rf = 0.21 (Hex/EtOAc, 5:1); dH (DMSO-d6, 500 MHz) 0.82 (t,
J = 7.3 Hz, 3H), 2.21 (m, 2H), 5.23 (t, J = 7.3 Hz, 1H), 6.82 (d,
J = 8.8 Hz, 2H), 6.90 (s, 1H), 7.37 (d, J = 8.5 Hz, 2H), 7.46 (d,
J = 8.8 Hz, 2H), 7.54 (d, J = 8.5 Hz, 2H), 7.82 (s, 1H), 9.55 (s, 1H);
dC (DMSO-d6, 125 MHz) 10.9 (CH3), 27.4 (CH2), 61.5 (CH), 115.6
(CH), 117.7 (CH), 126.0 (CH), 127.1 (CH), 127.6 (CH), 128.4 (Cq),
130.3 (CH), 130.7 (Cq), 139.3 (CH), 139.5 (Cq), 157.1 (Cq); MS
(ESI): m/z = 279 [M++H].
5.5.5.1. 1-(40-Fluoro-biphenyl-4-yl)-propan-1-ol (23a). Synthesized
according to Method D using 22b (1.20 g, 5.26 mmol) and NaBH4
(0.30 g, 7.89 mmol); yield: 1.15 g (95%); the compound was directly
used in the next step without further purification and characterization.
5.5.5.2. 1-(9H-Carbazol-2-yl)ethanol (34a). Synthesized accord-
ing to Method D using 1-(9H-carbazol-2-yl)ethanone (0.50 g,
2.39 mmol) and NaBH4 (0.16 g, 4.30 mmol); yield: 0.42 g (83%);
Rf = 0.12 (petrolether/EtOAc, 5:1); light yellow solid: mp 192–
194 °C; dH (CDCl3, 500 MHz) 1.41 (d, J = 6.6 Hz, 3H, CH3), 3.13 (br
s, 1H), 4.88 (q, J = 6.6 Hz, 1H), 7.03 (ddd, J = 1.2, 7.3, 7.9 Hz, 1H),
7.07 (dd, J = 1.6, 8.2 Hz, 1H), 7.22 (ddd, J = 1.2, 7.2, 8.2 Hz, 1H),
7.30 (dt, J = 1.0, 8.2 Hz, 1H), 7.37–7.39 (m, 1H), 7.85 (d, J = 8.2 Hz,
1H), 7.88 (d, J = 7.9 Hz, 1H), 9.62 (br s, 1H); dC (CDCl3, 125 MHz)
25.5 (CH3), 69.9 (CH2), 107.3 (CH), 110.4 (CH), 116.4 (CH), 118.4
(CH), 119.5 (CH), 119.6 (CH), 121.8 (Cq), 122.6 (Cq), 124.9 (CH),
139.7 (Cq), 139.8 (Cq), 144.4 (Cq); MS (ESI): m/z = 210 [M+ꢁOH].
5.5.5.7. 3-(40-Fluorobiphenyl-4-yl)-3-(1H-imidazol-1-yl)propan-
1-ol (26). Compound 26a (0.241 g, 0.45 mmol) was dissolved by
slowly adding dropwise to 15 mL THF and 1 M TBAF (0.55 mL,
0.55 mmol) in THF. One hour later, according to TLC (DCM/metha-
nol, 95:5), the deprotection was quantitative. The batch was di-
luted with a large quantity of ethyl acetate and extracted three
times with water and once with brine, then dried over MgSO4,
and the solvent removed under reduced pressure. The crude prod-
uct was subsequently purified by column chromatography; yield:
0.09 g (67%); Rf = 0.34 (DCM/MeOH, 9:1); dH (CDCl3, 500 MHz)
2.43–2.49 (m, 2H, CH2), 3.50–3.54 (m, 1H), 3.68–3.72 (m, 1H),
5.56–5.59 (q, 1H, CH), 6.98 (m, 1H), 7.08 (m, 1H0), 7.1–7.14 (m,
2H), 7.26–7.29 (m, 2H), 7.48–7.51 (m, 4H), 7.56 (m, 1H); dC (CDCl3,
125 MHz) 37.1 (CH2), 50.5 (CH), 57.7 (CH2-OH), 116.3, 127.6, 128.6,
129.8, 136.8, 137.2, 139.9, 140.0, 161.4; MS (ESI): m/z = 297
[M++H].
