5810 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 18
Strassmaier et al.
mL of ethanol was refluxed for 72 h. Reaction progress was
followed by TLC. Removal of solvent in vacuo gave a residue
that was purified on a silica gel column; 175 mg (35%) of
starting material and 145 mg (45%) of 2 were sequentially
eluted with 2-propanol/acetic acid/water (5:3:2). 1H NMR (400
MHz, CD3OD) δ 7.78 (d, J ) 9 Hz, 2H), 6.59 (d, J ) 9 Hz, 2H),
4.91 (s, 1H, NH), 4.70 (br s, 2H), 3.78-3.80 (m, 2H), 3.41-
3.44 (m, 2H), 3.20 (s, 6H), 3.14 (t, J ) 7 Hz, 2H), 1.91 (s, 3H,
CH3COO-), 1.75-1.81 (m, 2H), 1.58-1.64 (m, 2H), 1.34-1.47
(m, 4H), 0.98 (t, J ) 7.5 Hz, 3H), 0.97 (t, J ) 7.5 Hz, 3H) (peak
assignments were aided by 1H-1H COSY experiment); 13C
NMR (125 MHz, CD3OD) δ 179.4 (CH3COO-), 167.7, 155.4,
132.9, 116.3, 112.3, 66.5, 64.1, 58.5, 52.2, 43.7, 32.4, 25.7, 23.8
(CH3COO-), 21.4, 20.9, 14.4, 14.0; MS (ESI) m/z 321.3 (M)+.
3-Amino-N-(2-{[4-(butylamino)benzoyl]oxy}ethyl)-N,N-
dimethylpropan-1-aminium Acetate (3). A mixture of
tetracaine (1) (2.5 g, 9.46 mmol) and 3-bromopropylamine
hydrochloride (2.1 g, 10 mmol) in 20 mL of ethanol was
refluxed for 8 h. Reaction progress was followed by TLC.
Removal of solvent in vacuo gave a residue that was purified
by ion-exchange HPLC. Unreacted tetracaine (1) eluted first,
compound 3 eluted second, followed by 4 in the ratio 67:27:6
(peak areas monitored at 312 nm). Compound 3 was further
purified by RP-HPLC and dried repeatedly in a Speed-Vac
(Savant). 1H NMR (500 MHz, CD3OD) δ 7.79 (d, J ) 9 Hz,
2H), 6.60 (d, J ) 9 Hz, 2H), 4.94 (s, 3H, NH), 4.73 (br s, 2H),
3.83-3.85 (m, 2H), 3.55-3.58 (m, 2H), 3.25 (s, 6H), 3.15 (t, J
) 7 Hz, 2H), 2.96 (t, J ) 7 Hz, 2H), 2.15-2.21 (m, 2H), 1.91
(s, 3H, CH3COO-), 1.58-1.65 (m, 2H), 1.41-1.48 (m, 2H), 0.98
(t, J ) 7 Hz, 3H) (peak assignments were aided by 1H-1H
COSY experiment); 13C NMR (125 MHz, CD3OD) δ 179.4
(CH3COO-), 167.7, 155.42, 132.9, 116.3, 112.3, 64.7, 63.7, 58.5,
52.3, 43.8, 37.9, 32.4, 24.1 (CH3COO-), 23.1, 21.4, 14.4;
MALDI-MS (R-cyano-4-hydroxycinnamic acid matrix) m/z
322.23 (M)+.
N-[4-(Acetylamino)butyl]-N-(4-bromophenyl)aceta-
mide (9). Et3N (16.2 g, 0.16 mol) and acetic anhydride (14.2
g, 0.139 mol) were added to a solution of 8 (14.4 g, 0.04 mol)
in CH2Cl2 (200 mL) with stirring under N2. After 8 h the
reaction was quenched with 1 N NaOH (200 mL) and extracted
with CH2Cl2 (3 × 100 mL). The solvent was evaporated in
vacuo, yielding a viscous yellow oil that was purified on a silica
gel column eluted with CH3CN/H2O/AcOH (80:5:15). Final
yield was 13.07 g (99%) of 9. 1H NMR (300 MHz, CDCl3) δ
7.55 (d, J ) 9 Hz, 2H), 7.05 (d, J ) 9 Hz, 2H), 6.26 (s, 1H),
3.67 (t, J ) 6.6 Hz, 2H), 3.23 (br q, 2H), 1.98 (s, 3H), 1.86 (s,
3H), 1.55 (m, 4H); 13C NMR (75 MHz, CDCl3) δ 170.1, 141.8,
132.9, 129.6, 121.7, 48.4, 39.1, 26.1, 25.1, 23.1, 22.7; GC-MS
m/z 327 (MH)+.
