METHOD

Abstract

The present invention relates to new and improved methods of synthesizing radiolabelling agents which can be used to label biomolecules for use as radiopharmaceuticals. It further relates to certain novel radiolabelling agents and their use in such methods. PET imaging methods and methods of diagnosis employing such radiolabelling agents form a further aspect of the invention.

Claims

1-29. (canceled)

30. A compound of formula (I′) or formula (I″), or a salt thereof: ##STR00071## wherein L is a positively charged leaving group selected from —N(C.sub.1-6 alkyl).sub.3.sup.+, 1,4-diazabicyclo[2.2.2]octan-1-ium, and 1-(C.sub.1-3 alkyl)-pyrrolidin-1-ium; R′ is an electron-withdrawing group; and L′ is 1,4-diazabicyclo[2.2.2]octan-1-ium or 1-(C.sub.1-3 alkyl)-pyrrolidin-1-ium.

31. The compound of claim 30, which is a compound of formula (I′) or a salt thereof.

32. The compound of claim 30, which is a compound of formula (I″) or a salt thereof.

33. The compound of claim 30, wherein R′ is —CF.sub.3, —CH.sub.2CF.sub.3, —CH(CF.sub.3).sub.2, —C(CF.sub.3).sub.3, or ##STR00072## where n is an integer from 1 to 5 and each Z is independently —F, —Cl, —NO.sub.2, or —CN.

34. The compound of claim 30, wherein R′ is ##STR00073## where n is an integer from 1 to 5 and each Z is independently —F, —Cl, —NO.sub.2, or —CN.

35. The compound of claim 30, which is a compound of formula (I.sup.n): ##STR00074## where n is an integer from 1 to 5 and each Z is independently —F, —Cl, —NO.sub.2, or —CN.

36. The compound of claim 30, which is a compound of general formula (I.sup.s): ##STR00075## wherein L′ and R′ in said compound of general formula (I.sup.s) are selected such that said compound is one of compounds (8) to (21): TABLE-US-00009 R′ L′ (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21).

37. The compound of claim 30, which is in the form of a trifluoromethanesulphonate salt.

38. The compound of claim 30, which is 5-formyl-N,N,N-trimethylpyridin-2-aminium trifluoromethanesulfonate.

39. The compound of claim 30, which is 1-methyl-1-(5-((2,3,5,6-tetrafluorophenoxy) carbonyl)pyridin-2-yl)pyrrolidin-1-ium trifluoromethanesulfonate.

Description

[0171] The invention will now be illustrated by means of the following non-limiting Examples and the attached Figures in which:

[0172] FIG. 1 shows a schematic for the preparation of [.sup.18F]F-Py-TFP in accordance with the invention as described in non-limiting Example 6.

[0173] FIG. 2 shows a non-limiting schematic of a reaction process for producing [.sup.18F]F-Py-TFP in accordance with the invention, where:

##STR00064##

denotes a solid phase support with anion exchange properties.

[0174] FIG. 3 shows a non-limiting schematic of a reaction process for producing an [.sup.18F]fluorinated compound starting from a precursor having an aldehyde substituent in accordance with the invention.

EXAMPLE 1

Experimental:

[0175] Chemicals and solvents of reagent grade obtained commercially were of a purity of 95% and were used without further purification. Water (ultra-pure, ion-free) was obtained from a Millipore Ultra-pure water system. HPLC solvents were obtained from Merck KGaA (VWR). Synthesis of 6-fluoronicotinic acid 2,3,5,6-tetrafluorophenyl ester (F-Py-TFP) and N,N,N-trimethyl-5-((2,3,5,6-tetrafluorophenoxy)-carbonyl)pyridin-2-aminium trifluoromethanesulfonate was performed as previously reported by Olbeg et al. (J. Med. Chem, 53: 1732-1740).

[0176] Radiochemistry: Radiochemical synthesis was performed manually behind lead shield using aqueous [.sup.18F]fluoride obtained from a cyclotron (GE PETtrace 6) using .sup.18O(p,n).sup.18F nuclear reaction with a 16.5 MeV proton irradiation. Typically experiments were conducted with 30 to 62 MBq of .sup.18F starting radioactivity.

[0177] Analytical HPLC was performed on an Agilent system (1200 series) with UV detection at 214 and 254 nm in series with a γ-detector (Raytest GABI Star 1207 radiometric detector, Straubenhardt, Germany) equipped with C-18 reversed-phase column (ACE analytical 4.6×50, 5μ) using a gradient of 10-95% solvent B in water/0.1% TFA over 10 min with a flow rate of 1.0 mL/min. EZchrome software was used to record and analyze both UV and radiometric data. Radio-TLC was recorded using a Gina Star TLC and analyzed using the Raytest miniGita software (Straubenhardt, Germany). Acetonitrile was used as the mobile phase. Radioactivity was assayed using a calibrated Capintec CRC-15R dose calibrator (Ramsey, N.J., USA)

Experiment 1

[0178] 31.3 MBq of [.sup.18F]fluoride obtained from an aqueous solution was trapped on Chromafix/Chromabond PS-CO.sub.3.sup.− anion exchange column (type shorty, MACHEREY-NAGEL GmbH & Co. KG, Düren, Germany). The column was immediately rinsed with 2 mL of dry acetonitrile and purged with air (6 mL with syringe) after which it was incubated at room temperature with a 0.5 ml mixture containing 22.94 mg of N,N,N-trimethyl-5-((2,3,5,6-tetrafluorophenoxy)-carbonyl)pyridin-2-aminium trifluoromethanesulfonate (1 eq.) precursor, 8 μL DIEPA (1 eq.) in 1:1 acetonitrile/t-BuOH for 2 min and 30 seconds before the solution was pushed completely through the column manually with a syringe filled with air into an empty 3 ml glass vessel (receiving vial) and immediately analyzed by radio-TLC and HPLC. The radioactivity in the receiving vial was 20.5 MBq measured in a dose calibrator 9 min after trapping of [.sup.18F]fluoride (31.3 MBq) on the column. Radio-HPLC showed a major radioactive peak at 254 nm co-eluting with the reference standard, confirming identity, and radio-TLC showed 92.5% radiochemical yield of [.sup.18F]F-Py-TFP.