5.5.5.3. 1-(7-Fluoro-9H-carbazol-2-yl)ethanol (35a). Synthesized
according to Method D using 35b (0.25 g, 1.12 mmol) and NaBH4
(0.08 g, 2.02 mmol); yield: 0.21 g (82%); Rf = 0.19 (petrolether/EtOAc,
5:1); dH (CDCl3, 500 MHz) 1.50 (d, J = 6.4 Hz, 3H), 4.94 (q, J = 6.4 Hz,
1H), 6.85 (ddd, J = 2.3, 8.5, 8.8 Hz, 1H), 7.08 (dd, J = 2.3, 9.8 Hz, 1H),
7.15 (dd, J = 1.2, 8.2 Hz, 1H), 7.43 (br s, 1H), 7.91 (d, J = 8.5 Hz, 1H),
7.93 (dd, J = 5.5, 8.5 Hz, 1H); dC (CDCl3, 125 MHz) 26.0 (CH3), 71.5
(CH), 98.0 (d, CH), 107.5 (d, CH), 108.6 (CH), 118.2 (CH), 120.5 (CH),
120.8 (Cq), 121.8 (d, CH), 123.2 (Cq), 142.2 (Cq), 142.4 (Cq), 145.1
(Cq), 163.2 (d, Cq); MS (ESI): m/z = 212 [M+ꢁOH].
5.5.5.8. 1-(3-Chloro-1-(40-fluorobiphenyl-4-yl)propyl)-1H-imid-
azole (27). Compound 26 (0.044 g, 0.148 mmol) was dissolved in
5.5.5.4. 40-(1H-Imidazol-1-yl-propyl)-biphenyl-4-ylamine
(21a). To a solution of 20 (0.32 g, 0.85 mmol) in DCM (10 mL)
was added TFA (0.63 mL, 8.5 mmol) slowly in an ice bath. Subse-
quently it was stirred at room temperature overnight. DCM
(10 mL) and water (10 mL) were added and the organic phase
was separated. The organic phase was extracted with water and
10 mL dry DCM and mixed with 13 lL thionyl chloride. The batch
was stirred for 2 h at room temperature; according to the TLC con-
trol, the reaction was quantitative (DCM as solvent). The batch was
diluted with a large quantity of DCM and water. The organic phase
was separated off and extracted five times with water and once
with brine, then dried over MgSO4, and the solvent removed under

7726
Q. Hu et al. / Bioorg. Med. Chem. 16 (2008) 7715–7727
reduced pressure; yield: 0.05 g (99%); Rf = 0.63 (DCM/MeOH, 9:1);
dH (CDCl3, 500 MHz) 2.87–2.97 (m, 2H, CH2), 3.50–3.60 (m, 2H,
CH2Cl), 5.80–5.83 (m, 1H, CH), 7.11–7.16 (m, 2H), 7.16–7.17 (m,
1H), 7.35–7.37 (m, 1H), 7.49–7.53 (m, 4H), 7.58–7.60 (m, 2H),
9.51–9.53 (m, 1H); dC (CDCl3, 125 MHz) 34.2 (CH2), 41.4 (CH2Cl),
61.8 (CH), 119.6, 122.9, 116.5, 128.4, 129.4, 135.7, 136.3, 137.6,
136.4, 142.5, 163.5; MS (ESI): m/z = 315 [M++H].
maximum of 2.5 Å between the nitrogen of the imidazole and
the iron was set.
Ligands were docked in 50 independent genetic algorithm (GA)
runs using GOLD. Heme iron was chosen as active-site origin, while
the active site radius was set equal to 19 Å. The automatic active-
site detection was switched on. A distance constraint of a mini-
mum of 1.9 and a maximum of 2.5 Å between the sp2-hybridized
nitrogen of the imidazole and the iron was set. Furthermore, some
of the GOLDSCORE parameters were modified to improve the
weight of hydrophobic interaction and of the coordination be-
tween iron and nitrogen. The genetic algorithm default parameters
were set as suggested by the GOLD authors. On the other hand, the
annealing parameters of fitness function were set at 3.5 Å for
hydrogen bonding and 6.5 Å for van der Waals interactions.
5.5.5.9. 1-(7-(tert-Butyldimethylsilyloxy)-9H-fluoren-2-yl)ethan-
one, (30c). Imidazole (0.17 g, 2.45 mmol) and 1-(7-hydroxy-9H-
fluoren-2-yl)ethanone (0.50 g, 2.23 mmol) were dissolved in
20 mL DCM. Then, tert-butyldimethylsilylchloride (0.37 g,
2.45 mmol) dissolved in 3 mL DCM was slowly added. The result-
ing mixture was stirred for 18 h at room temperature. Afterwards
the mixture was extracted with water and brine. The organic phase
was separated, dried over Na2SO4 and evaporated; yield: 0.58 g
(77%); Rf = 0.40 (petrolether/EtOAc, 10:1); MS (ESI): m/z = 339
[M++H].
