Dual Action Inhibitors of AlDH
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 20 4019
Rea gen ts a n d Ch em ica ls. N-Hydroxyphthalimide, 1-hy-
droxysuccinimide, 1-hydroxybenzotriazole, benzenesulfonyl
chloride, ethyl chloroformate, pivaloyl chloride, benzoyl chlo-
ride, p-(diethylamino)benzoic acid, thionyl chloride, diethyl-
carbamoyl chloride, and sodium hydride were purchased from
Aldrich Chemical Co. (Milwaukee, WI). N-Carbethoxyl-O-
methyl-4-chlorobenzenesulfohydroxamic acid (5b) was pre-
pared as described.14 Yeast AlDH, NAD+, and glucose-6-
phosphate dehydrogenase were purchased from Sigma Chemical
Co. (St. Louis, MO).
Gen er a l P r oced u r e for th e P r ep a r a tion of 2-4. O-
(Diet h ylca r ba m oyl)-N-h yd r oxyp h t h a lim id e (4). N-Hy-
droxyphthalimide (48.9 g; 0.3 mol) was dissolved in 900 mL
of THF, and the solution was cooled in an ice bath under an
atmosphere of N2. Et3N (43.2 mL; 0.31 mol) was added over
ca. 10 min (red color). Diethylcarbamoyl chloride (38.0 mL;
0.30 mol) was added dropwise over 30 min. The ice bath was
then removed, and the reaction mixture was heated under
reflux for 4 h (red color faded to yellow). The reaction mixture
was allowed to cool to room temperature, EtOAc (500 mL) was
added, and the mixture was washed twice with 1 N HCl (100
mL), twice with 1 N NaHCO3 (100 mL, red color), and once
with water (100 mL). After drying, the solvents were removed
on a rotary evaporator in vacuo at 40 °C to give a colorless
solid (60.9 g; 77.4% yield; mp 121.5-122 °C) which was used
directly in the next reaction. An analytical sample, mp 126-
127 °C, was obtained by recrystallization from EtOAc; Rf )
0.95 (EtOAc:hexane, 2/1). 1H NMR: 7.74-7.88 (m, 4H, aryl-
H), 3.48 (q, 2H, J ) 6.9, CH2N), 3.37 (q, 2H, J ) 7.05, CH2N),
1.331 (t, 3H, J ) 6.81, CH3), 1.198 (t, 3H, J ) 6.96, CH3). 13C
NMR: 150.823 (CdO carbamate), 161.615 (CdO imide).
FTIR: (KBr) νCdO 1762; 1746 cm-1. Anal. (C13H14N2O4) C, H,
N.
colorless crystals; mp 71.5-72 °C; Rf ) 0.52 (toluene/EtOAc,
50:10). 1H NMR: 7.52-7.96 (m, 5H, aryl H), 9.00 (s, 1H, NH),
3.22 (q, 2H, CH2N, J ) 7.14), 3.11 (q, 2H, CH2N, J ) 7.08),
1.11 (t, 3H, CH3, J ) 7.14), 0.88 (t, 3H, CH3, J ) 7.08). FTIR:
νCdO 1727 cm-1. Anal. (C11H16N2O4S) C,H,N,S.
Gen er a l P r oced u r e for th e P r ep a r a tion of Com p ou n d s
1a -d . N-Ben zoyl-O-(d iet h ylca r b a m oyl)b en zen esu lfo-
h yd r oxa m ic Acid (1c). Et3N (408 µL; 2.93 mmol) was added
to a solution of 7 (723 mg; 2.66 mmol) and benzoyl chloride
(340 µL; 2.93 mmol) dissolved in 27 mL of CH2Cl2. The reaction
mixture was stirred at room temperature for 24 h at which
time TLC (toluene/EtOAc, 50:10) showed complete reaction of
7 (Rf ) 0.52). The reaction mixture was evaporated to dryness
and the residue was flash chromatographed using toluene/
EtOAc (50:10) as eluant to give 700 mg (70% yield) of a
colorless oil which crystallized on standing at 0 °C. Recrys-
tallization from toluene-hexane gave 1c as colorless crystals;
mp 71-72 °C; Rf ) 0.70 (toluene/EtOAc, 50:10). 1H NMR:
7.35-8.11 (m, 10H, aryl H), 3.23 (brd q, 4H, J ) 6.93), 1.04
(brd t, 6H, J ) 6.93). FTIR: (KBr) νCdO 1763, 1697 cm-1. Anal.