Experiment 2

[0179] 65.1 MBq of [.sup.18F]fluoride obtained from an aqueous solution was trapped on Chromafix/Chromabond PS-CO.sub.3.sup.− anion exchange column (type shorty, MACHEREY-NAGEL GmbH & Co. KG, Düren, Germany). The column was immediately rinsed with 2 mL of dry acetonitrile and purged with air (6 mL with syringe) after which it was incubated at room temperature with a 0.5 ml mixture containing 30 mg of N,N,N-trimethyl-5-((2,3,5,6-tetrafluorophenoxy)-carbonyl)pyridin-2-aminium trifluoromethanesulfonate (1 eq.) precursor, 14 μL triethylamine (1.5 eq.) in 1:1 acetonitrile/t-BuOH for 2 min and 30 seconds before the solution was pushed completely through the column manually with a syringe filled with air into an empty 3 ml glass vessel (receiving vial) and analyzed by radio-TLC and HPLC. The radioactivity in the receiving vial was 40.5 MBq measured in a dose calibrator 10 min after trapping of [.sup.18F]fluoride (65.1 MBq) on the column. Radio-HPLC showed a major radioactive peak co-eluting with the reference standard (Rt=7.9 min), confirming identity, and radio-TLC showed 95% radiochemical yield of [.sup.18F]F-Py-TFP.

EXAMPLE 2

[0180] Experimental:

[0181] Chemicals and solvents of reagent grade were obtained as detailed in Table 3 and were used without further purification. Water (ultra-pure, ion-free) was obtained from a Millipore Ultra-pure water system. HPLC solvents were obtained from Merck KGaA (VWR).

[0182] Radiochemistry, analytical HPLC, radio-TLC and radioactivity assays were performed as described in the Experimental section of Example 1.

TABLE-US-00003 TABLE 3 Chemical/ d Solvent Supplier Cat. No Grade Lot/Batch MW (g/ml) R S THF Alfa A12686 97% 10181607 NA 36/37/ 26-36 Aesar 38 Dichloromethane Fluka 66749 Puriss 1208726 40 23-24/ 25-36/ 37 1M Acros 388371000 A0338939 NA trimethylamine in THF Trimethylsilyl Aldrich 225649 222.26 1.228 trifluoromethane sulfonate (TMSOTf) 6-chloropyridine- Aldrich 596175 96% MKBF5178 141.56 3-carboxaldehyde

Synthesis of 5-formyl-N,N,N-trimethylpyridin-2-aminium Trifluoromethanesulfonate

[0183] To a solution of 6-chloropyridine-3-carboxaldehyde (700 mg, 4.9 mmol) in THF (5 ml) was added 1 M trimethylamine solution in THF (10.0 mL). The reaction was stirred overnight at room temperature during which a white precipitate formed.

[0184] The precipitate (ammonium chloride salt) was filtered off and washed well with dichloromethane and diethyl ether and dried (Yield: 460 mg, 2.3 mmol). Under an N.sub.2 atmosphere the ammonium salt was suspended in dichloromethane (DCM) (50 ml) cooled on an ice bath and TMSOTf (0.5 mL, 2.5 mmol) was added under vigorous stirring. The reaction was allowed to proceed for 30 min on ice after which it was allowed to reach room temperature. When the solid was completely solubilized in the DCM, the organic phase was removed under vacuum. The solid was taken up in acetonitrile (ACN) and filtered and the filtrate was again taken and treated under vacuum to dryness. The solid was precipitated in diethyl ether and filtered off. The solid was dried under high vacuum for two hours. Yield: 0.656 g, 2.1 mmol (43%) (Faint yellowish solid).

[0185] NMR analysis confirmed the successful synthesis with the following peaks:

[0186] .sup.1H NMR (400 MHz, CD.sub.3CN): δ 1.19 (s, 1H), δ 9.07 (d, J=1.8 Hz, 1H), δ 8.56 (dd, J.sub.1=2.2 Hz, J.sub.2=8.6 Hz, 1H), 8.04 (d, J=8.6 Hz, 1H), 3.58 (s, 9H).

[0187] .sup.13C NMR (101 MHz, CD.sub.3CN): δ 191.40, 151.80, 142.68, 134.65, 117.00, 56.51.

[0188] .sup.19F NMR (376 MHz, CDCl.sub.3): δ-74.03.

Radiolabeling on Solid Phase of 5-formyl-N,N,N-trimethylpyridin-2-aminium Trifluoromethanesulfonate with [.SUP.18.F]fluoride

[0189] 47.2 MBq of [.sup.18F]fluoride obtained from an aqueous solution was trapped on a Chromafix/Chromabond PS-CO.sub.3.sup.− anion exchange column (type shorty, MACHEREY-NAGEL GmbH & Co. KG, Düren, Germany). The column was immediately rinsed with 2 mL of dry acetonitrile and purged with air (6 mL with syringe) after which it was incubated at room temperature with a 0.5 ml mixture containing 20.3 mg of 5-formyl-N,N,N-trimethylpyridin-2-aminium trifluoromethanesulfonate in 1:1 acetonitrile/t-BuOH for 5 minutes before the solution was pushed completely through the column manually with a syringe filled with air into an empty 3 ml glass vessel (receiving vial) and immediately analyzed by HPLC. The radioactivity in the receiving vial was 15.6 MBq measured in a dose calibrator 10 min after trapping of [.sup.18F]fluoride (47.2 MBq) on the column. Radio-HPLC (ACE 3 C.sub.18-50*4.6 mm, 5-50% acetonitrile over 10 min in water/0.05% TFA, 1 ml/min) of eluate showed a major radioactive peak eluting at 3.2 min vs. 1.4 min for precursor. A sample from the receiving vial spiked with reference standard, 6-fluoropyridine-3-carboxaldehyd (t.sub.R=3.16 min), confirmed the identity of the radioactive product using the same above stated HPLC conditions.

Purification of the synthesized 6-[.SUP.18.F]fluoropyridine-3-carboxaldehyde

[0190] The SPE column used was Sep-Pak Oasis™ MCX plus (Waters) (strong cation exchange/with reversed phase properties for trapping unreacted precursor). Conditioning of the SPE column was performed by using 5 mL EtOH then 5 mL MQ water followed by an air purge. The crude reaction product was diluted in water (6 mL) and loaded onto MCX cartridge followed by a 5 mL air purge. The column bound 6-[.sup.18F]Fluoropyridine-3-carboxaldehyde was eluted off with 1 mL ACN.

