WO1989007106A1 - Method of making radioiodinated pyrimidine - Google Patents

Method of making radioiodinated pyrimidine Download PDF

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Publication number
WO1989007106A1
WO1989007106A1 PCT/US1989/000358 US8900358W WO8907106A1 WO 1989007106 A1 WO1989007106 A1 WO 1989007106A1 US 8900358 W US8900358 W US 8900358W WO 8907106 A1 WO8907106 A1 WO 8907106A1
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water
nucleotide
insoluble
oxidizing agent
nucleoside
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French (fr)
Inventor
Amin I. Kassis
Janina BARANOWSKA-KORTYLEWICS
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Harvard University
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Harvard University
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Priority to EP89903657A priority Critical patent/EP0403544B1/en
Priority to JP50328589A priority patent/JPH0637509B2/en
Priority to DE68922489T priority patent/DE68922489T2/en
Publication of WO1989007106A1 publication Critical patent/WO1989007106A1/en
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07H—SUGARS; DERIVATIVES THEREOF; NUCLEOSIDES; NUCLEOTIDES; NUCLEIC ACIDS
    • C07H19/00—Compounds containing a hetero ring sharing one ring hetero atom with a saccharide radical; Nucleosides; Mononucleotides; Anhydro-derivatives thereof
    • C07H19/02—Compounds containing a hetero ring sharing one ring hetero atom with a saccharide radical; Nucleosides; Mononucleotides; Anhydro-derivatives thereof sharing nitrogen
    • C07H19/04—Heterocyclic radicals containing only nitrogen atoms as ring hetero atom
    • C07H19/06—Pyrimidine radicals

Definitions

  • Radioiodinated pyrimidine nucleosides such as 5-iodo-2'-deoxyuridine have, been used for many years to label the DNA of proliferating cells in studies of tumor transplantation and of DNA structure among other uses.
  • Radioiodination methods for making such compounds have included electrophilic substitution of hydrogen in the pyrimidine ring by reacting water-soluble pyrimidine nucleosides in aqueous solution with sodium iodide and nitric acid as described by Keough et al., J. Labelled Compd. Radiopharm., Vol. 14, pp. 83-90 (1978) and with sodium iodide and chloramine-T as described by Bakker et al., Int. J. Appl. Radiat.
  • the process of the present invention can be applied to any water-insoluble halomercuri-pyrimidine nucleoside such as 5-chloromercuri cytidine, 5-chloromercuri-2'-deoxycytidine, 5-chloromercuri uridine, 5-chloromercuri-2'-deoxyuridine, or water-insoluble halomercuri-pyrimidine nucleotide" such as 5-chloromercuri-cytidine-5'-mono-, di, or tri-phosphate, 5-chloromercuri-2'-deoxycytidine-5'-mono-, di-, or tri-phosphate, 5-chloromercuri-uridine-5'-mono-, di-, or tri-phosphate, or 5-chloromercuri-2'-deoxyuridine-5'-mono-, di-, or tri-phosphate; the corresponding 5-fluoromercuri compounds, and the like may also be used.
  • the water-insoluble nucleosides and nucleotides can
  • the radioactive iodide ion may be employed in the form of any water-soluble salt, e.g. an alkali metal salt such as the sodium salt of 123 I, 125 I, 131 I, preferably in carrier-free form.
  • an alkali metal salt such as the sodium salt of 123 I, 125 I, 131 I, preferably in carrier-free form.
  • the oxidizing agent used may be either water-soluble as in the case of Chloramine-T or nitric acid; or it may be water-insoluble as in the case of iodogen (1,3,4,6-tetrachloro-3 ⁇ , 6 ⁇ -diphenylglycoluril). Both the halomercuri-pyrimidine nucleoside or nucleotide and the oxidizing agent must be employed in molar excess with respect to the iodide ion.
  • Water-insoluble oxidizing agents are preferred because the excess agent is removed from the aqueous medium after reaction completion in the same filtration step by which the excess halomercuri-pyrimidine nucleoside or nucleotide is removed, thus simplifying still more the subsequent high performance liquid chromatography separation used to remove the small amounts of water-soluble by-products present.
  • the amount of excess of these reagents is not critical, but it is usually convenient and desirable to employ at least 1800 molar excess of each, with respect to iodide ion. Larger excesses are limited only by economics and convenience.