(C18H20N2O7S) C,H,N,S.
N -Ac e t y l -O -( d i e t h y l c a r b a m o y l ) b e n z e n e s u l f o -
h yd r oxa m ic Acid (1a ). This compound was prepared using
acetic anhydride as described above for 1c. Colorless solid; mp
93-94 °C (benzene-hexane); 58.4% yield; Rf ) 0.57 (hexanes-
EtOAc, 2:1). 1H NMR: 7.52-8.05 (m, aryl-H, 5H), 3.36 (q, 4H,
J ) 7.11, (CH2)2), 2.12 (s, 3H, CH3CO), 1.234 (t, 3H, J ) 7.11,
CH3), 1.164 (t, 3H, J ) 7.11, CH3). FTIR: (KBr) νCdO 1708,
1768 cm-1. Anal. (C13H18N2O5S) C,H,N,S.
N -P i v a lo y l-O -(d i e t h y lc a r b a m o y l)b e n z e n e s u lfo -
h yd r oxa m ic Acid (1b). Prepared as described above for 1c
except that pivaloyl chloride was used. Colorless solid; mp
110-111 °C (toluene-hexane); 60.1% yield; Rf ) 0.56 (toluene-
EtOAc, 50:5). 1H NMR: 7.51-8.16 (m, 5H, aryl-H), 3.46 (dq,
4H, J ) 7.20, 2(CH2N)), 1.33 (t, 3H, J ) 7.20, CH3 carbamate),
1.23 (J ) 7.31, t, 3H, CH3 carbamate), 1.18 (s, 9H, (CH3)3.
FTIR: (KBr) νCdO 1754, 1694 cm-1. Anal. (C14H20N2O7S)
C,H,N,S.
O-(Dieth ylca r ba m oyl)-1-h yd r oxysu ccin im id e (3). Pre-
pared from 1-hydroxysuccinimide as described above for 4.
Colorless solid (57% yield); mp 109-111 °C (recrystallized from
1
EtOAc-hexane); Rf ) 0.27 (hexane:THF, 3:1). H NMR: 3.40
(q, J ) 8 Hz, 4H), 2.80 (s, 4H), 1.23 (t, J ) 8 Hz, 6H). FTIR:
(KBr) νCdO 1756, 1745 cm-1. Anal. (C9H14N2O4) C, H, N.
N-(E t h oxyca r b on yl)-O-(d iet h ylca r b a m oyl)b en zen e-
su lfoh yd r oxa m ic Acid (1d ). Prepared as described above for
1c except that ethyl chloroformate was used. Colorless oil
obtained by flash chromatography using toluene/EtOAc (50:
10) as eluant; 83.2% yield; Rf ) 0.68 (toluene/ETOAc, 50:10),
Rf ) 0.71 (toluene/EtOAc/Et3N, 50:10:1), Rf ) 0.55 (toluene/
O-(Dieth ylca r ba m oyl)-1-h yd r oxyben zotr ia zole (2). Pre-
pared from 1-hydroxybenzotriazole as described above for 4.
Colorless solid (81.6% yield); mp 71-72 °C (recrystallized from
EtOAc-hexane); Rf ) 0.48 (hexane:THF, 3/1). 1H NMR: 8.17-
7.83 and 7.57-7.13 (2m, 4H), 3.52 (vbrm, 4H), 1.32 (vbrm, 6H).
FTIR: (KBr) νCdO 1769 cm-1. Anal. (C11H14N2O4) C,H,N.
1
EtOAc/AcOH, 50:10:2). H NMR: 7.52-8.10 (m, 5H, aryl H),
4.17 (q, 2H, J ) 7.00, CH2O), 3.37 (q, 4H, J ) 6.95, CH2N),
1.19 (t, 3H, J ) 7.01, CH3), 1.25 (brd t, 6H, 2CH3). 13C NMR:
151.73 (CdO, carbamate), 149.513 (CdO, carbethoxy). FTIR:
(KBr) νCdO 1759, 1759 cm-1. λmax (EtOH): 224.5 nm (ꢀ 12 200).
