1926 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 9
Notes
Ta ble 3. Ratio of AR IC50 and ALR IC50 of Compounds 1
was dried over anhydrous Na2SO4 and passed through a short
silica gel pad. Evaporation of the solvent followed by recrys-
tallization from hexane-EtOAc gave 4c as yellow crystals
IC50 (M)
ARa
ALRb
IC50(ALR)/IC50(AR)
1
compd
1c
1c
1h
(20.3 g, 82%): mp 161-163 °C; H NMR δ 4.78 (s, 2H, CH2),
7.62-8.26 (m, 4H, Ar-H), 12.08 (s, 1H, NH); IR (KBr, cm-1
)
1.3 × 10-7
6.2 × 10-8
5.0 × 10-8
1.0 × 10-7
2.1 × 10-8
1.1 × 10-7
1.0 × 10-4
>1.0 × 10-4
>1.0 × 10-4
4.6 × 10-5
1.5 × 10-6
3.2 × 10-5
769
>1613
>2000
460
1738 (CdO), 1527 (NO2), 1336 (NO2); MS m/ z 249 (M+). Anal.
(C10H7N3O5) C, H, N.
E t h yl 3-(3-Nit r ob en zyl)-2,4,5-t r ioxoim id a zolid in e-1-
a ceta te (5c). The parabanic acid 4c (n ) 1, X ) NO2; 24.9 g,
100 mmol) and ethyl bromoacetate (8; 17 mL, 154 mmol) were
added to a solution of KOH (8.0 g, 120 mmol) in EtOH (600
mL). After being refluxed for 8 h, the mixture was allowed to
cool to 0 °C and filtered. The solid was dissolved in EtOAc
and washed with H2O and brine. The organic phase was dried
over anhydrous Na2SO4 and passed through a short silica gel
pad. After being condensed, the crude solid was recrystallized
from hexane-EtOAc to give 5c as yellow crystals (17.6 g,
53%): 1H NMR δ 1.21 (t, J ) 7.2 Hz, 3H, CH3), 4.17 (q, J )
7.2 Hz, 2H, OCH2), 4.41 (s, 2H, NCH2CO2), 4.91 (s, 2H, CH2-
Ar), 7.64-8.26 (m, 4H, Ar-H); IR (KBr, cm-1) 1740 (CdO), 1720
(CdO), 1525 (NO2), 1350 (NO2); MS m/ z 335 (M+).
Meth od B: Eth yl Ur eid oa ceta te (7). A solution of
glycine ethyl ester hydrochloride (6; 1000 g, 7.16 mol) and urea
(750 g, 12.5 mol) in water (600 mL) was refluxed for 5 h. The
reaction mixture was left standing at ambient temperature.
The solid was filtered and rinsed well with H2O. Recrystal-
lization from H2O (600 mL) gave the urea 7 as white crystals
(734 g, 70%): mp 139-140 °C; 1H NMR δ 1.19 (t, J ) 7.0 Hz,
3H, CH3), 3.73 (d, J ) 6.0 Hz, 2H, NCH2CO2), 4.08 (q, J ) 7.0
Hz, 2H, OCH2), 5.67 (s, 2H, NH2), 6.25 (t, J ) 6.0 Hz, 1H,
NH); IR (KBr, cm-1) 3475 (NH2), 3375 (NH2), 1730 (CdO), 1645
(CdO).
1i
epalrestat
EBPC
71
291
a
b
IC50 value for rat lens AR. IC50 value for rat kidney ALR.
selectivity of EBPC was tested in the same conditions
as that for compounds described above. As summarized
in Table 3, the ratio of EBPC in enzyme selectivity was
291. From these results, it was found that the para-
banic acid moiety was the essential unit for AR selective
inhibitory activity.
Con clu sion
It was found that the parabanic acid moiety was
essential for AR selectivity and strong AR inhibitory
activity. In particular, 1c (NZ-314) showed strong
inhibitory activity against AR with extremely weak ALR
inhibition in vitro. These compounds are the first
examples of ARIs that have high AR selectivity. Studies
on the effect of the aryl part for enzyme selectivity are
in progress.
Eth yl 2,4,5-Tr ioxoim id a zolid in e-1-a ceta te (9). To a
suspension of the urea 7 (730 g, 5.0 mol) in THF (100 mL)
was added oxalyl chloride (515 mL, 6.0 mol) dropwise at 0 °C.
After vigorous stirring for 4 h at room temperature, the
precipitate was collected by filtration. The filtrate was
concentrated, and the residual solid was combined with the
precipitate obtained above. The solid was dissolved in MeOH
and filtered to remove the insoluble material. The filtrate was
concentrated, and the residue was recrystallized from EtOAc
Exp er im en ta l Section
Melting points (mp) were measured by a Yamato MP-21
melting point apparatus and are uncorrected. Proton nuclear
magnetic resonance (1H NMR) spectra were determined in
dimethyl sulfoxide-d6 on a Bruker AM-400 (400 MHz) spec-
trometer. Chemical shifts are reported in δ value from
internal tetramethylsilane. Splitting patterns are designated
as follows: s, singlet; d, doublet; t, triplet; q, quartet; br s,
broad singlet; and m, multiplet. Coupling constants are
reported in hertz (Hz). Infrared (IR) spectra were recorded
with a Hitachi 260-30 instrument. Mass spectra (MS) were
taken on a Hitachi M-80B mass spectrometer. Elemental
analyses (C, H, N) were carried out on a Perkin-Elmer 240C
element analyzer. Thin-layer chromatography (TLC) analyses
and chromatographic separations were performed with silica
gel 60 F254 plates (Merck Art. 5715) and silica gel 60 (Merck
Art. 7734; 70-230 mesh), respectively. Visualization was
accomplished with UV light and/or 10% phosphomolybdic acid
in ethanol. Unless otherwise noted, all commercially available
materials were used without further purification.