  • the concentration of iodide ion in the aqueous reaction medium is not critical and it may range from 0.1 mCi/mL to 100 mCi/mL, preferably from 0.1 mCi/mL to 10 mCi/mL.
  • the reaction may be carried out at temperatures up to 100°C but optimum results are obtained at 20°-30°C for 1 to 3 hours. Longer or shorter times may be employed at different temperatures and/or iodide concentrations if desired.
  • 2'-Deoxyuridine (0.50 g, 2.20 mmol) was dissolved in 2 mL water and the solution was heated to 50°C.
  • mercuric acetate (0.74 g, 2.32 mmol) in 3 mL water was added.
  • the mixture was brought to 50°C and an additional 1 mL water was added.
  • the reaction was allowed to proceed for 2.5 h at 50°C resulting in a thick white suspension.
  • the heating bath was removed and the mixture cooled to about 40oC.
  • Sodium chloride (0.32 g, 5.45 mmol) in 1 mL water was added to the reaction mixture, and it was stirred for 1 hour.
  • the suspension was filtered, and the white precipitate was washed successively with 0.5 mL 0.1 M NaCl, 0.5 mL water, 0.5 mL 95% ethanol and 0.5 mL. diethyl ether.
  • the precipitate was dried in vacuo at about 60°C for 24 hours giving 0.59 g (57.7%)
  • 5-chloromercuri-2'-deoxyuridine mp. 210-211°C with decomposition (lit. mp. 210.5-211°C; Bergstrom, 1977); 'Hnmr (1 M NaCN/D 2 O) 2.35 ppm. (2H, m, C2'H 2 ), 3.85 ppm. (2H, m, C5'H 2 ). 4.01 ppm. (1H, m, C3'H), 4.46 ppm. (1H, m, C4'H), 6.33 ppm. (1H, t, Cl'H), 7.72 ppm. (1H, s, C6H).
  • Example 5 Preparation of 5-[ 125 I]iodo-2'-deoxyuridine ([ 125 I]IUdR) The radioiodination of 5-fluoro-2'-deoxyuridine was conducted by substituting 8.6 ⁇ mol of it for the 5-chloromercuri-2'-deoxyuridine of Example 4. Approximately 100% of the radioactivity was recovered in the filtrate; the yield of [ 125 I]IUdR was about 50% and the remainder of the radioactivity was recovered in the sodium iodide fraction.
  • Radioiodinated pyrimidine nucleosides such as 5-iodo-2'-deoxyuridine have been used for many years to label the DNA of proliferating cells in studies of tumor transplantation and of DNA structure among other uses.
  • Radioiodination methods for making such compounds have included electrophilic substitution of hydrogen in the pyrimidine ring by reacting water-soluble pyrimidine nucleosides in aqueous solution with sodium iodide and nitric acid as described by Keough et al., J. Labelled Compd. Radiopharm., Vol. 14, pp. 83-90 (1978) and with sodium iodide and chloramine-T as described by Bakker et al., Int. J. Appl. Radiat.
  • the process of the present invention can be applied to any water-insoluble halomercuri-pyrimidine nucleoside such as 5-chloromercuri cytidine, 5-chloromercuri-2'-deoxycytidine, 5-chloromercuri uridine, 5-chloromercuri-2'-deoxyuridine, or water-insoluble halomercuri-pyrimidine nucleotide suchas 5-chloromercuri-cytidine-5'-mono-, di, or tri-phosphate, 5-chloromercuri-2'-deoxycytidine-5'-mono-, di-, or tri-phosphate, 5-chloromercuri-uridine-5'-mono-, di-, or tri-phosphate, or 5-chloromercuri-2'-deoxyuridine-5'-mono-, di-, or tri-phosphate; the corresponding 5-fluoromercuri compounds, and the like may also be used.
  • the water-insoluble nucleosides and nucleotides can
  • the radioactive iodide ion may be employed in the form of any water-soluble salt, e.g. an alkali metal salt such as the sodium salt of 123 I, 125 I, 131 I, preferably in carrier-free form.
  • an alkali metal salt such as the sodium salt of 123 I, 125 I, 131 I, preferably in carrier-free form.
  • Water-insoluble oxidizing agents are preferred because the excess agent is removed from the aqueous medium after reaction completion in the same filtration step by which the excess halomercuri-pyrimidine nucleoside or nucleotide is removed, thus simplifying still more the subsequent high performance liquid chromatography separation used to remove the small amounts of water-soluble by-products present.
