374 Steroidal P450 inhibitors
Arch. Pharm. Pharm. Med. Chem. 2001, 334, 373–374
described by Potter et al. who used 4-bromopyridine for the
preparation of lithium trimethoxy(4-pyridyl)boronate.
Acknowledgements
Thanks are due to the Fonds der Chemischen Industrie, who
supported this work by a grant, and to Mrs Anja Palusczak for
her help in performing the biological assays. We would also like
to thank the University of Damascus, Syria, for the scholarship
to SH.
The acetyl group of 1 was removed using aqueous
methanolic NaOH to afford the target compound 2[8]. Com-
pound 3[9] was prepared directly from 2 by applying Op-
penauer oxidation using cyclohexanone and aluminum
isopropoxide. Abiraterone was synthesized as described in
the literature[4]
.
Supplementary material available
Experimental procedures, NMR spectra, and analytical data are
available on request.
As shown in Table 1, compounds 1 and 2 are approximately
two to three times more active than the steroidal inhibitor
Abiraterone. The progesterone derivative 3 which also
exceeds the activity of Abiraterone shows also inhibitory
activity toward two other isozymes involved in androgen
biosynthesis, 5α reductase type 1 and 2 (which convert
testosterone into dihydrotestosterone, IC50 type 1 = 2.4 µM
and type 2 = 0.49 µM). Being a dual inhibitor toward P450
17 and 5α-reductase, compound 3 might be more advan-
tageous clinically.
References
[1] S. Nakajin, J. E. Shively, P. M. Yuan, P. F Hall, Biochemistry
1981, 20, 4037–4042.
[2] J. Trachtenberg, N. Halpern, A. Pont, J. Urol. 1984, 132,
61–63.
[3] For review see: R. W. Hartmann, P. B. Ehmer, S. Haidar, M.
Hector, J. Jose, C. D. P. Klein, S. Seidel, T. F. Sergejew, B.
G. Wachall, G. A. Wächter, Y. Zhuang, Arch. Pharm. Pharm.
Med. Chem. 2002, in press.
A precondition for in vivo activity is the ability of the com-
pounds to permeate cell membranes. Therefore compound
2 and Abiraterone were tested for inhibition of the target
enzyme using the whole cell assay recently developed by
our group[10]. Employing E. coli cells coexpressing human
CYP17andNADPH-P450-reductase[10], compound 2 turn-
ed out to be more active than Abiraterone in this assay as
well (IC50 values: 2, 33 nM; Abiraterone, 54 nM).
[4] G. A. Potter, E. S. Barrie, M. Jarman, M. G. Rowlands, J. Med.
Chem. 1995, 38, 2463–2471.
[5] R. W. Hartmann, M. Hector, B. G. Wachall, A. Palusczak, M.
Palzer, V. Huch, M. Veith, J. Med. Chem. 2000, 43, 4437–
4445.
[6] R. W. Hartmann, M. Hector, S. Haidar, P. B. Ehmer, W.
Reichert, J. Jose, J. Med. Chem. 2000, 43, 4266–4277, and
references cited herein.
Table 1. Inhibitory activity of 1–3, Abiraterone, and Ketoconazole
toward human P450 17.
[7] (1): 3β-Acetoxy-17-(5-pyrimidyl)androsta-5,16-diene: mp
164–166 °C. 1H-NMR (CDCl3): δ 1.06 (s, H-19, 3H); 1.08 (s,
H-18, 3H); 2.04 (s, CH3CO, 3H) 4.61 (m, H-3α, 1H); 5.41 (s,
H-6, 1H); 6.25 (s, H-16, 1H); 8.86 (s, pyrimidyl H-3, H-5, 2H);
9.14 (s, pyrimidyl H-2, 1H). IR (KBr) cm–1 : νmax 1735 (C=O
str). HPLC: UV-DAD (Nucleoside RP 18 HD 100-3, 125 × 4
mm, H2O, acetonitrile, 55/45, 0.1% TEA, flow: 0.9 ml, pres-
sure: 19.5 MPa ± 0.2 MPa, tR= 12.5 min.).
————————————————————————————–
Compound
————————————————————————————–
IC50a (nM)
1
38
24
2
3
44
Abiraterone
Ketoconazole
73
[8] (2): 17-(5-pyrimidyl)androsta-5,16-diene-3β-ol: mp 240–
242 °C. 1H-NMR (CDCl3): δ 1.05 (s, H-19, 3H); 1.07 (s, H-18,
3H); 3.54 (m, H-3α, 1H); 5.39 (s, H-6, 1H); 6.18 (s, H-16, 1H);
8.81 (s, pyrimidyl H-3, H-5, 2H); 9.12 (s, pyrimidyl H-2, 1H).
IR (KBr) cm–1 : νmax 3350 (OH str). HPLC: UV-DAD (Nucleo-
side RP 18 HD 100-5, 250 × 4 mm, H2O, acetonitrile, 55/45,
0.1% TFA, flow: 1.0 ml, pressure: 21.3 MPa ± 0.2 MPa, tR=
15.3 min.).
740
————————————————————————————–
a Concentration of inhibitor required to give 50% inhibition. Human
testicular microsomes; concentration of progesterone (substrate)
25 µM. The method described by us was used (ref. 11). The given
values are mean values of at least two experiments, deviation was
within ±5%.
[9] (3): 17-(5-pyrimidyl)androsta-4,16-diene-3-one: mp 196–
198 °C. 1H-NMR (CDCl3): δ 1.05 (s, H-19, 3H); 1.07 (s, H-18,
3H); 5.75 (s, H-4, 1H); 6.18 (s, H-16, 1H); 8.81 (s, pyrimidyl
For the inhibitory activity of these kinds of inhibitors, the
heterocyclic nitrogen plays an important role as it is binding
in a coordinate way to the heme iron of the enzyme.
Interestingly, the pyrimidine group is more appropriate for
potent inhibition than the pyridine moiety, although electron
density of the pyrimidine N is lower than that of pyridine.
Summarizing, we propose that pyrimidine analogs of Abi-
raterone might be superior for clinical use.
H-3, H-5, 2 H); 9.13 (s, pyrimidyl H-2, 1H). IR (KBr) cm–1
:
νmax 1675 (C=O str). HPLC: UV-DAD (Nucleoside RP 18 HD
100-5, 250 × 4 mm, H2O, acetonitrile, 63/37, 0.1% TFA, flow:
1.0 ml, pressure: 21.3 MPa ± 0.2 MPa, tR= 30.7 min.).
[10] P. B. Ehmer, J. Jose, R. W. Hartmann, J. Steroid Biochem.
Molec. Biol. 2000, 75, 57–63.
[11] T. Sergejew, R. W. Hartmann, J. Enzyme Inhib. 1994, 8,
113–122.