N-[4-(Acetylamino)butyl]-N-(4-cyanophenyl)aceta-
mide (10). A solution of 9 (12.2 g, 0.037 mol) and CuCN (4.12
g, 0.046 mol) in dry N-methyl-pyrrolidinane (50 mL) was
heated to 200 °C for 1.5 h. The reaction was quenched at room
temperature with concentrated NH3 (120 mL) and extracted
with CH2Cl2 (3 × 100 mL). The combined extracts were dried
(Na2SO4) and evaporated in vacuo to give a dark brown oil,
which was purified on a silica gel column. Elution with EtOAc/
isopropyl alcohol (IPA) (9:1) yielded 9.0 g (89% yield) of 10 as
1
a pale yellow oil. H NMR (300 MHz, CDCl3) δ 7.76 (d, J ) 9
Hz, 2H), 7.35 (d, J ) 9 Hz, 2H), 6.17 (s, 1H), 3.75 (br t, 2H),
3.23 (br q, 2H) 1.98 (s, 3H), 1.90 (s, 3H), 1.55 (m, 4H); 13C NMR
(75 MHz, CDCl3) δ 170.1, 169.6, 146.8, 133.7, 128.7, 111.7,
48.7, 39.0, 26.2, 25.2, 23.1, 22.7; GC-MS m/z 274 (MH)+.
4-[(4-Aminobutyl)amino]benzoic Acid (11). A solution
of 10 (7.0 g, 0.026 mol) in HBr (80 mL) was heated under reflux
for 4 h. HBr was removed in vacuo, and silica gel and H2O
were added. Volatiles were removed in vacuo and the silica
gel mixture was applied to the top of a silica gel column and
eluted with CH3CN/H2O/NH3 (60:40:10) to give pure 11 (4.9
1
g, 85% yield). H NMR (300 MHz, D2O) δ 7.39 (d, J ) 9 Hz,
2H), 6.42 (d, J ) 9 Hz, 2H), 2.66 (t, J ) 6.5 Hz, 2H), 2.15 (t,
J ) 6.4 Hz, 2H), 0.98-1.20 (m, 4H); 13C NMR (75 MHz, D2O)
δ 178.0, 153.8, 133.4, 127.2, 115.1, 45.6, 42.8, 31.9, 28.1; GC-
MS m/z 209 (MH)+.
3-[(3-Aminopropyl)amino]-N-(2-{[4-(butylamino)-
benzoyl]oxy}ethyl)-N,N-dimethylpropan-1-aminium Ac-
etate (4). See ref 23 for this procedure.
N-(4-Bromophenyl)succinamide (7). To a solution of
succinamic acid (5) (18.05 g, 0.154 mol) in dry DMF (130 mL)
was added N,N′-carbonyldiimidazole (25 g, 0.154 mol) with
stirring at room temperature under N2. After evolution of CO2
was complete (2 h), p-bromoaniline (6) (26.4 g, 0.154 mol) was
added and the reaction proceeded for an additional 24 h. The
mixture was concentrated in vacuo to a brown solid and
washed with H2O followed by CCl4. Recrystallization from
EtOAc and EtOH yielded a white crystalline product (7) (25
4-[[(Benzyloxy)carbonyl](4-{[(benzyloxy)carbonyl]-
amino}butyl)amino]benzoic Acid (12). Benzyl chlorofor-
mate (5.2 g, 0.31 mol) was added dropwise at 0 °C to a solution
of 11 (4.84 g, 0.022 mol) in sodium phosphate buffer (pH 12,
176 mL). The reaction proceeded at room temperature for 24
h, yielding a mixture of benzyloxycarbonyl (Cbz) adducts. The
mixture was acidified with HCl and extracted with CH2Cl2 (3
× 25 mL), and the extracts were evaporated under reduced
pressure. The resulting crystalline material was stirred in 1
M KOH (44 mL) and dioxane (100 mL) until a single product
was detected with TLC. The solution was acidified with HCl
to pH < 1, extracted with CH2Cl2 (3 × 25 mL), dried (Na2-
SO4), and evaporated under reduced pressure. The resulting
oil was purified on a silica gel column; elution with hexane/
EtOAc (1:1) gave 12 as a white crystalline solid (7 g, 68% yield).