  • the amount of excess of these reagents is not critical, but it is usually convenient and desirable to employ at least 1800 molar excess of each, with respect to iodide ion. Larger excesses are limited only by economics and convenience.
  • the concentration of iodide ion in the aqueous reaction medium is not critical and it may range from 0.1 mCi/mL to 100 mCi/mL, preferably from 0.1 mCi/mL to 10 mCi/mL.
  • the reaction may be carried out at temperatures up to 100oC but optimum results are obtained at 20°-30°C for 1 to 3 hours. Longer or shorter times may be employed at different temperatures and/or iodide concentrations if desired.
  • 2' -Deoxyuridine (0.50 g, 2.20 mmol) was dissolved in 2 mL water and the solution was heated to 50°C.
  • mercuric acetate (0.74 g, 2.32 mmol) in 3 mL water was added.
  • the mixture was brought to 50°C and an additional 1 mL water was added.
  • the reaction was allowed to proceed for 2.5 h at 50°C resulting in a thick white suspension.
  • the heating bath was removed and the mixture cooled to about 40°C.
  • Sodium chloride (0.32 g, 5.45 mmol) in 1 mL water was added to the reaction mixture, and it was stirred for 1 hour.
  • the suspension was filtered, and the white precipitate was washed successively with 0.5 mL 0.1 M NaCl, 0.5 mL water, 0.5 mL 95% ethanol and 0.5 mL diethyl ether.
  • the precipitate was dried in vacuo at about 60°C for 24 hours giving 0.59 g (57.7%)
  • 5-chloromercuri-2'-deoxyuridine mp. 210-211°C with decomposition (lit. mp. 210.5-211°C; Bergstrom, 1977); 'Hnmr (1 M NaCN/D 2 O) 2.35 ppm. (2H, m, C2'H 2 ), 3.85 ppm. (2H, m, C5'H 2 ), 4.01 ppm. (1H, m, C3'H), 4.46 ppm. (1H, m, C4'H), 6.33 ppm. (1H, t, Cl ⁇ ), 7.72 ppm. (1H, s, C6H).
  • Example 5 Preparation of 5-[ 125 I]iodo-2'-deoxyuridine ([ 125 I]IUdR) The radioiodination of 5-fluoro-2'-deoxyuridine was conducted by substituting 8.6 ⁇ mol of it for the 5-chloromercuri-2'-deoxyuridine of Example 4. Approximately 100% of the radioactivity was recovered in the filtrate; the yield of [ 125 I]IUdR was about 50% and the remainder of the radioactivity was recovered in the sodium iodide fraction.

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Abstract

The method of making radioiodinated pyrimidine nucleoside or nucleotide which comprises contacting a water-insoluble halomercuri pyrimidine nucleoside or nucleotide with an aqueous medium containing a dissolved radioactive iodide ion and an oxidizing agent, the molar amounts of said nucleoside or nucleotide and said oxidizing agent being in excess of the molar amount of said iodide, whereby water-soluble radioactive iodinated pyrimidine nucleoside or nucleotide is formed in solution, and separating residual water-insoluble halomercuri pyrimidine nucleoside or nucleotide from said solution.

Description

METHOD OF MAKING RADIOIODINATED PYRIMIDINE NUCLEOSIDE OR NUCLEOTIDE This invention relates to a method of making radioiodinated pyrimidine nucleosides and nucleotides and pertains more specifically to a heterogeneous phase reaction for making the desired compounds in a form which is readily purifiable, for example by a simple HPLC procedure.
Radioiodinated pyrimidine nucleosides such as 5-iodo-2'-deoxyuridine have, been used for many years to label the DNA of proliferating cells in studies of tumor transplantation and of DNA structure among other uses. Radioiodination methods for making such compounds have included electrophilic substitution of hydrogen in the pyrimidine ring by reacting water-soluble pyrimidine nucleosides in aqueous solution with sodium iodide and nitric acid as described by Keough et al., J. Labelled Compd. Radiopharm., Vol. 14, pp. 83-90 (1978) and with sodium iodide and chloramine-T as described by Bakker et al., Int. J. Appl. Radiat. Isot., Vol. 32, pp. 176-178 (1981). Although the radiochemical yields in. these processes are high, and satisfactory separation of the product from residual sodium iodide can usually be achieved by chromatography, complete removal of unreacted pyrimidine nucleoside is very difficult because of the more than 20, 000-fold excess of this starting material used in the synthesis and requires complicated and lengthy procedures.
