1734
Can. J. Chem. Vol. 83, 2005
added, and the product began to slowly precipitate. The re-
action was stirred for a further 20 min at 40 °C and then
cooled to room temperature over 15 min while stirring was
continued. The suspension was then placed at 4 °C, the off-
white crystals were collected by filtration, and rinsed with
50 mL of cold water to yield 17.65 g (83%) of the title com-
DMSO, ppm) δ: 11.79 (s, 1H), 8.59 (s, 1H), 4.53 (s, 2H),
3.71 (s, 3H), 1.40 (s, 9H). 13C NMR (100 MHz, CHCl3,
ppm) δ: 165.6, 163.2, 158.8, 152.3, 149.6, 105.3, 84.1, 52.5,
49.9, 28.0. HR-MS (EI) calcd. for C12H16N2O6: 284.1009;
found: 284.1009.
1
pound; mp 302–304 °C. H NMR (400 MHz, DMSO, ppm)
(Uracil-5-methylcarboxylate-1-yl)acetic acid (12)
δ: 11.89 (s, 1H), 11.49 (s, 1H), 9.72 (s, 1H), 8.12 (s, 1H).
13C NMR (100 MHz, DMSO, ppm) δ: 186.8, 162.6, 150.6,
149.4, 110.2.
Compound 11 (1.61 g, 5.66 mmol) and Et3SiH (0.75 mL,
4.70 mmol) were suspended in 20 mL DCM, cooled to 0 °C,
and 15 mL of TFA was added dropwise. The reaction was
stirred for 1 h on ice and an additional 2.5 h at room temper-
ature. The mixture was evaporated to dryness in vacuo and
the remaining volatiles were removed by co-evaporation
with CH2Cl2 and diethyl ether. The compound was triturated
with a mixture of approximately 5 mL of CH2Cl2 and 80 mL
of diethyl ether and cooled to 0 °C overnight. Filtration and
drying under vacuum gave 1.22 g (94%) of a white solid.
TLC (EtOAc–MeOH–AcOH, 80:15:5): Rf 0.16; mp 227–
Uracil-5-carboxylic acid (9)
5-Formyluracil (4.30 g, 30.70 mmol) was dissolved in
350 mL of water by heating to reflux. To this solution was
added K2S2O8 (8.30 g, 30.70 mmol) and AgNO3 (50 mg,
0.29 mmol), and the reaction was stirred while cooling to
65 °C over 30 min. A precipitate formed upon concentrating
the volume to 50 mL. This mixture was cooled to 4 °C to
promote the precipitation, and the product was subsequently
collected by filtration. The title compound was purified by
suspending it in 125 mL of water, adding 4 mol/L NaOH un-
til a clear solution was obtained, and reprecipitating the
compound by dropwise addition of concd. HCl until pH 2.0.
Cooling the mixture to 4 °C followed by filtration yielded
1
229 °C. H NMR (400 MHz, DMSO, ppm) δ: 11.68 (s, 1H),
8.59 (s, 1H), 4.55 (s, 2H), 3.70 (s, 3H). 13C NMR
(100 MHz, CHCl3, ppm) δ: 169.2, 163.0, 159.5, 153.4,
150.2, 103.4, 51.6, 49.2. HR-MS (EI) calcd. for C12H8N2O6:
228.0382; found: 228.0375.
1
3.34 g (70%) of a white solid; mp (dec.) 286–288 °C. H
tert-Butyl N-[2-Fmoc-aminoethyl]-N-[(uracil-5-
NMR (400 MHz, DMSO, ppm) δ: 12.73 (s, 1H), 11.99 (s,
2H), 8.25 (s, 1H). 13C NMR (100 MHz, DMSO, ppm) δ:
165.2, 163.5, 150.4, 150.2, 101.2.