Anal. (C14H20N2O6S) C,H,N,S.
O-(Dieth ylca r ba m oyl)h yd r oxyla m in e (6). O-(Dieth yl-
ca r ba m oyl)ben zen esu lfoh yd r oxa m ic Acid (7). Compound
4 (2.62 g; 10 mmol) was dissolved in 100 mL of acetonitrile.
The reaction vessel was flushed with N2 for 5 min, and
anhydrous N2H2 (3.3 equiv; 1.06 mL; 33 mmol) was added.
Caution: Anhydrous N2H2 should be stored and handled under
N2. A white solid formed in a pale-yellow liquid suspension.
The mixture was stirred at room temperature for 30 min and
then allowed to stand in an ice bath for 3 h. TLC (toluene/
EtOAc, 50:10) showed that the reaction was complete. The
precipitate was collected and washed twice with 20 mL of ice-
cold CH3CN. [This precipitate, the hydrazine salt of phthal-
hydrazide, weighed 1.92 g (99% yield) after drying in vacuo.]
The CH3CN filtrate was cooled in an ice bath, and 30% w/w
H2O2 (2.66 mL, 10.3 mmol) was added in four portions over 5
min when gas evolution ensued. After 1 h of stirring, at which
point gas evolution had stopped and tests for H2O2 (iodide-
starch paper) and N2H2 (salicylaldehyde/yellow fluorescence
under long-wave UV light) were negative, NaHCO3 (840 mg,
10 mmol) was added, followed by benzenesulfonyl chloride
(1.28 mL, 10 mmol), and the reaction mixture was allowed to
proceed at room temperature overnight. TLC at this time
showed almost complete loss of 6 (Rf ) 0.30; EtOAc/hexane,
1:2) and formation of 7 (Rf ) 0.56; EtOAc/hexane, 1:2). The
mixture was diluted with 5 volumes of saturated NaCl and
extracted three times with ether, and the combined ether
extracts were washed once with saturated NaCl, dried, and
evaporated to dryness to give 7 (2.68 g, 98.5% yield) as a
slightly yellow oil. Crystallization from toluene-hexane gave
N-(E t h oxyca r b on yl)-O-m e t h ylb e n ze n e su lfoh yd r ox-
a m ic Acid (5a ). Prepared from O-methylbenzenesulfohydrox-
amic acid24 using the method described for 5b.13 This com-
pound was purified by flash chromatography (silica gel 60)
using toluene/EtOAc (50:10) as eluant (18.3% yield, colorless
1
oil); Rf ) 0.65 (toluene/EtOAc, 50:10). H NMR: 7.506-8.011
(m, 5H, aryl H), 4.21 (q, J ) 7.11, 2H, CH2), 4.02 (s, 3H, OCH3),
1.25 (t, J ) 7.14, 3H, CH3). FTIR: (KBr) νCdO 1751.6 cm-1
Anal. (C10H13NO3S) C,H,N,S.
.
N-(N,N-Dieth ylca r ba m oyl)-O-m eth ylben zen esu lfoh y-
d r oxa m ic Acid (5c). O-Methylbenzenesulfohydroxamic acid
(1.87 g; 10 mmol) was dissolved in 10 mL of dry dimethylac-
etamide in an oven-dried three-necked 25-mL flask, equipped
with a magnetic stirrer and a bubbler-guarded water-cooled
condenser. A N2 atmosphere was established in the flask.
Under slow N2 flow, solid NaH (368 mg; 15.3 mmol) was added
all at once. The flask was resealed and stirred at room
temperature for 2 h at which time the flask contained a cream-
colored slurry. Diethylcarbamoyl chloride (1.94 mL; 15.3 mmol)
was added, and the reaction mixture was warmed and stirred
at 40 °C (water bath) for 19 h. The reaction mixture was then
diluted with 100 mL of saturated NaCl and extracted with
ether (4 × 16 mL). The combined ether extracts were washed
with saturated NaCl, and the organic layer was dried and