There has now been discovered a facile procedure for the preparation of radioiodinated pyrimidine nucleosides and nucleotides which comprises contacting a water-insoluble halomercuri-pyrimidine nucleoside or nucleotide with an aqueous medium containing a dissolved radioactive iodide ion and an oxidizing agent, the molar amount of said nucleoside or nucleotide being in excess of the molar amount of said iodide, whereby water-soluble radioactive iodinated pyrimidine nucleoside or nucleotide is formed in solution, and separating residual water-insoluble halomercuri-pyrimidine nucleoside or nucleotide from said solution. The separation can readily be carried out by conventional filtration procedures. The method is suitable for no-carrier-added syntheses and, following the separation step, requires only a minimal purification process, for example, by conventional HPLC procedures, to produce a product of extremely high purity.
The process of the present invention can be applied to any water-insoluble halomercuri-pyrimidine nucleoside such as 5-chloromercuri cytidine, 5-chloromercuri-2'-deoxycytidine, 5-chloromercuri uridine, 5-chloromercuri-2'-deoxyuridine, or water-insoluble halomercuri-pyrimidine nucleotide" such as 5-chloromercuri-cytidine-5'-mono-, di, or tri-phosphate, 5-chloromercuri-2'-deoxycytidine-5'-mono-, di-, or tri-phosphate, 5-chloromercuri-uridine-5'-mono-, di-, or tri-phosphate, or 5-chloromercuri-2'-deoxyuridine-5'-mono-, di-, or tri-phosphate; the corresponding 5-fluoromercuri compounds, and the like may also be used. The water-insoluble nucleosides and nucleotides can be made by well-known procedures as described, for example, in Bergstrom et al., J.
Carbohyr., Nucleosides, Nucleotides, Vol. 4, pp. 257-269 (1977).
The radioactive iodide ion may be employed in the form of any water-soluble salt, e.g. an alkali metal salt such as the sodium salt of 123I, 125I, 131I, preferably in carrier-free form.
The oxidizing agent used may be either water-soluble as in the case of Chloramine-T or nitric acid; or it may be water-insoluble as in the case of iodogen (1,3,4,6-tetrachloro-3α, 6α-diphenylglycoluril). Both the halomercuri-pyrimidine nucleoside or nucleotide and the oxidizing agent must be employed in molar excess with respect to the iodide ion. Water-insoluble oxidizing agents are preferred because the excess agent is removed from the aqueous medium after reaction completion in the same filtration step by which the excess halomercuri-pyrimidine nucleoside or nucleotide is removed, thus simplifying still more the subsequent high performance liquid chromatography separation used to remove the small amounts of water-soluble by-products present. The amount of excess of these reagents is not critical, but it is usually convenient and desirable to employ at least 1800 molar excess of each, with respect to iodide ion. Larger excesses are limited only by economics and convenience. The concentration of iodide ion in the aqueous reaction medium is not critical and it may range from 0.1 mCi/mL to 100 mCi/mL, preferably from 0.1 mCi/mL to 10 mCi/mL. The reaction may be carried out at temperatures up to 100°C but optimum results are obtained at 20°-30°C for 1 to 3 hours. Longer or shorter times may be employed at different temperatures and/or iodide concentrations if desired. After filtration of the reaction mixture to remove excess halomercuri-pyrimidine nucleoside or nucleotide and excess oxidizing agent (when a water-insoluble oxidizing agent is used), the reaction mixture is subjected to high performance liquid chromatography preferably on a reverse phase column (Bonda Pak C18) using methyl alcohol/distilled water 20/80) as eluant. Eluates can be assayed by ultraviolet absorption and by gamma ray detection. The following specific examples are intended to illustrate more fully the nature of the invention without acting as a limitation upon its scope. Example 1 Preparation of 5-chloromercuri-2'-deoxyuridine
2'-Deoxyuridine (0.50 g, 2.20 mmol) was dissolved in 2 mL water and the solution was heated to 50°C. To this solution mercuric acetate (0.74 g, 2.32 mmol) in 3 mL water was added. The mixture was brought to 50°C and an additional 1 mL water was added. The reaction was allowed to proceed for 2.5 h at 50°C resulting in a thick white suspension. The heating bath was removed and the mixture cooled to about 40ºC. Sodium chloride (0.32 g, 5.45 mmol) in 1 mL water was added to the reaction mixture, and it was stirred for 1 hour. The suspension was filtered, and the white precipitate was washed successively with 0.5 mL 0.1 M NaCl, 0.5 mL water, 0.5 mL 95% ethanol and 0.5 mL. diethyl ether. The precipitate was dried in vacuo at about 60°C for 24 hours giving 0.59 g (57.7%)
5-chloromercuri-2'-deoxyuridine: mp. 210-211°C with decomposition (lit. mp. 210.5-211°C; Bergstrom, 1977); 'Hnmr (1 M NaCN/D2O) 2.35 ppm. (2H, m, C2'H2), 3.85 ppm. (2H, m, C5'H2). 4.01 ppm. (1H, m, C3'H), 4.46 ppm. (1H, m, C4'H), 6.33 ppm. (1H, t, Cl'H), 7.72 ppm. (1H, s, C6H).