Gen er al P r ocedu r e for th e P r epar ation of Eth yl 3-(Ar y-
la lk yl)-2,4,5-tr ioxoim id a zolid in e-1-a ceta tes 5 (Sch em e 1).
Meth od A: 1-(3-Nitr oben zyl)u r ea (3c, n ) 1, X ) 3-NO2).
To a solution of 3-nitrobenzylamine hydrochloride (2c, n ) 1,
X ) 3-NO2; 47.2 g, 0.25 mol) and urea (60.0 g, 1.0 mol) in H2O
(100 mL) was added concentrated HCl (2 mL, 32 mmol), and
the mixture was refluxed for 3 h. The reaction mixture was
crystallized by standing at room temperature. The precipitate
was filtered and rinsed well with H2O. Recrystallization from
EtOH gave 3c as white crystals (47.2 g, 97%): mp 186-187
°C; 1H NMR δ 4.30 (d, J ) 6.2 Hz, 2H, CH2), 5.66 (s, 2H, NH2),
6.22 (t, J ) 6.2 Hz, 1H, NH), 7.62 (dd, J ) 8.8, 7.6 Hz, 1H,
Ar-H), 7.71 (d, J ) 7.6 Hz, 1H, Ar-H), 8.09 (d, J ) 8.8 Hz, 1H,
Ar-H), 8.10 (s, 1H, Ar-H); IR (KBr, cm-1) 3469 (NH2), 3319
(NH2), 1652 (CdO), 1585 (NO2), 1346 (NO2).
1
to give 9 as white crystals (850 g, 85%): mp 154-156 °C; H
NMR δ 1.21 (t, J ) 7.2 Hz, 3H, CH3), 4.16 (q, J ) 7.2 Hz, 2H,
OCH2), 4.34 (s, 2H, NCH2CO2), 12.40 (s, 1H, NH); IR (KBr,
cm-1) 1740 (CdO).
E t h yl 3-(2-Nit r ob en zyl)-2,4,5-t r ioxoim id a zolid in e-1-
a ceta te (5b). A solution of the parabanic acid 9 (10.0 g, 50
mmol) in DMF (50 mL) was added to a suspension of NaH (60
wt % in oil, 2.00 g, 50 mmol) in DMF (50 mL) with the
temperature maintained below 0 °C over a period of 30 min.
After stirring for 1 h, a solution of 2-nitrobenzyl bromide (10.8
g, 50 mmol) in DMF (50 mL) was slowly added at 0 °C. The
mixture was stirred for a further 2 h at 0 °C. The resulting
mixture was poured into ice-H2O containing concentrated HCl
(1 mL) to give a solid, which was filtered and washed well with
H2O and hexane. Recrystallization from EtOH gave 5b (12.5
g, 75%) as white crystals: mp 158.5-159.5 °C; 1H NMR δ 1.21
(t, J ) 7.1 Hz, 3H, CH3), 4.17 (q, J ) 7.0 Hz, 2H, OCH2), 4.43
(s, 2H, NCH2CO2), 5.11 (s, 2H, CH2Ar), 7.61 (ddd, J ) 8.2, 7.8,
1.3 Hz, 1H, Ar-H), 7.64 (dd, J ) 7.8, 1.3 Hz, 1H, Ar-H), 7.74
(ddd, J ) 7.8, 7.8, 1.2 Hz, 1H, Ar-H), 8.13 (dd, J ) 8.2, 1.2 Hz,
1H, Ar-H); IR (KBr, cm-1) 1738 (CdO), 1527 (NO2), 1336 (NO2);
MS m/ z 335 (M+). Anal. (C14H13N3O7) C, H, N.
Hyd r olysis of Ester s 5: 3-(3-Nitr oben zyl)-2,4,5-tr iox-
oim id a zolid in e-1-a cetic Acid (1c). A mixture of ethyl 3-(3-
nitrobenzyl)-2,4,5-trioxoimidazolidine-1-acetate (5c; 3.70 g,
11.0 mol), AcOH (10 mL), and concentrated HCl (5 mL) was
refluxed for 2.5 h. The reaction mixture was condensed under
reduced pressure to give a residue, which was refluxed again
with AcOH (10 mL) and concentrated HCl (5 mL) for another
2 h. The solid obtained by condensation was dissolved in
EtOAc, washed with H2O, and extracted with 10% aqueous
Na2CO3. The aqueous layer was washed with EtOAc and
acidified with concentrated HCl. The precipitated solid
was extracted with EtOAc, washed with H2O and brine, and
dried over anhydrous Na2SO4. Concentration followed by
1-(3-Nitr oben zyl)im id a zolid in e-2,4,5-tr ion e (4c, n ) 1,
X ) 3-NO2). To a suspension of 1-(3-nitrobenzyl)urea (3c, n
) 1, X ) 3-NO2; 19.5 g, 100 mmol) in THF (300 mL) was added
oxalyl chloride (10.2 mL, 120 mmol) dropwise at 0 °C. The
mixture was warmed to room temperature and stirred vigor-
ously for 3 h. After removal of the precipitate by filtration,
the filtrate was concentrated. The residual solid was dissolved
in EtOAc and washed with H2O and brine. The organic layer