814 J . Org. Chem., Vol. 67, No. 3, 2002
Ryberg and Matsson
HPLC, a Phenomenex spherisorb 10 ODS(2) 250 × 10 mm i.d.
C18 column was used. Data collection and HPLC control were
performed with the use of a Beckman System Gold chroma-
tography software package.
Sample injection and fraction collection were performed by
a Gilson 231 XL sampling injector in combination with a Gilson
401C dilutor.
was dried over MgSO4, a small amount of silica was added to
the solution. The CH2Cl2 was evaporated off and the silica was
applied to a column prepacked with silica. The product was
eluted with Et2O/pentane 1:1, and 150 mg 75% of product was
obtained.
4-H yd r oxy-4-(4′-n it r op h e n yl)-(1,1,1,3,3-2H 5)b u t a n -2-
on e Eth ylen e Aceta l (6). 1,2-Ethanediol (5.4 g, 87 mmol),
D2O (2 mL), and pyridinium p-toluenesulfonate (0.5 g) were
weighed into a round-bottomed flask equipped with a Dean-
Stark water separator. Benzene (75 mL) was added, and the
mixture was refluxed until no more water separated. Another
2 mL of D2O was added, and the procedure was repeated. In
total, seven 2 mL portions of D2O were added. Then 4-hydroxy-
4-(4′-nitrophenyl)-(1,1,1,3,3-2H5)butan-2-one (2.4 g, 11.2 mmol)
was added and the mixture was refluxed until no more water
separated (2 h). The benzene was removed in vacuo, and
diethyl ether (100 mL) was added to the brownish residue.
This ethereal solution was washed with saturated aqueous
NaHCO3 (50 mL) and H2O (50 mL) and dried over MgSO4.
Removal of the ether in vacuo yielded a brown oil. The product
was purified by chromatography on silica using diethyl ether/
pentane/triethylamine 100:50:1 as eluent. A 1.53 g (53%)
Liquid scintillation counting was performed with a Beckman
LS 6000 LL liquid scintillation counter in wide open mode,
using Zinsser quicksafe A as scintillation cocktail in Zinsser
20 mL poly vials.
1H and 13C NMR spectra were recorded on a Varian Unity
400 MHz spectrometer at 400 and 100.6 MHz, respectively,
with chloroform-d1 as internal standard.
Kin etic P r oced u r e. The kinetic experiments were run
under pseudo-first-order conditions. HPLC system 4.6 × 250
mm Phenomenex C-18 column, solvent system methanol/
50mM ammoniumformate pH 3.5, 0-9 min 55% methanol,
9-10 min 55-95% methanol, 14-15 min 95-55% methanol
1 mL/min. In this system, the reactant eluted at tR ) 8.1 min
and the product eluted at tR ) 10.5 min, and they were baseline
separated for 1.4 min.
1
The method for determining the F KIEs was identical to
the one used for determination of the F KIEs on protic
substrate.3
portion of 6 was obtained. H NMR: 3.95-4.12 (m, 4H), 4.27
(s, 1H), 5.09 (s, 1H), 7.5-8.2 (m, 4H). 13C: 64.3, 64.8, 69.5,
123.6, 126.4, 147.5, 151.8.
Levelin g of th e Deu ter iu m Con ten t in th e 18F a n d 19F
Su bstr a tes. The deuterated 18F and 19F[14C] substrates were
dissolved in 0.4 mL of CD3OD, and 0.4 mL 1 M imidazole in
(D2O) pH 6.9 was added. The mixture was kept at 38 °C until
50% conversion (30-40 min). Then the mixture was injected
on the HPLC (10 × 250 mm C-18 4 mL/min, 55% methanol/
45% 50mM ammonium formate pH 3.5), and the fraction
containing unreacted starting material was collected. The
collected fraction (4 mL) was diluted with 6 mL of H2O and
passed through a 500 mg C-18 SPE column. The column was
washed with 2 mL of H2O and then eluted with 2 mL of
acetonitrile. The eluate was concentrated in vacuo and redis-
solved in 0.5 mL 50% aquous methanol.
4-Tolu en esu lfoxy-4-(4′-n itr oph en yl)-(1,1,1,3,3-2H5)bu tan -
2-on e Eth ylen e Aceta l (7). 4-Hydroxy-4-(4′-nitrophenyl)-
(1,1,1,3,3-2H5)butan-2-one ethyl acetal (800 mg, 3.1 mmol),
p-toluenesulfonyl chloride (900 mg, 4.7 mmol), N,N-(dimethy-
lamino)pyridine (390 mg, 3.2 mmol), and triethylamine (0.55
mL, 3.2 mmol) were stirred in dichloromethane (10 mL) for
30 h. The mixture was diluted with diethyl ether (60 mL) and
filtered. The etheral extract was washed with saturated
aqueous NaHCO3 and saturated aqueous NaCl and dried over
MgSO4. The product was purified by chromatography on silica
using diethyl ether/pentane/triethylamine 80:20:2 as eluent.
