3346 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 17
Brief Articles
2-Iod o-4-n itr oben za m id e (3). A mixture of 2 (6.60 g, 22.5
mmol) and SOCl2 (100 mL) was heated at 60 °C for 3 h under
argon and concentrated by rotoevaporation. Residual SOCl2
was removed from the crude product mixture by coevaporation
with dry CHCl3 (3 × 50 mL). Concentrated aqueous NH3 (100
mL) was then added and the mixture stirred overnight at
ambient temperature. The precipitate was filtered, rinsed with
H2O and dried in an oven at 60 °C. The crude product was
purified by flash chromatography (75% EtOAc in hexane) to
give 5.6 g (85%) of 3 as cream-colored crystals: mp 208-209
°C (EtOAc); 1H NMR (CD3OD) δ 8.70 (d, 1H, J ) 2.2, H-3),
8.29 (dd, 1H, J ) 8.5, 2.2, H-5), 7.59 (d, 1H, J ) 8.4, H-6).
Anal. (C7H5N2O3I) C, H, N.
activity has been observed for the structurally similar
antiandrogen RU 56187.13
Although our initial design strategy of DTIB was
based on the similar hydrophobicity of iodine and
trifluoromethyl, it must be noted that these functional
groups do not share similar electronic and steric proper-
ties. In particular, iodine is less electronegative (σm, σp
values are 0.35 and 0.18, respectively, for iodine versus
0.43 and 0.54, respectively, for CF3) and has a 3-fold
larger steric size than trifluoromethyl (molar refractivity
values for iodine and CF3 are 13.9 and 5.0, respec-
tively).9 Our binding affinity data therefore indicate that
the AR binding domain that interacts with the trifluo-
romethyl substituent in RU 59063 is sufficiently large
to accommodate the increased steric bulk of an iodine
atom. Taken together, these results suggest that steric
and hydrophobic interactions may be more important
than electronic interactions at this binding region for
high AR binding in this class of nonsteroidal ligands.
2-Iod o-4-n itr oben zon itr ile (4). A mixture of 3 (5.5 g, 18.8
mmol) and SOCl2 (35 mL) was refluxed for 3 h under argon
and concentrated under reduced pressure. The residue was
purified by flash chromatography (20% EtOAc in hexane) to
give 4.12 g (80%) of 4 as cream-colored crystals: mp 154-155.5
1
°C [EtOAc:hexane (1:4)]; H NMR (CDCl3) δ 8.76 (d, 1H, J )
2.2, H-3), 8.32 (dd, 1H, J ) 8.5, 2.2, H-5), 7.82 (d, 1H, J ) 8.6,
H-6). Anal. (C7H3N2O2I) C, H, N.
4-Cya n o-3-iod oa n ilin e (5). A mixture of 4 (2.3 g, 8.4 mmol)
and SnCl2‚2H2O (9.3 g, 41.4 mmol) in EtOH (35 mL) was
refluxed for 2 h. The mixture was concentrated under reduced
pressure and treated with H2O (100 mL) and the pH was
adjusted to 9 by treatment with 5% aqueous NaHCO3. The
mixture was extracted with EtOAc; the organic layers were
washed with saturated brine and H2O and dried. The residue
obtained after removal of solvent was purified by flash
chromatography (40% EtOAc in hexane) to afford 2 g (98%) of
5 as white fluffy crystals: mp 146-148 °C [EtOH:H2O (1:5)];
1H NMR (CDCl3) δ 7.33 (d, 1H, J ) 8.5, H-5), 7.14 (d, 1H, J )
2.3, H-2), 6.62 (dd, 1H, J ) 8.5, 2.2, H-6), 4.19 (br s, 2H,
exchangeable with D2O, NH2). Anal. (C7H5N2I) C, H, N.
2-Iod o-4-isoth iocya n a toben zon itr ile (6). A solution of 5
(0.54 g, 2.2 mmol) in THF (10 mL) was added dropwise at
ambient temperature to a well-stirred suspension of thiophos-
gene (0.30 g, 2.6 mmol) in H2O (5 mL). TLC analysis [silica;
hexane:EtOAc (6:1)] at 3 h indicated completeness of reaction.
The mixture was diluted with H2O (20 mL), extracted with
CHCl3 (2 × 20 mL) and dried. The residue obtained after
removal of solvent was dried under high vacuum to afford a
quantitative yield of a yellow-brown solid which was used
directly in the next step. A small portion of the crude product
was purified by flash chromatography (15% EtOAc in hexane)
to give an analytical sample of 6 as a white solid: mp 116-
118 °C; 1H NMR (CDCl3) δ 7.76 (d, 1H, J ) 2.1, H-3), 7.58 (d,
1H, J ) 8.3, H-6), 7.26 (dd, 1H, J ) 8.3, 2.1, H-5); HRMS (EI)
calcd for C8H3N2IS (M+) 285.9062, found 285.9058.