Example 2
Preparation of 5-fluoromercuri-2'-deoxyuridine 2'-Deoxyuridine (0.50 g, 2.20 mmol) was reacted with mercuric acetate (0.74 g, 2.32 mmol) as described in Example 1 above. Sodium fluoride (0.23 g, 5.45 mmol) in 1 mL water was added after the reaction mixture had cooled to about 40°C. The suspension was stirred for 1 hour and filtered. The precipitate was washed successively with 1 mL 0.1 M sodium fluoride, 1 mL water, 0.5 mL 95% ethanol and 0.5 mL diethyl. ether. Drying in vacuo at 60°C gave 0.48 g (49.1%) 5-fluolomercuri-2'-deoxyuridine: mp. 250-257°C with decomposition; 'Hnmr (1 M NaCN/D2O) 2.38 ppm. (2H, t, C2'H2), 3.84 ppm. (2H, m, C5'H2), 4.00 ppm. (1H, m,
C3'H), 4.47 ppm. (1H, m, C4'H), 6.35 ppm. (1H, t, Cl'H), 7.51 ppm (1H, s, C6H). Example 3 Preparation of 5-iodo-2'-deoxyuridine (IUdR) Iodogen (10 mg, 23.1 μmol) and freshly prepared
5-chloromercuri-2'-deoxyuridine (10 mg, 21.6 μmol) were suspended in 0.4 mL water. To this mixture a solution of sodium iodide (3 mg, 20 μmol) in 0.4 mL water was added. The mixture was allowed to react at room temperature for 24 hours during which time it was vigorously stirred. Filtration of the mixture through a 0.22 m Millex filter gave 0.78 mL of clear solution. This was chromatographed by HPLC giving 2.9 mg (41%) IUdR with a retention time (RT) of 7.1 min (identical to an authentic sample). The HPLC revealed the presence of two other components (RT = 2.2 min, 3.31%; RT = 16.9 min, 9.95%) (Fig. 1). The first peak was also observed when a solution of pure NaI was injected; the last peak was identified as some oxidized form of iodine generated from NaI in the presence of Iodogen, presumably ICl). This latter peak was not observed during the no-carrier-added radioiodination. The synthesis was repeated several times varying the reaction time and the ratio of the reagents. The crude filtrate (prior to HPLC) from one such experiment was analyzed for mercury and 0.2 g/mL was found.
The retention time of Iodogen was established as follows: a saturated solution of Iodogen in methanol was prepared and chromatographed (15 minutes isocratic H2O/CH3OH, 80/20 by volume, followed by a linear gradient to 100% methanol in 10 min); RT of Iodogen = 29 minutes. Sodium iodide was added to the saturated solution of Iodogen, and the mixture was allowed to react for 3 hours after which it was quenched with
Na2S2O5. The filtrate was chromatographed as described for Iodogen; RT of the by-product = 3.2 minutes.
Example 4 Preparation of 5-[125I]iodo-2'-deoxyuridine ( [125I]IUdR) To the dry mixture of freshly prepared
5-chloromercuri-2'-deoxyuridine (4 mg, 8.6 μmol) and Iodogen (4 mg, 9.3 μmol) was added 1.4 mCi sodium [125I] iodide in 0.3 mL water. The mixture was stirred in a closed 2-mL reaction vial at room temperature for 2 hours. The suspension was withdrawn from the reaction vessel into a 5-mL syringe and filtered through a 0.22 μm Millex filter. The reaction vial and filter were washed 4 times with 0.2 mL water. The combined filtrates were injected into the HPLC and the radioactive content of each fraction determined. Fractions from the peak with an RT = 7.1 minutes, corresponding to that of an authentic sample, afforded 5-[125I]iodo-2'-deoxyuridine in 57.1% radiochemical yield (0.8 mCi). The radiochemical purity of the crude C125I]IUdR in the filtrate was 99.1%, sodium
[125I] iodide accounted for the remaining 0.9% of the radioactivity (RT = 2.2 minutes).