1
Yield: 0.4 g, 32%. H NMR δ: 2.35 (s, 3H), 3.8-3.92 (m, 4H),
5.75 (s, 1H), 7.1-7.5 (m, 4H), 7.3-8.06 (m, 4H). 13C: 21.5, 64.4,
79.1, 123.5, 127.6, 127.7, 129.4, 133.9, 144.8, 146.1, 147.5.
4-[18F ]F lu or o-4-(4′-n itr op h en yl)-(1,1,1,3,3-2H5)bu ta n -2-
on e. The aqueous [18F]F- solution (1-2 GBq, 0.5-1 mL) was
added to K2CO3 (1.5-2 mg) and Kryptofix(2.2.2) (3-4 mg) in
a 3 mL septum-covered vial. The water was removed by
repeated azeotropic evaporation with acetonitrile under a flow
of nitrogen at 100 °C. When the vial was completely dry, the
nitrogen flow was stopped and compound 7 (3 mg) dissolved
in deuterated acetonitrile (0.2 mL) was added. The resulting
violet solution was kept at 80-90 °C for 30 min and then cooled
to 70 °C. Then p-TsOD in D2O/acetone-d6 1:5 20 mg/mL (0.5
mL) was added, and the mixture was kept at 70 °C for 10 min.
The mixture was cooled, H2O (0.5 mL) was added, and the
solution was injected to a semipreparative Phenomenex C-18
HPLC column. Eluent system: acetonitrile, 50 mM ammonium
formate pH 3.5, 4 mL/min. gradient 0-2 min 10% acetonitrile,
2-21 min 10-65% acetonitrile. The fraction between tR 17.6-
19.2 was collected. The collected fraction was diluted with H2O
(10 mL) and passed through a Supelco Supelclean ENVI-18
SPE column. The column was washed with H2O (3 mL) and
then eluted with acetonitrile (2 mL). The acetonitrile was
removed in vacuo, and the residue was dissolved in 55%
aqueous methanol (0.5 mL). Typically, 150-250 MBq of
radiochemically pure 8 was obtained corresponding to 30-50%
decay corrected radiochemical yield.
4-Hydr oxy-4-(4′-n itr oph en yl)-[1-14C]-(1,1,1,3,3-2H5)bu tan -
2-on e (2). Hydroxy ketone 1 (9 MBq) was dissolved in CD3-
OD (10 mL), and 4% NaOD (D2O) (5 drops) was added. The
mixture was stirred for 5 min, and then 2% DCl (D2O) (10
drops) was added. The mixture was poured into D2O (10 mL)
and extracted with CH2Cl2 (3 × 10 mL). The combined CH2-
Cl2 extracts were dried over MgSO4 and concentrated in vacuo.
A 6 MBq sample of 2 was obtained. Analysis by 1H NMR
showed that the deuterium content was at least 95%.
4-F lu or o-4-(4′-n itr op h en yl)-[1-14C]-(1,1,1,3,3-2H5)bu ta n -
2-on e (3). The deuterated hydroxy ketone 2 (6 MBq) was
dissolved in dry CH2Cl2 (3 mL) and cooled to -78 °C under
N2. DAST (20 µL) was added, and the mixture was stirred for
20 min and then heated to rt. The mixture was poured into
D2O (10 mL) and extracted with CH2Cl2 (3 × 5 mL). The
combined CH2Cl2 extracts were dried over MgSO4 and con-
centrated in vacuo. The product was identified by HPLC. A 4
MBq sample of 3 was obtained.
4-H yd r oxy-4-(4′-n it r op h en yl)-(1,1,1,3,3,4-2H 6)b u t a n -2-
on e. 4-Nitro-(R-2H)benzaldehyde (1 g, 6.6 mmol) was dissolved
in acetone-d6 (20 mL) at 0 °C, and NaOD 1% in D2O (0.5 mL,
0.1 mmol) was added. After 10 min, the mixture was neutral-
ized with aqueous HCl and concentrated in vacuo. The brown
residue was dissolved in ether (30 mL) and washed with H2O
(30 mL). Drying over MgSO4, concentration in vacuo, and flash
chromatography on silica Et2O/pentane 2:1 gave 0.8 g (3.7
mmol, 56%) of the title compound. The deuterium content in
the 1-, 3-, and 4-positions was analyzed by 1H NMR and found
to be >98%.
Ack n ow led gm en t. Prof. Bengt Långstro¨m, Uppsala
University PET-center, is gratefully acknowledged for
general radiochemical support and for placing the
excellent facilities of the PET-center at our disposal. We
thank Dr. Nicholas Power for comments on the manu-
script. This project is supported by the Swedish Natural
Science Research Council (NFR).
4-F lu or o-4-(4′-n it r op h e n yl)-(1,1,1,3,3,4-2H 6)b u t a n -2-
on e. 4-Hydroxy-4-(4′-nitrophenyl)-(1,1,1,3,3,4-2H6)butan-2-one
(0.2 g, 0.93 mmol) was dissolved in CH2Cl2 (10 mL) and cooled
to -78 °C. Then DAST (0.15 mL, 1.13 mmol) was added, and
the mixture was stirred for 20 min and then poured into H2O
(30 mL) and extracted with CH2Cl2 (20 mL). After the mixture
J O010773L
Ryberg, Per