[0191] 8.72 MBq of pure 6-[.sup.18F]Fluoropyridine-3-carboxaldehyde were obtained from the Oasis MCX cartridge in 1 mL MeCN (19% radiochemical yield, non-decay-corrected, 60 min after start of synthesis). HPLC confirmed removal of the major bulk of the non-reacted precursor from the reaction mixture.

[0192] HPLC and Radio-TLC assays performed in accordance with Example 1 confirmed the purified radiolabelled product, 6-[.sup.18F]Fluoropyridine-3-carboxaldehyde in a radiochemical purity >95%.

EXAMPLE 3

Synthesis of 1-methyl-1-(5-((2,3,5,6-tetrafluorophenoxy)carbonyl)pyridin-2-yl)pyrrolidin-1-ium trifluoromethanesulfonate

[0193] Synthesis of 1-methyl-1-(5-((2,3,5,6-tetrafluorophenoxy)carbonyl)pyridin-2-yl)pyrrolidin-1-ium trifluoromethanesulfonate was performed in line with the synthesis of N,N,N-trimethyl-5-((2,3,5,6-tetrafluorophenoxy)-carbonyl)pyridin-2-aminium trifluoromethanesulfonate as previously reported by Olberg et al. (J. Med. Chem, 53: 1732-1740), but employing N-methyl pyrrolidine in place of trimethylamine:

[0194] To a stirred solution of 2,3,5,6-tetrafluorophenyl 6-chloronicotinate (500 mg, 2.54 mmol) in 5 ml dry THF was added 1 mL of N-methylpyrrolidine. A white precipitate started to form after 10 minutes and reaction was allowed to proceed overnight. The precipitate was collected and washed with cold Et20. The solid residue was suspended in CH.sub.2Cl.sub.2, and TMSOTf (1 mL, 5.29 mmol) was added over 3 min. The mixture was concentrated, and the residue was recrystallized from Et20 to afford 1-methyl-1-(5-((2,3,5,6-tetrafluorophenoxy)carbonyl)pyridin-2-yl)pyrrolidin-1-ium trifluoromethanesulfonate as a white solid (0.70 g, 55%)

[0195] The identity of the synthesised product was confirmed by NMR with the following peaks:

[0196] .sup.1H NMR (400 MHz, Acetonitrile-d.sub.3) δ 9.32 (dd, J=2.3, 0.8 Hz, 1H), δ 8.83 (dd, J=8.7, 2.3 Hz, 1H), δ 8.01 (dd, J=8.7, 0.8 Hz, 1H), δ 7.43 (m, 1H), δ 4.23 (m, 2H), δ 4.01 (m, 2H), δ 3.46 (s, 3H), 2.34 (m, 2H), 2.24 (m, 2H).

[0197] .sup.19F NMR (376 MHz, Acetonitrile-d.sub.3) δ-79.36 (s), δ-140.36 (m), δ-154.41 (m).

Radiolabeling on solid phase of 1-methyl-1-(5-((2,3,5,6-tetrafluorophenoxy)carbonyl)pyridin-2-yl)pyrrolidin-1-ium trifluoromethanesulfonate

[0198] 49.5 MBq of [.sup.18F]fluoride obtained from an aqueous solution was trapped on a Chromafix/Chromabond PS-CO.sub.3.sup.− anion exchange column (type shorty, MACHEREY-NAGEL GmbH & Co. KG, Düren, Germany). The column was immediately rinsed with 2 mL of dry acetonitrile and purged with air (6 mL with syringe) after which it was incubated at room temperature with a 0.5 ml mixture containing 30.24 mg 1-methyl-1-(5-((2,3,5,6-tetrafluorophenoxy)carbonyl)pyridin-2-yl)pyrrolidin-1-ium trifluoromethanesulfonate and 10 μL triethylamine in 1:1 acetonitrile/t-BuOH for 2.5 minutes before the solution was pushed completely through the column manually with a syringe filled with air into an empty 3 ml glass vessel (receiving vial) and immediately analyzed by HPLC. The radioactivity in the receiving vial was 23.0 MBq measured in a dose calibrator 14 min after trapping of [.sup.18F]fluoride (49.5 MBq) on the column. Radio-HPLC (ACE 3 C18-50*4.6 mm, 10-90% acetonitrile over 10 min in water/0.05% TFA, 1 ml/min) of the eluate showed a major radioactive peak co-eluting with F-Py-TFP reference standard at 7.890 min.

EXAMPLE 4

[0199] Solid-phase labeling experiments were carried out using Chromafix (Chromabond PS-HCO.sub.3) as the stationary phase. Details are shown in Table 4, where:

[0200] Column A is the experiment number

[0201] Column B is the precursor amount in mg

[0202] Column C identifies the solvent and its overall volume in mL; thus, for example, “1:1

[0203] t-BuOH/MeCN/0.5” refers to a 1:1 mixture of t-BuOH and MeCN with an overall volume of 0.5 mL

[0204] Column D identifies the base

[0205] Column E identifies the amount of Chromafix PS-HCO.sub.3 resin employed in mg

[0206] Column F identifies the initial radioactivity trapped on the column MBq

[0207] Column G identifies the experiment start time (hh:mm)

[0208] Column H identifies the radioactivity in MBq in the vial used to receive the eluted radiolabelled product

[0209] Column I identifies the experiment end time (hh:mm)

[0210] Column J identifies the reaction yield (%) identified by radio-TLC

[0211] Column K identifies the elution efficiency (%)