There is shown in Table 1 below a summary of yield and purity of [125I]IUdR obtained by varying the conditions of the foregoing example.
TABLE 1
Summary of Yields and Purity of [ 125 I ] IUdR obtained
Under Different Reaction Conditions
Reaction time Percent Percent
Solvent (h) ClHgUdR: Iodogena purity yield
water 1 3:3 77.0 22.4 water 3 10:2.5 97.8 36.7 water 1 10:10 84.0 44.0 water 2c 10:10 99.1±0.4 54.8±1.6
mg/mL:mg/mL
four runs
Example 5 Preparation of 5-[125I]iodo-2'-deoxyuridine ([125I]IUdR) The radioiodination of 5-fluoro-2'-deoxyuridine was conducted by substituting 8.6 μmol of it for the 5-chloromercuri-2'-deoxyuridine of Example 4. Approximately 100% of the radioactivity was recovered in the filtrate; the yield of [125I]IUdR was about 50% and the remainder of the radioactivity was recovered in the sodium iodide fraction. Example 6 Preparation of 5-[123I]iodo-2'-deoxyuridine ([123I]IUdR) To a dry mixture of 5-chloromecuri-2'-deoxyuridine (4 mg, 8.6 mol) and Iodogen (4 mg, 9.3 mol) was added 2.1 mCi sodium [123I] iodide in 0.3 mL water. The pH of the sodium iodide solution was adjusted to about 7 using 0.1 M acetic acid. The mixture was stirred in a closed 2-mL reaction vial at room temperature for 3 hours. The suspension was withdrawn from the reaction vessel into a 5-mL syringe and filtered through a 0.22 m Millex filter. The reaction vial and the filter were washed 4 times with 0.2 mL water. The combined filtrates were injected into the HPLC, and the fraction were collected and counted in a dose calibrator. The radioactive fractions which corresponded to an authentic sample (RT = 7.1 minutes) afforded 5-[123I]iodo-2'-deoxyuridine in 65.7% radiochemical yield (1.37 mCi). The radiochemical purity of the crude [123I]IUdR in the filtrate was 98%. Sodium [123I] iodide accounted for 1.2% of the radioactivity (RT = 2.2 minutes), and the remaining 0.8% was associated with unidentified species with RT = 4.1 minutes.
Similar results can be obtained when other water-insoluble halomercuri pyrimidine nucleosides or nucleotides are employed. What is claimed is:
Internationa] Bureau
INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
(51) International Patent Classification **■ (11) International Publication Number: WO 89/ 07 C07H 1/00 Al (43) International Publication Date : 10 August 1989 ( 10.08.
(21) International Application Number: PCT/US89/00358 (81) Designated States: AT (European patent), BE (E pean patent), CH (European patent), DE (Europ
(22) International Filing Date: 27 January 1989 (27.01.89) patent), FR (European patent), GB (European tent), IT (European patent), JP, LU (European tent), NL (European patent), SE (European paten
(31) Priority Application Number : 150, 133
(32) Priority Date: 29 January 1988 (29.01.88) Published
With international search report.
(33) Priority Country: US With amended claims.
(71) Applicant: PRESIDENT AND FELLOWS OF HAR¬
VARD COLLEGE [US/US]; 17 Quincy Street, Cambridge, MA 02138 (US).
(72) Inventors: KASSIS, Amin, I. ; 57 Stockdale Road,
Needham, MA 02192 (US). BARANOWSKA-KORTYLEWICZ, Janina ; 12 Stoneholm, No. 319, Boston, MA 02115 (US).
(74) Agent: FURLONG, Robert, W.; Fish & Richardson, One Financial Center, Suite 2500, Boston, MA 02111-2658 (US).
(54) Title: METHOD OF MAKING RADIOIODINATED PYRIMIDINE
(57) Abstract
The method of making radioiodinated pyrimidine nucleoside or nucleotide which comprises contacting a water-i soluble halomercuri pyrimidine nucleoside or nucleotide with an aqueous medium containing a dissolved radioactive i dide ion and an oxidizing agent, the molar amounts of said nucleoside or nucleotide and said oxidizing agent being excess of the molar amount of said iodide, whereby water-soluble radioactive iodinated pyrimidine nucleoside or nucle tide is formed in solution, and separating residual water-insoluble halomercuri pyrimidine nucleoside or nucleotide fro said solution.