methylcarboxylate-1-yl)acetyl]glycinate (13)
Compound 12 (0.210 g, 0.92 mmol), HOBt hydrate
(0.141 g, 0.92 mmol), and DCC (0.190 g, 0.92 mmol) were
dissolved in 3 mL of DMF and stirred under nitrogen for
15 min. The free amine form of the Fmoc-backbone tert-
butyl ester (0.365 g, 0.92 mmol) was dissolved in a minimal
amount of DMF and added to the mixture along with
Hünings base (0.169 mL, 0.97 mmol). The reaction was
stirred for 24 h at room temperature and extracted with
EtOAc, sodium bicarbonate, phosphate buffer (pH ~ 4.5),
and brine. The combined organic phases were dried
(Na2SO4), filtered, and concentrated in vacuo. The solid was
purified by flash chromatography (DCM–MeOH gradient) to
yield 0.298 g (55%) of a white solid. TLC (EtOAc–MeOH,
Uracil-5-methylcarboxylate (10)
Uracil-5-carboxylic acid (2.50 g, 16.00 mmol) was sus-
pended in methanol (150 mL) and HCl gas was bubbled into
the suspension. The HCl was generated by the dropwise
combination of 40 mL of concd. H2SO4 and 40 mL of
concd. HCl. Once the mixture was saturated with HCl, it
was refluxed for 12 h and then the solvent was removed in
vacuo. The product was then recystallized from methanol to
yield 2.34 g (86%) of a white solid. TLC (EtOAc–MeOH,
90:10): Rf 0.52; mp (dec.) 267 to 268 °C. 1H NMR
(400 MHz, DMSO, ppm) δ: 11.61 (s, 1H), 11.31 (s, 1H),
8.12 (s, 1H), 3.67 (s, 3H). 13C NMR (100 MHz, DMSO,
ppm) δ: 163.2, 160.1, 150.6, 149.7, 102.9, 51.4. HR-MS
(EI) calcd. for C6H6N2O4: 170.0328; found: 170.0324.
1
90:10): Rf 0.67; mp (dec.) 135–137 °C. H NMR (400 MHz,
DMSO, ppm) δ: 8.43 (s, ma., 0.6H), 8.34 (s, mi., 0.4H),
7.89 (d, 2H, J = 7.4 Hz), 7.68 (m, 2H), 7.40 (t, 2H, J =
7.4 Hz), 7.32 (t, 2H, J = 7.4 Hz), 7.24 (m, 1H), 4.85 (s, ma.,
1.2H) and 4.86 (s, mi., 0.8H), 4.34–4.16 (m) and 3.98 (s,
ma.) (5H), 3.68 (s, 3H), 3.28–3.02 (m, 4H). 13C NMR
(100 MHz, DMSO, ppm) δ: 167.9, 166.8, 163.0, 159.5,
156.1, 153.7, 150.1, 143.9, 140.8, 127.6, 127.1, 125.1,
120.1, 103.2, 81.0, 65.5, 51.5, 50.0, 48.8, 48.3, 46.7, 27.7.
HR-MS (ESI-TOF) calcd. for sodium adduct C31H34N4O9Na:
629.2225; found: 629.2254.
tert-Butyl (uracil-5-methylcarboxylate-1-yl)acetate (11)
Uracil-5-methylcarboxylate (2.06 g, 12.11 mmol) was dis-
solved in dry DMF (40 mL), and K2CO3 (1.67 g,
12.11 mmol) was added. tert-Butyl bromoacetate (1.79 mL,
12.11 mmol) was added dropwise to the stirred mixture and
stirring was continued for 24 h while the reaction mixture
was kept under an atmosphere of nitrogen. The reaction mix-
ture was filtered to remove the undissolved potassium car-
bonate and then the solvent was removed in vacuo. The
residue was extracted with ethyl acetate (3 × 75 mL) and
water (25 mL). The combined organic layers were then
washed with brine, dried (Na2SO4), filtered, and concen-
trated in vacuo. The crude product was recrystallized from
methanol to yield 2.14 g (62%) of a white solid. TLC
(EtOAc–MeOH, 90:10): Rf 0.71; mp 179 to 180 °C. 1H
NMR (400 MHz, CHCl3, ppm) δ: 8.69 (s, 1H), 8.19 (s, 1H),
N-[2-Fmoc-aminoethyl]-N-[(uracil-5-methylcarboxylate-
1-yl)acetyl]glycine (14)
Compound 13 (0.250 g, 0.41 mmol) and Et3SiH (59.0 uL,
0.37 mmol) were suspended in 2 mL DCM, cooled to 0 °C,
3 mL of TFA was added dropwise, and the reaction was
stirred for 1 h in an ice bath and 2.0 h at room temperature.
The mixture was evaporated to dryness in vacuo and the re-
maining volatiles were removed by co-evaporation sequen-
tially with CH2Cl2 and diethyl ether. The solid was slurried
in CH2Cl2–diethyl ether, cooled to 0 °C for 12 h, and subse-
1
4.43 (s, 2H), 3.86 (s, 3H), 1.47 (s, 9H). H NMR (400 MHz,
© 2005 NRC Canada