[0212] Column L identifies the total yield (not decay-corrected) in %

TABLE-US-00004 TABLE 4 A B C D E F** G H I J** K*** L**** 1 21 MeCN/1 NA 45 62.8 14:06 22.4 14:25 63.3 35.7 22.6 2 NA MeCN/1 + 1 NA NA NA NA 23.1 NA 79.7 NA NA 3 41 MeCN/0.5 NA 45 64.0 15:00 25.7 15:15 88.6 40.1 35.5 4 NA MeCN/0.5 NA 45 20.7 15:19 34.4 15:20 94.8 NA NA 5 45.7 MeCN/1 NA 45 35.2 13:24 14.3 13:40 75.7 40.1 30.4 6 NA NA NA 45 NA NA NA NA 81.0 NA NA 7 24.8 1:1 NA 45 37.5 14:27 32.9 14:26 0 91.4 0 MeOH/MeCN/ 0.5 8 21 1:1 NA 45 36.0 15.31 2.19 15:38 95.3 60.8 57.9 t-BuOH/MeCN/ 0.5 9 NA NA NA NA NA NA NA NA 98.4 60.8 NA 10 23 1:1 NH.sub.4OTf 45 47.9 11:18 12.5 11:27 17.0 26.1 4.4 t-BuOH/MeCN/ 0.5 11 22 8:2 NA 45 25.9 11:43 11.4 11:51 89.6 44.0 39.4 t-BuOH/MeCN/ 0.5 12 40 1:1 NA 25 41.7 13:55 20.3 14:05 87.7 48.7 42.7 t-BuOH/MeCN/1 13 20 1:1 NA 45 29.5 14:15 8.7 14:22 90.2 29.5 26.6 t-BuOH/MeCN/ 0.5 14 20 1:1 NA 45 40.6 15:38 18.8 15:47 81.8 46.3 37.9 t-BuOH/MeCN/ 0.5 15 40 1:1 NA  45# 27.5 11:50 9.6 12:00 76.8 34.9 26.8 t-BuOH/MeCN/ 0.5 16 40 1:1 NA 10 27.2 12:26 12.1 12:33 NA 44.5 NA t-BuOH/MeCN/ 0.5 17 22 1:1 NA ## 33.6 13:27 0.3 13:33 NA 0.9 NA t-BuOH/MeCN/ 0.5 18 23 1:1 DIPEA 45 30.9 14:19 20.5 14:26 92.5 66.3 61.3 t-BuOH/MeCN/ 8 μL 0.5 19 23 1:1 DIPEA 8 μL + 45 22.5 15:12 15.2 15:19 78.7 67.6 53.2 t-BuOH/MeCN/ TBAOTf 0.5 20 15 1:1 NA 45 NA NA NA NA NA NA NA t-BuOH/MeCN/ 0.5 21 20 1:1 DIPEA 5 μL 45 23.2 14:17 8.7 14:24 NA 37.5 NA t-BuOH/MeCN/ 0.5 22 24 1:1 DIPEA 45 16.2 14:53 10.0 14:59 NA 61.7 NA t-BuOH/MeCN/ 10 μL 0.5 23 23 1:1 DIPEA 45 43.4 15:19 29.3 15:26 70.7 67.5 47.7 t-BuOH/MeCN/ 12 μL 0.5 24 20 1:1 TEA 45 44.6 15:32 24.6 15:40 NA 55.2 NA t-BuOH/MeCN/ 6 μL 0.5 25 30 1:1 TEA 45 63.2 14:44 40.5 14:50 95.1 64.1 61.0 t-BuOH/MeCN/ 14 μL 0.5 26 22 1:1 DIPEA 45 28.7 11:57 15.7 12:05 66.0 54.7 37.7 t-BuOH/MeCN/ 10 μL 0.5 27 22 1:1 TEA 45 24.3 12:17 13.7 12:22 42.3 56.4 23.9 t-BuOH/MeCN/ 10 μL 0.5 28 45 1:1 TEA 45 39.6 13:36 20.7 13:44 98.24***** 52.3 NA t-BuOH/MeCN 20 μL 0.5 29 23 1:1 TEA 45 46.2 15:03 27.4 15:13 36.7 59.3 21.7 t-BuOH/MeCN/1 20 μL NA = not applicable *After rinsing column with MeCN **Mobile phase 100% MeCN (some hydrolysis of ester may occur during drying of TLC strip (silica), and actual yield may be under estimated depending on hold-up time of sample on strip) ***Elution efficiency is not corrected for decay and therefore slightly underestimated depending on time between measurements ****RCY by radio-TLC multiplied by elution efficiency *****Purity after C18 Sep-Pak purification. 16.2 MBq eluted in 1 ml diethyl ether (13:55) from column showing 17. MBq at 13:51, 0.81 MBq remaining on column at 13:56 #conditioned with KOTf 0.2M ## Waters QMA resin 10 mg

[0213] Comments to Entries in Table 4: [0214] 1. Eluted over 10 minutes (500+200+300). 2 mL MeCN followed by 110 sec He 1000 mL/min [0215] 2. Column from 1 re-eluted with additional 1 mL neat MeCN to reaction mixture of entry 1 and heated at 40° C. for 10 min [0216] 3. Column treated with He-gas for 120 sec after wash with MeCN. 10 min incubation of precursor mixture on column [0217] 4. Same column from 3 re-treated with 0.5 of precursor mix (41 mg/mL) and 10 min incubation, eluted to mixture of 3—elution mix heated to 40° C. for 10 min. Some radioactivity lost to sampling. [0218] 5. Elution done in steps over 5 min—pulling Rx back and forth over column. [0219] 6. Same as 5 heated to 50° C. for 10 min [0220] 7. 2 min soak—no Rx. [0221] 8. 2 min and 30 sec soak. (2 ml MeCN rinse before Rx)—remaining 12.7 MBq on column at 15:37 [0222] 9. Same 9 reaction mixture heated to 40° C. for 5 min [0223] 10. 2 min and 30 sec soak. 60 μL of 1M NH.sub.4OTf added to elution mixture (Triflate salt acidic—impurities can be adjusted with base) [0224] 11. 2 min and 30 sec soak [0225] 12. Elution mix pushed in steps over 5 min. Pressure was also applied to column when eluting [0226] 13. Elution mix pushed in steps over 5 min [0227] 14. 250 μL of precursor eluent pushed through column and column heated in Scansys reactor at 60° C. for 5 min before eluting with last 250 μL of precursor eluent [0228] 15. i) Cartridge washed with 10 mL MQ water [0229] ii) Conditioning with KOTf.sub.(aq) (0.2 M) 10 mL [0230] ii) Wash with water—10 mL [0231] Rx with precursor mixture in two steps—where elution mix is reintroduced over column a 2.sup.nd time (only final result reported). 1 mL of 0.9% NaCl releases remaining activity on column [0232] 16. 0.5 MBq bleed through column (12:32). Dropwise elution over 2 min. No effect of re-elution with reaction mixture [0233] 17. Rx—with silica based anion-exchange resin. 2 min and 30 sec soak. Practically no activity eluted off column [0234] 18. Non-nucleophilic base added to elution mixture. 2 min and 30 sec soak. No apparent precipitation after 30 min [0235] 19. TBA-OTf in t-BuOH/MeCN 1:1 20 μL added to precursor mixture. 2 min and 30 sec soak [0236] 20. Added 10 μL of 0.9% NaCl to elution mixture. Only 10% activity off column [0237] 21. Column rinse with only 1 mL acetonitrile. 2 min and 30 sec soak [0238] 22. 2 min and 30 sec soak. Column rinse with only 2 mL acetonitrile [0239] 23. 2 min and 30 sec soak. Column rinse with only 2 mL acetonitrile [0240] 24. New batch of Chromabond PS—HCO.sub.3 columns. 2 min and 30 sec soak. Column rinse with only 2 mL acetonitrile [0241] 25. Chromabond not conditioned with water before use, incubated with MeCN for 30 min before use [0242] 26. No conditioning of column, observed no bleed through of fluoride. Soak with MeCN (5 min) after trapping fluoride. Column rinse with only 2 mL acetonitrile [0243] 27. MeCN conditioning of column (5 min), no bleed through of fluoride. Column rinse with only 2 mL acetonitrile (as normally done). 2 min and 30 sec soak [0244] 28. 2 min and 30 sec soak. Crude loaded onto C18 Sep-Pak after diluting with 5 ml 2% acetic acid solution, rinsed with water (5 mL) and eluted off with diethyl ether (1 mL) [0245] 29. Column conditioned with water and then 5 min soak with MeCN before use