All 50 poses for each compound were clustered with ACIAP26
,
and the representative structure of each significant cluster was se-
lected. The quality of the docked representative poses was evalu-
ated based on visual inspection of the putative binding modes of
the ligands, as outcome of docking simulations and cluster analy-
sis. Further the different interaction patterns were manually ana-
lyzed using Silver 1.1,25b a program included for use with GOLD
and used to post-process docking results.
5.5.5.10. 7-(1-(1H-imidazol-1-yl)ethyl)-9H-fluoren-2-ol (30). Com-
pound 30a (0.16 g, 0.40 mmol) was dissolved in 10 mL THF, and 1 M
TBAF (0.41 mL, 0.41 mmol) solution in THF was added dropwise. After
1 h according to TLC (DCM/methanol 95:5) the deprotection was
quantitative. The batch was diluted with a large quantity of ethyl ace-
tate and extracted three times with water and once with brine, then
dried over MgSO4, and the solvent removed under reduced pressure;
yield: 0.10 g (90%); Rf = 0.12 (MeOH/EtOAc, 5:95); orange solid: mp
217–218 °C; dH (CDCl3, 500 MHz) 1.81 (d, J = 6.9 Hz, 3H), 3.70 (s,
2H), 5.31 (q, J = 6.9 Hz, 1H), 6.77 (dd, J = 2.2, 8.2 Hz, 1H), 6.90 (s,
1H), 6.93 (s, 1H), 6.95 (s, 1H), 7.06 (d, J = 7.9 Hz, 1H), 7.18 (s, 1H),
7.50 (d, J = 8.2 Hz, 1H), 7.52 (d, J = 7.9 Hz, 1H), 7.55 (s, 1H); dC (CDCl3,
125 MHz) 21.9 (CH3), 36.6 (CH2), 56.9 (CH), 112.0 (CH), 114.1 (CH),
118.1 (CH), 118.8 (CH), 120.6 (CH), 122.4 (CH), 124.7 (CH), 128.2
(CH), 132.8 (Cq), 135.6 (CH), 137.9 (Cq), 142.0 (Cq), 143.2 (Cq), 145.2
(Cq), 156.6 (Cq); MS (ESI): m/z = 277 [M++H].
Acknowledgments
The authors thank Ulrike E. Hille and Dr Carsten Jagusch for
their help in the synthesis of some compounds, and Maria-Chris-
tina Scherzberg for the IC50 determination of some compounds.
We also are grateful to Professor J. Hermans, Cardiovascular Re-
search Institute, University of Maastricht, Netherlands, for provid-
ing us with V79MZh11B1 cells expressing human CYP11B1 and
Professor R. Bernhardt, Saarland University, Germany, for making
us V79MZh11B2 cells expressing human CYP11B2 available. This
research was supported in part by the Fonds der Chemischen
Industrie.
5.5.5.11. 1-(7-Fluoro-9H-carbazol-2-yl)ethanone (35b). 35c was
dissolved in 3 mL P(OEt)3 and refluxed for 16 h. The resulting mix-
ture was directly purified using column chromatography; yield:
Supplementary data
The synthetic procedures and characterization of further inter-
mediates and IR spectra of all compounds as well as the purities of
final compounds by element analysis or HPLC can be found, in the
online version, at doi:10.1016/j.bmc.2008.07.011.
0.28
g (53%); Rf = 0.13 (petrolether/EtOAc, 5:1); dH (CDCl3,
500 MHz) 2.54 (s, 3H), 6.79 (ddd, J = 2.3, 8.6, 9.5 Hz, 1H), 7.01
(dd, J = 2.3, 9.6 Hz, 1H), 7.65 (dd, J = 1.6, 8.2 Hz, 1H), 7.85 (dd,
J = 5.4, 8.5 Hz, 1H), 7.87 (d, J = 8.5 Hz, 1H), 7.93 (dd, J = 0.6,
1.6 Hz, 1H), 10.53 (br s, 1H); dC (CDCl3, 125 MHz) 26.5 (CH3),
97.4 (d, CH), 107.3 (d, CH), 110.9 (CH), 118.4 (Cq), 119.0 (CH),
119.2 (CH), 121.6 (d, CH), 126.2 (Cq), 133.6 (Cq), 139.7 (Cq), 142.0
(d, Cq), 162.2 (d, Cq), 197.8 (Cq); MS (ESI): m/z = 227 [M++H].
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