FOR THE PURPOSES OFINFORMAHON ONLY
Codes used to identify States party to the PCT on the front pages of pamphlets publishing international applications under the PCT.
AT Austria FR France ML Mali
AC Australia GA Gabon MR Mauritania
BB Barbados GB United Kingdom MW Malawi
BE Belgium HU Hungary NL Netherlands
BG Bulgaria IT Italy NO Norway
BJ Benin P Japan RO Romania
BR Brazil KP Democratic People's Republic SD Sudan
CF Central African Republic of Korea SE Sweden
CG Congo KR Republic of Korea SN Senegal
CH Switzerland LI Liechtenstein SU Soviet Union
CM Cameroon LK Sri Lanka TD Chad
DE Germany, Federal Republic of LU Luxembourg TG Togo
DK Denmark MC Monaco US United States of America
FT Finland MG Madagascar
METHOD OF MAKING RADIOIODINATED PYRIMIDINE NUCLEOSIDE OR NUCLEOTIDE This invention relates to a method of making radioiodinated pyrimidine nucleosides and nucleotides and pertains more specifically to a heterogeneous phase reaction for making the desired compounds in a form which is readily purifiable, for example by a simple HPLC procedure.
Radioiodinated pyrimidine nucleosides such as 5-iodo-2'-deoxyuridine have been used for many years to label the DNA of proliferating cells in studies of tumor transplantation and of DNA structure among other uses. Radioiodination methods for making such compounds have included electrophilic substitution of hydrogen in the pyrimidine ring by reacting water-soluble pyrimidine nucleosides in aqueous solution with sodium iodide and nitric acid as described by Keough et al., J. Labelled Compd. Radiopharm., Vol. 14, pp. 83-90 (1978) and with sodium iodide and chloramine-T as described by Bakker et al., Int. J. Appl. Radiat. Isot., Vol. 32, pp. 176-178 (1981). Although the radiochemical yields in these processes are high, and satisfactory separation of the product from residual sodium iodide can usually be achieved by chromatography, complete removal of unreacted pyrimidine nucleoside is very difficult because of the more than 20,000-fold excess of this starting material used in the synthesis and requires complicated and lengthy procedures.
There has now been discovered a facile procedure for the preparation of radioiodinated pyrimidine nucleosides and nucleotides which comprises contacting a water-insoluble halomercuri-pyrimidine nucleoside or nucleotide with an aqueous medium containing a dissolved radioactive iodide ion and an oxidizing agent, the molar amount of said nucleoside or nucleotide being in excess of the molar amount of said iodide, whereby water-soluble radioactive iodinated pyrimidine nucleoside or nucleotide is formed in solution, and separating residual water-insoluble halomercuri-pyrimidine nucleoside or nucleotide from said solution. The separation can readily be carried out by conventional filtration procedures. The method is suitable for no-carrier-added syntheses and, following the separation step, requires only a minimal purification process, for example, by conventional HPLC procedures, to produce a product of extremely high purity.
The process of the present invention can be applied to any water-insoluble halomercuri-pyrimidine nucleoside such as 5-chloromercuri cytidine, 5-chloromercuri-2'-deoxycytidine, 5-chloromercuri uridine, 5-chloromercuri-2'-deoxyuridine, or water-insoluble halomercuri-pyrimidine nucleotide suchas 5-chloromercuri-cytidine-5'-mono-, di, or tri-phosphate, 5-chloromercuri-2'-deoxycytidine-5'-mono-, di-, or tri-phosphate, 5-chloromercuri-uridine-5'-mono-, di-, or tri-phosphate, or 5-chloromercuri-2'-deoxyuridine-5'-mono-, di-, or tri-phosphate; the corresponding 5-fluoromercuri compounds, and the like may also be used. The water-insoluble nucleosides and nucleotides can be made by well-known procedures as described, for example, in Bergstrom et al., J.
Carbohyr., Nucleosides, Nucleotides, Vol. 4, pp. 257-269 (1977).
The radioactive iodide ion may be employed in the form of any water-soluble salt, e.g. an alkali metal salt such as the sodium salt of 123I, 125I, 131I, preferably in carrier-free form.