EXAMPLE 5

[0246] Solid-phase labeling experiments were carried out using various different resins as the stationary phase. Chromafix (Chromabond PS-HCO.sub.3), as employed in Example 4, was used as a control (entry 3 in the table). Details are shown in Table 5, where Columns A-D and F-L denote the same meanings as in Example 4. Column E identifies the type and amount of anion exchange resin employed in mg, with bicarbonate as the counterion. Table 5:

TABLE-US-00005 A B C D E F* G H I J** K*** L**** 1 30 1:1 TEA Bakerbond 22.7 12:22 5.6 12:32 NA# 24.7 NA t-BuOH/ (14 μL) XWP 500 MeCN/0.5 PolyQuat- 35/41 mg 2 30 1:1 TEA Waters 27.4 12:46 15 12:54 70.0 56.6 39.6 t-BuOH/ (14 μL) Oasis MAX MeCN/0.5 resin/43 mg 3 30.4 1:1 t- TEA Chromabond- 28.3 13:15 17.7 15:23 95.8 62.5 59.9 BuOH/MeCN/ (14 μL) PS HCO.sub.3- 0.5 45 mg 4 22 1:1 t- NA Waters 32.3 13:24 0.3 13:33 NA 0.93 NA BuOH/MeCN/ QMA resin/ 0.5 10 mg #= poor elution. *After rinsing column with MeCN **Mobile phase 100% MeCN (some hydrolysis of ester may occur during drying of TLC strip (silica), and actual yield may be under estimated depending on hold-up time of sample on strip) ***Elution efficiency is not corrected for decay and therefore slightly underestimated depending on time between measurements ****RCY by radio-TLC multiplied by elution efficiency

[0247] Comments to Entries in Table 5: [0248] 30. 2 min and 30 sec soak. Column rinse with only 2 mL acetonitrile. HPLC confirms product in high radiochemical purity. (Polymer based) [0249] 31. 2 min and 30 sec soak. Column rinse with only 2 mL acetonitrile. HPLC and TLC confirms product in high radiochemical purity. (Polymer based) [0250] 32.2 min and 30 sec soak. Column rinse with only 2 mL acetonitrile (as normally done). HPLC and TLC confirms product in high radiochemical purity. (Polymer based) [0251] 33. Practically no elution using Waters QMA resin (silica based)

EXAMPLE 6

[0252] FIG. 1 shows a schematic example of the synthesis of [.sup.18F]F-Py-TFP using the process of the invention. A Chromafix PS-HCO.sub.3.sup.− cartridge (a strong PS/DVB anion exchanger in HCO.sub.3.sup.− form) is loaded with 1 to 5 mL of aqueous [.sup.18F]F.sup.−. The cartridge is dried by rinsing with 2 mL dry acetonitrile and then 5-10 ml of air.

[0253] 20 mg of precursor (N,N,N-trimethyl-5[(2,3,5,6-tetrafluorophenoxy)carbonyl]pyridin-2-aminium trifluoromethanesulfonate) in 8 μl N,N-diisopropylethylamine are eluted through the column for 2 to 3 minutes at room temperature. Following the elution of the precursor the cartridge is rinsed with 250 μl dry acetonitrile and 250 μl dry t-BuOH. [.sup.18F]F-Py-TFP is recovered in good yield.

EXAMPLE 7

Radiolabelling of 5-(((1,1,1,3,3,3-hexafluoropropan-2-yl)oxy)carbonyl)-N,N,N-trimethylpyridin-2-aminium Trifluoromethanesulfonate

[0254] ##STR00065##

5-(((1,1,1,3,3,3-hexafluoropropan-2-yl)oxy)carbonyl)-N,N,N-trimethylpyridin-2-aminium Trifluoromethanesulfonate

[0255] Experimental:

Preparation of 1,1,1,3,3,3-hexafluoropropan-2-yl 6-chloronicotinate

[0256] To a stirred solution of 6-chloronicotinic acid (500 mg, 3.17 mmol) and N,N′-dicyclohexylcarbodiimide (DCC) (648 mg, 3.16 mmol) in tetrahydrofuran (THF) (15 mL) was added 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP) (401 μL, 3.81 mmol) and a catalytic amount of 4-dimethylaminopyridine (DMAP). The mixture was stirred for 48 h at room temperature. The organic phase was removed in vacuo after which the solid residue was purified by silica gel flash chromatography (hexanes:ethyl acetate 1:1) 1,1,1,3,3,3-hexafluoropropan-2-yl 6-chloronicotinate was obtained as a colourless solid (780 mg, 2.54 mmol).