1H NMR (300 MHz, CDCl3) δ 7.79 (d, J ) 9 Hz, 2H), 7.25 (m,
12H), 6.50 (s, 1H), 5.13 (s, 2H), 5.05 (s, 2H), 3.70 (br t, 2H),
3.10 (br q, 2H), 1.55 (m, 4H); 13C NMR (75 MHz, CDCl3) δ
169.0, 156.4, 155.0, 144.8, 136.5, 136.2, 131.3, 128.3, 128.0,
127.7, 126.7, 67.5, 66.5, 49.6, 41.0, 26.9, 25.5.
1
g, 60% yield). H NMR (300 MHz, DMSO-d6) δ 10.1 (s, 1H),
7.6 (d, J ) 9 Hz, 2H), 7.4 (d, J ) 9 Hz, 2H), 7.3 (s, 1H), 6.7 (s,
1H), 2.5 (t, J ) 6.5 Hz, 2H), 2.37 (t, J ) 6.4 Hz, 2H); 13C NMR
(75 MHz, DMSO-d6) δ 173.3, 170.8, 138.7, 131.4, 120.8, 114.3,
31.5, 29.8; GC-MS m/z 271 (MH)+.
N-(4-Bromophenyl)butane-1,4-diamine (8). Borane di-
methyl sulfide (26 g, 0.342 mol) was added dropwise over 0.5
h at 0 °C to a three-neck 250 mL round-bottom flask charged
with 7 (23.4 g, 0.086 mol) in dry tetrahydrofuran (THF) and
equipped with a pressure-equalizing addition funnel, ther-
mometer, and reflux condenser. The mixture was refluxed at
45 °C for 3 h and cooled to 25 °C, and MeOH (41 mL) was
added dropwise. After the mixture was cooled to 5-10 °C,
anhydrous HCl was bubbled in until pH 1.5-2.0 was reached.
The resulting slurry was refluxed with the addition of MeOH
(2 × 75 mL) until the precipitate had dissolved. The solvent
was removed in vacuo; the resulting white solid was dissolved
in H2O (200 mL), and NaOH (∼3.5 g) was added until pH 11.5
was reached. The mixture was extracted with CH2Cl2, dried
(Na2SO4), evaporated in vacuo, and 18 g (58% yield) of 8 was
purified on a silica gel column (CH3CN/H2O/AcOH 80:16:5).
1H NMR (300 MHz, CDCl3) δ 8.0 (s, 1H), 7.21 (d, J ) 9 Hz,
2H), 6.45 (d, J ) 9 Hz, 2H), 3.25 (t, J ) 6.5 Hz, 2H), 2.85 (t,
J ) 6.4 Hz, 2H), 1.95 (s, 3H), 1.75 (m, 2H), 1.6 (m, 2H); 13C
NMR (75 MHz, CDCl3) δ 177.8, 147.2, 131.8, 114.2, 108.6, 43.0,
39.2, 26.0, 25.3, 23.1; GC-MS m/z 243 (MH)+.
2-(Dimethylamino)ethyl 4-[[(Benzyloxy)carbonyl](4-
{[(benzyloxy)carbonyl]amino}butyl)amino]benzoate (13).
N,N′-Carbonyldiimidazole (1.18 g, 7 mmol) was added to a
solution of 12 (3.1 g, 6.6 mmol) in dry glyme (40 mL) under
N2. The reaction was heated to just below boiling for 2 h,
followed by the addition of 2-(dimethylamino)ethanol (1.77 g,
0.02 mol) and NaH (∼2 mg). After 8 h the reaction was
complete as judged by TLC. The solvent was removed in vacuo
and the resulting residue was dissolved in CCl4 (50 mL). After
extraction with H2O (3 × 30 mL), the organic phase was dried
over Na2SO4 and the solvent was evaporated under reduced
pressure. The resulting oil was purified on a silica gel column
eluted with EtOAc/IPA (9:1), yielding pure 13 as a yellowish
1
gum (3.3 g, 92% yield). H NMR (300 MHz, CDCl3) δ 8.05 (d,
J ) 9 Hz, 2H), 7.31 (m, 12H), 5.15 (s, 2H), 5.07 (s, 2H), 4.78