Con clu sion s
In summary, the present study has identified a new
iodinated nonsteroidal AR ligand, DTIB, which demon-
strates subnanomolar binding affinity and potent ago-
nist activity in in vitro AR binding and functional
assays, respectively. These studies also suggest the
existence of a large hydrophobic pocket in the AR
binding domain that interacts with the meta substituent
of this pharmacophore. Studies are currently underway
to evaluate the utility of radioiodinated analogues of
DTIB as radioligands for in vitro and in vivo studies of
AR.
Exp er im en ta l Section
Gen er a l Meth od s. Melting points were determined with
a Thomas-Hoover melting point apparatus and are uncor-
rected. 1H NMR spectra were obtained in either CDCl3 or CD3-
OD with a Bruker WM-360 (360 MHz) instrument using
tetramethylsilane (TMS) as internal standard. Chemical shifts
(δ) are reported in parts per million (ppm) relative to TMS,
and coupling constants (J ) are reported in hertz (Hz). Elemen-
tal analyses were performed by the Department of Chemistry,
University of Michigan, and were within (0.4% of the calcu-
lated values. RU 59063 and 2-(4-hydroxybutylamino)-2-cyano-
propane were synthesized as previously described.8 All other
chemical reagents were obtained from Aldrich Chemical Co.,
Milwaukee, WI, and were used without further purification.
Organic extracts were dried over anhydrous Na2SO4 and
concentrated to dryness by rotoevaporation under reduced
pressure.
4-[4,4-Dim eth yl-3-(4-h yd r oxybu tyl)-5-im in o-2-th ioxo-1-
im id a zolid in yl]-2-iod oben zon itr ile (7). A solution of 2-(4-
hydroxybutylamino)-2-cyanopropane8 (0.30 g, 1.94 mmol) in
anhydrous THF (2 mL) was added dropwise at ambient
temperature to a stirred solution of the crude isothiocyanate
6 (0.55 g, 1.94 mmol) and Et3N (25 mg, 0.25 mmol) in
anhydrous THF (2 mL). The reaction mixture was refluxed
for 1 h, at which point, TLC analysis [silica; hexanes:EtOAC
(6:1)] indicated completeness of reaction. The reaction mixture
was concentrated under reduced pressure and the residue
purified by flash chromatography (35% acetone in chloroform)
to provide 0.55 g (64%) of the title compound 7 as a straw-
colored viscous liquid: 1H NMR (CDCl3) δ 7.93 (s, 1H, Ar-H),
7.75 (d, 1H, J ) 8.3, Ar-H), 7.49 (d, 1H, J ) 8.2, Ar-H), 3.75-
3.66 (m, 4H, -NCH2- and -CH2O-), 1.92 (m, 2H, CH2), 1.66
(m, 2H, CH2), 1.58 (s, 6H, C(CH3)2); HRMS (EI) calcd for
2-Iod o-4-n itr oben zoic Acid (2). A vigorously stirred slurry
of 2-amino-4-nitrobenzoic acid (10 g, 55 mmol) and aqueous 9
N H2SO4 (64 mL) was diazotized at 0 °C (ice-salt bath) by
dropwise addition of a solution of NaNO2 (4.17 g, 60.4 mmol)
in water (50 mL). The mixture was stirred at 0 °C for 1 h and
treated with urea (1.1 g, 18.3 mmol) to destroy excess HNO2.
A solution of NaI (9.9 g, 66 mmol) in H2O (50 mL) was then
added dropwise at 0-5 °C. The reaction was allowed to warm
to ambient temperature, stirred a further 2 h, diluted with
1% aqueous NaHSO3 solution (200 mL) and filtered. The crude
product was rinsed with hot EtOAc (3 × 100 mL) to remove a
dark orange side product and the residue was purified by flash
chromatography [gradient elution with EtOAc:hexane:glacial
acetic acid (30:70:1 to 80:20:1)] to give 6.8 g (42%) of 2 as light
C
16H19N4ISO (M+) 442.0324, found 442.0320.
4-[4,4-Dim et h yl-3-(4-h yd r oxyb u t yl)-5-oxo-2-t h ioxo-1-
im id a zolid in yl]-2-iod oben zon itr ile (DTIB, 1). A solution
of the imine derivative 7 (0.48 g, 1.1 mmol) in CH3OH (8 mL)
was treated with aqueous 2 N HCl (1 mL) and refluxed for 1
h. The cooled reaction mixture was poured into H2O (80 mL)
and extracted with EtOAc (2 × 50 mL), and the organic layers
dried and concentrated under reduced pressure. The crude
product was purified by flash chromatography (70% EtOAc in
1
yellow needles: mp 143.5-145 °C [benzene:hexane (1:1)]; H
NMR (CD3OD) δ 8.77 (d, 1H, J ) 2.2, H-3), 8.30 (dd, 1H, J )
8.5, 2.2, H-5), 7.92 (d, 1H, J ) 8.5, H-6). Anal. (C7H4NO4I) C,
H, N.