Preparation of 5-(((1,1,1,3,3,3-hexafluoropropan-2-yl)oxy)carbonyl)-N,N,N-trimethylpyridin-2-aminium Trifluoromethanesulfonate

[0257] 1,1,1,3,3,3-hexafluoropropan-2-yl 6-chloronicotinate (780 mg, 2.54 mmol) was dissolved in 5 ml dry THF after which was added 1 M trimethylamine solution in THF (5.0 mL). A white precipitate was found 10 minutes after the reaction started, which was allowed to proceed overnight. The precipitate was collected and washed with cold Et20. The solid residue was suspended in CH.sub.2Cl.sub.2, and TMSOTf (1 mL, 5.29 mmol) was added over 3 minutes. The mixture was concentrated, and the residue was recrystallized from Et20 to afford 5-(((1,1,1,3,3,3-hexafluoropropan-2-yl)oxy)carbonyl)-N,N,N-trimethylpyridin-2-aminium trifluoromethanesulfonate as a white solid (0.55 g, 45% yield).

[0258] Formation of 5-(((1,1,1,3,3,3-hexafluoropropan-2-yl)oxy)carbonyl)-N,N,N-trimethylpyridin-2-aminium trifluoromethanesulfonate was confirmed by NMR:

[0259] .sup.1H NMR (400 MHz, Acetonitrile-d.sub.3) δ 9.22 (d, J=2.3 Hz, 1H), δ 8.74 (dd, J=8.8, 2.3 Hz, 1H), δ 8.03 (d, J=8.7 Hz, 1H), δ 6.46 (m, 1H), δ 3.58 (s, 9H).

[0260] .sup.19F NMR (376 MHz, Acetonitrile-d.sub.3) δ-73.72, δ-79.36.

Radiolabeling on solid phase of 5-(((1,1,1,3,3,3-hexafluoropropan-2-yl)oxy)carbonyl)-N,N,N-trimethylpyridin-2-aminium trifluoromethanesulfonate

[0261] 84.8 MBq of [.sup.18F]fluoride obtained from an aqueous solution was trapped on a Chromafix/Chromabond PS-CO3-anion exchange column (type shorty, MACHEREY-NAGEL GmbH & Co. KG, Düren, Germany). The column was immediately rinsed with 2 mL of dry acetonitrile and purged with air (6 mL with syringe) after which it was incubated at room temperature with a 0.5 ml mixture containing 31.2 mg of 5-(((1,1,1,3,3,3-hexafluoropropan-2-yl)oxy)carbonyl)-N,N,N-trimethylpyridin-2-aminium trifluoromethanesulfonate in 1:1 acetonitrile/t-BuOH for 2.5 minutes before the solution was pushed completely through the column manually with a syringe filled with air into an empty 3 ml glass vessel (receiving vial) and immediately analyzed by HPLC. The radioactivity in the receiving vial was 48.4 MBq measured in a dose calibrator 10 min after trapping of [.sup.18F]fluoride (84.8 MBq) on the column. Radio-HPLC (ACE 3 C18-50*4.6 mm, 10-90% acetonitrile over 10 min in water/0.05% TFA, 1 ml/min) of eluate showed a major radioactive peak eluting at 7.893 min expected to be 1,1,1,3,3,3-hexafluoropropan-2-yl 6-[.sup.18F]fluoronicotinate (.sup.18F-Py-HFIP).

##STR00066##

[0262] .sup.18F-Py-HFIP (1,1,1,3,3,3-hexafluoropropan-2-yl-6-[.sup.18F]fluoronicotinate)

EXAMPLE 8

[0263] AG® MP-1M Anion Exchange Resins of mesh size 200-400 and 50-100 (each 42 mg) were weighed out in two empty Chromafix columns (shorty MACHEREY-NAGEL GmbH & Co. KG, Dren, Germany) and converted from chloride form to the HCO.sub.3.sup.− form by passing a 10 mL 1M KHCO.sub.3 solution over the resins, followed by 10 mL Milli-Q water and then dried with air. 5 to 10 MBq of [.sup.18F]fluoride obtained from an aqueous solution was trapped on the AG resins.

[0264] The columns were immediately rinsed with 2 mL of dry acetonitrile and purged with air (6 mL with syringe) after which they were incubated at room temperature with a 0.5 ml mixture containing 22.94 mg of N,N,N-trimethyl-5-((2,3,5,6-tetrafluorophenoxy)-carbonyl)pyridin-2-aminium trifluoromethanesulfonate (1 eq.) precursor, 10 μL TEA (triethylamine) (1 eq.) in 1:1 acetonitrile/t-BuOH for 2 min and 30 seconds before the solution was pushed completely through the column manually with a syringe filled with air into an empty 3 ml glass vessel (receiving vial) and immediately analyzed by radio-TLC and HPLC. Radio-HPLC showed a major radioactive peak at 254 nm co-eluting with the reference standard, confirming identity, and radio-TLC showed 92.5% radiochemical yield of [.sup.18F]F-Py-TFP. The radiochemical yields and purities can be found in Table 6.

TABLE-US-00006 TABLE 6 BioRad polymer resin solid-phase labeling results of .sup.18F-Py-TFP Entry A B C D E F G H I J K L 1 BioRad 30 C1 TEA 42.3 8.90 16:21 5.76 16:31 76.8 65 49.8 AG- −10 μL MP-1M (200-400 mesh) 2 BioRad 30 C2 TEA 43.6 5.04 16:54 1.70 17:02 28.9 34 9.9 AG- −10 μL MP-1M (50-100 mesh) Key to Table 6: A: Resin B: Precursor amount (mg) C: Solvent system (ml) C1: 1:1 t-BuOH/MeCN/0.5 C2: 1:1 t-BuOH/MeCN/0.5 D: Base E: Resin amount (mg) F: Start activity trapped on column (MBq)* G: Time start (hh:mm) H: Activity in receiving vial (MBq) I: Time end (hh:mm) J: RCY % by radio-TLC** K: Elution efficiency (%)*** L: Total yield no decay corrected (%)**** *After rinsing column with MeCN **Mobile phase 100% MeCN (some hydrolysis of ester may occur during drying of TLC strip (silica), and actual yield may be under estimated depending on hold-up time of sample on strip) ***Elution efficiency is not corrected for decay and therefore slightly underestimated depending on time between measurements ****RCY by radio-TLC multiplied by elution efficiency

EXAMPLE 9

[0265] 40.2 MBq of [.sup.18F]fluoride obtained from an aqueous solution was trapped on Chromafix/Chromabond PS-CO.sub.3.sup.− anion exchange column (type shorty, MACHEREY-NAGEL GmbH & Co. KG, Düren, Germany). The column was immediately rinsed with 2 mL of dry absolute ethanol and purged with air (2 mL with syringe) after which it was incubated at room temperature with a 0.5 ml mixture containing 31.93 mg of N,N,N-trimethyl-5-((2,3,5,6-tetrafluorophenoxy)-carbonyl)pyridin-2-aminium trifluoromethanesulfonate (1 eq.) precursor, 10 μL DIEPA (1 eq.) in 1:1 acetonitrile/t-BuOH for 2 min and 30 seconds before the solution was pushed completely through the column manually with a syringe filled with air into an empty 3 ml glass vessel (receiving vial) and immediately analyzed by radio-TLC and HPLC. The radioactivity in the receiving vial was 32.4 MBq measured in a dose calibrator 8 min after trapping of [.sup.18F]fluoride (39.6 MBq) on the column. Radio-HPLC showed a major radioactive peak at 254 nm co-eluting with the reference standard, confirming identity, and radio-TLC showed 28% radiochemical yield of [.sup.18F]F-Py-TFP.

TABLE-US-00007 TABLE 7 Using 1 mL EtOH (abs.) replacing MeCN for removing water from ion-exchange cartridge after trapping .sup.18F.sup.− Entry A B C D E F G H I J K L 1 Chromafix 31 C1 DIPEA 45 39.6 13:21 32.4 13:29 35 81.2 28 PS-CO3- −10 μL anion exchange column (type shorty) Key to Table 7: A: Resin B: Precursor amount (mg) C: Solvent system (ml) C1: 1:1 t-BuOH/MeCN/0.5 D: Base E: Resin amount (mg) F: Start activity trapped on column (MBq)* G: Time start (hh:mm) H: Activity in receiving vial (MBq) I: Time end (hh:mm) J: RCY % by radio-TLC** K: Elution efficiency (%)*** L: Total yield no decay corrected (%)**** *After rinsing column with EtOH **Mobile phase 100% MeCN (some hydrolysis of ester may occur during drying of TLC strip (silica), and actual yield may be under estimated depending on hold-up time of sample on strip) ***Elution efficiency is not corrected for decay and therefore slightly underestimated depending on time between measurements ****RCY by radio-TLC multiplied by elution efficiency

EXAMPLE 10

[0266] 97.4 MBq of [.sup.18F]fluoride obtained from an aqueous solution was trapped on Chromafix/Chromabond PS-CO.sub.3.sup.− anion exchange column (type shorty, MACHEREY-NAGEL GmbH & Co. KG, Düren, Germany). The column was immediately rinsed with 2 mL of dry acetonitrile and purged with air (2 mL with syringe) after which it was incubated with a 0.5 ml mixture containing 31.93 mg of N,N,N-trimethyl-5-((2,3,5,6-tetrafluorophenoxy)-carbonyl)pyridin-2-aminium trifluoromethanesulfonate (1 eq.) precursor, 10 μL TEA (1 eq.) in 1:1 acetonitrile/t-BuOH for 2 min and 30 seconds simultaneously using a heat gun blowing hot air over the cartridge (60-70° C. at surface of cartridge) before the solution was pushed completely through the column manually with an air filled syringe into an empty 3 ml glass vessel (receiving vial) and immediately analyzed by radio-TLC and HPLC. The radioactivity in the receiving vial was 72.4 MBq measured in a dose calibrator 11 min after trapping of [.sup.18F]fluoride (93.9 MBq) on the column. Radio-HPLC showed a major radioactive peak at 254 nm co-eluting with the reference standard, confirming identity, and radio-TLC showed 92% radiochemical yield of [.sup.18F]F-Py-TFP.

TABLE-US-00008 TABLE 8 With heating using heatgun a 5 cm distance over column for 3 min (60-70 C.°) Entry A B C D E F G H I J K L 1 Chromafix 30 C1 DIPEA 45 93.9 00:00 74.2 00:11 92 79 72.7 PS-CO3- −10 μL anion exchange column (type shorty) Key to Table 8: A: Resin B: Precursor amount (mg) C: Solvent system (ml) C1: 1:1 t-BuOH/MeCN / 0.5 D: Base E: Resin amount (mg) F: Start activity trapped on column (MBq)** G: Time start (hh:mm) H: Activity in receiving vial (MBq) I: Time end (hh:mm) J: RCY % by radio-TLC** K: Elution efficiency (%)*** L: Total yield no decay corrected (%)****

EXAMPLE 11

Synthesis and radiolabelling of 1-methyl-1-(5-((2,3,5,6-tetrafluorophenoxy)carbonyl)pyridin-2-yl)pyrrolidin-1-ium trifluoromethanesulfonate

[0267] ##STR00067##

Synthesis

[0268] To a stirred solution of 2,3,5,6-tetrafluorophenyl 6-chloronicotinate (500 mg, 2.54 mmol) in 5 ml dry THF was added 1 mL of N-methylpyrrolidine. A white precipitate started to form after 10 min and reaction was allowed to proceed overnight. The precipitate was collected and washed with cold Et20. The solid residue was suspended in CH.sub.2Cl.sub.2, and TMSOTf (1 mL, 5.29 mmol) was added over 3 min. The mixture was concentrated, and the residue was recrystallized from Et20 to afford 1-methyl-1-(5-((2,3,5,6-tetrafluorophenoxy)carbonyl)pyridin-2-yl)pyrrolidin-1-ium trifluoromethanesulfonate as a white solid (0.70 g, 55%)

[0269] .sup.1H NMR (400 MHz, Acetonitrile-d.sub.3) δ 9.32 (dd, J=2.3, 0.8 Hz, 1H), δ 8.83 (dd, J=8.7, 2.3 Hz, 1H), δ 8.01 (dd, J=8.7, 0.8 Hz, 1H), δ 7.43 (m, 1H), δ 4.23 (m, 2H), δ 4.01 (m, 2H), δ 3.46 (s, 3H), 2.34 (m, 2H), 2.24 (m, 2H).

[0270] .sup.19F NMR (376 MHz, Acetonitrile-d.sub.3) δ-79.36 (s), 6-140.36 (m), 6-154.41 (m).

[0271] Radiolabelling:

[0272] 49.5 MBq of [.sup.18F]fluoride obtained from an aqueous solution was trapped on a Chromafix/Chromabond PS-CO3-anion exchange column (type shorty, MACHEREY-NAGEL GmbH & Co. KG, Düren, Germany). The column was immediately rinsed with 2 mL of dry acetonitrile and purged with air (6 mL with syringe) after which it was incubated at room temperature with a 0.5 ml mixture containing 30.24 mg 1-methyl-1-(5-((2,3,5,6-tetrafluorophenoxy)carbonyl)pyridin-2-yl)pyrrolidin-1-ium trifluoromethanesulfonate and 10 μL triethylamine in 1:1 acetonitrile/t-BuOH for 2.5 minutes before the solution was pushed completely through the column manually with a syringe filled with air into an empty 3 ml glass vessel (receiving vial) and immediately analyzed by HPLC. The radioactivity in the receiving vial was 23.0 MBq measured in a dose calibrator 14 min after trapping of [.sup.18F]fluoride (49.5 MBq) on the column. Radio-HPLC (ACE 3 C18-50*4.6 mm, 10-90% acetonitrile over 10 min in water/0.05% TFA, 1 ml/min) of the eluate showed a major radioactive peak co-eluting with F-Py-TFP reference standard at 7.890 min.

EXAMPLE 12

[0273] Radiosynthesis of [.sup.18F]DCFPyL was carried out according to the protocol described below and illustrated in Scheme 1.

[0274] PSMA precursor (Glu-CO-Lys) was obtained from ABX GmBH (Germany).

[0275] [.sup.18F]F-Py-TFP synthesized “on-cartridge” was purified by diluting the downstream eluate (500 μL) with 5 mL 10% AcOH and trapped on a tC18 Sep-Pak Plus cartridge. The cartridge was washed with water (10 mL), and dried with helium-flow. [.sup.18F]F-Py-TFP was eluted off the C.sub.18 cartridge with diethyl ether (2 mL) simultaneously passing the eluate through an Na.sub.2SO.sub.4 drying cartridge (Sep-Pak plus long, Waters). The diethyl ether was removed using a helium sweep gas. The purified [.sup.18F]F-Py-TFP was reconstituted in 500 μL acetonitrile.

[0276] To two separate glass vials each containing 1 mg PSMA (Glu-CO-Lys) precursor in 222 uL DMSO was added 2 μL TEA followed by 100 μL of radiochemical pure [.sup.18F]F-Py-TFP (90 MBq) in MeCN. Reaction was allowed to proceed for 1 h (vial 1) at room temperature and 10 min at 65° C. (vial 2). Radio-HPLC indicated 89% (vial 1) and 85% (vial 2) conversion to [.sup.18F]DCFPyL. Radiolabeled products co-eluted with an authentic DCFPyL reference sample (R.sub.T=3.257 min). Radio-HPLC (ACE 3 C18-50*4.6 mm, 10% ACN in H.sub.2O/0.05% TFA isocratic, 5 min, then to 95% ACN over 9 min, 1 ml/min).

##STR00068##

EXAMPLE 13

[0277] [.sup.18F]MEL050 was Synthesised from N,N-diethyleneethylenediamine and .sup.18F-Py-TFP According to the Protocol Described Below and Illustrated in Scheme 2:

##STR00069##

[0278] MEL050 Synthesis (Reference Standard):

[0279] 2-(diethylamino)-ethyl)-6-fluoronicotinamide (MEL050) was synthesized and characterized according to the method described in Greguric, I, et al. Journal of Medicinal Chemistry 2009 52 (17), 5299-5302, accessible at DOI: 10.1021/jm9008423, the entire contents of which are incorporated herein by reference.

[0280] [.sup.18F]Mel050 Synthesis:

[0281] 21.21 MBq of aqeuous fluoride-18 was trapped on Chromafix PS-HCO.sub.3 cartridge (type shorty, MACHEREY-NAGEL GmbH & Co. KG, Düren, Germany). The column was immediately rinsed with 2 mL of dry acetonitrile and purged with air (6 mL with syringe) after which it was incubated at room temperature with a 0.5 ml mixture containing 27.6 mg 1-methyl-1-(5-((2,3,5,6-tetrafluorophenoxy)carbonyl)pyridin-2-yl)pyrrolidin-1-ium trifluoromethanesulfonate, 10 μL triethylamine in 1:1 acetonitrile/t-BuOH (500 μL) for 2.5 minutes before the solution was pushed manually and completely through the column with a syringe filled with air into an empty 3 ml glass vessel (receiving vial). The radioactivity in the receiving vial was 16.8 MBq measured in a dose calibrator 8 min after trapping of [.sup.18F]fluoride (22.21 MBq) on the column.

[0282] 10 μL N,N-diethyleneethylenediamine was added directly to the receiving vial containing the [.sup.18F]F-Py-TFP eluate, reacted for 5 min at room temperature and analyzed by radio-TLC and radio-HPLC to verify identity (by co-elution with reference standard) and radiochemical yield. Radio-HPLC and TLC indicated full conversion from [.sup.18F]F-Py-TFP to [.sup.18F]MEL050. Free fluoride-18 was removed by trapping the radioactive product after diluting the reaction mixture with water (1:20), loading it onto an Oasis MCX plus cartridge (Waters) followed by a water rinse (5 ml). 7.55 MBq of product was retained on the Oasis MCX plus (Waters) 27 minutes after start of synthesis. A mixture of 5% acetic acid with trimethylamine in water/ethanol (1:1) eluted off radiochemical pure [.sup.18F]MEL050 (>99% radiochemical purity) in which co-eluted with an authentic reference sample of MEL50 (R.sub.T=3.53 min). Radio-HPLC (ACE 3 C18-50*4.6 mm, 3-40% acetonitrile over 10 min in water/0.05% TFA, 1 ml/min).

EXAMPLE 14

[0283] [.sup.18F]F-Py-TFP is prepared as described herein and then reacted with biomolecules of general formula (C) in which n is 1, 2, 3, 4, 5, 6, 7, 8 or 9. The reaction is carried out in the presence of TEA and DMSO at room temperature for 1 hour, or at 65° C. for 10 minutes. In an alternative approach the reaction is carried out in the presence of tetraethylammonium bicarbonate and ethanol at 40° C. for 3 minutes.

[0284] [18F]DCFPyL (where n=4) and analogues with n=1, 2, 3, 5, 6, 7, 8 and 9 are obtained.

##STR00070##