The oxidizing agent used may be either water-soluble as in the case of Chloramine-T or nitric acid; or it may be water-insoluble as in the case of Iodogen (1,3,4,6-tetrachloro-3α, 6α-diphenylglycoluril). Both the halomercuri-pyrimidine nucleoside or nucleotide and the oxidizing agent must be employed in molar excess with respect to the iodide ion. Water-insoluble oxidizing agents are preferred because the excess agent is removed from the aqueous medium after reaction completion in the same filtration step by which the excess halomercuri-pyrimidine nucleoside or nucleotide is removed, thus simplifying still more the subsequent high performance liquid chromatography separation used to remove the small amounts of water-soluble by-products present. The amount of excess of these reagents is not critical, but it is usually convenient and desirable to employ at least 1800 molar excess of each, with respect to iodide ion. Larger excesses are limited only by economics and convenience. The concentration of iodide ion in the aqueous reaction medium is not critical and it may range from 0.1 mCi/mL to 100 mCi/mL, preferably from 0.1 mCi/mL to 10 mCi/mL. The reaction may be carried out at temperatures up to 100ºC but optimum results are obtained at 20°-30°C for 1 to 3 hours. Longer or shorter times may be employed at different temperatures and/or iodide concentrations if desired. After filtration of the reaction mixture to remove excess halomercuri-pyrimidine nucleoside or nucleotide and excess oxidizing agent (when a water-insoluble oxidizing agent is used), the reaction mixture is subjected to high performance liquid chromatography preferably on a reverse phase column (Bonda Pak C18) using methyl alcohol/distilled water 20/80) as eluant. Eluates can be assayed by ultraviolet absorption and by gamma ray detection. The following specific examples are intended to illustrate more fully the nature of the invention without acting as a limitation upon its scope. Example 1 Preparation of 5-chloromercuri-2'-deoxyuridine
2' -Deoxyuridine (0.50 g, 2.20 mmol) was dissolved in 2 mL water and the solution was heated to 50°C. To this solution mercuric acetate (0.74 g, 2.32 mmol) in 3 mL water was added. The mixture was brought to 50°C and an additional 1 mL water was added. The reaction was allowed to proceed for 2.5 h at 50°C resulting in a thick white suspension. The heating bath was removed and the mixture cooled to about 40°C. Sodium chloride (0.32 g, 5.45 mmol) in 1 mL water was added to the reaction mixture, and it was stirred for 1 hour. The suspension was filtered, and the white precipitate was washed successively with 0.5 mL 0.1 M NaCl, 0.5 mL water, 0.5 mL 95% ethanol and 0.5 mL diethyl ether. The precipitate was dried in vacuo at about 60°C for 24 hours giving 0.59 g (57.7%)
5-chloromercuri-2'-deoxyuridine: mp. 210-211°C with decomposition (lit. mp. 210.5-211°C; Bergstrom, 1977); 'Hnmr (1 M NaCN/D2O) 2.35 ppm. (2H, m, C2'H2), 3.85 ppm. (2H, m, C5'H2), 4.01 ppm. (1H, m, C3'H), 4.46 ppm. (1H, m, C4'H), 6.33 ppm. (1H, t, Cl Η), 7.72 ppm. (1H, s, C6H).
Example 2
Preparation of 5-fluoromercuri-2'-deoxyuridine
2' -Deoxyuridine (0.50 g, 2.20 mmol) was reacted with mercuric acetate (0.74 g, 2.32 mmol) as described in Example 1 above. Sodium fluoride (0.23 g, 5.45 mmol) in l mL water was added after the reaction mixture had cooled to about 40ºC. The suspension was stirred for 1 hour and filtered. The precipitate was washed successively with 1 mL 0.1 M sodium fluoride, 1 mL water, 0.5 mL 95% ethanol and 0.5 mL diethyl ether. Drying in vacuo at 60°C gave 0.48 g (49.1%) 5-fluoromercuri-2'-deoxyuridine: mp. 250-257°C with decomposition; 'Hnmr (1 M NaCN/D2O) 2.38 ppm. (2H, t, C2'H2), 3.84 ppm. (2H, m, C5'H2), 4.00 ppm. (1H, m,
C3'H), 4.47 ppm. (1H, m, C4'H), 6.35 ppm. (1H, t, Cl'H), 7.51 ppm (1H, s, C6H). Example 3
Preparation of 5-iodo-2'-deoxyuridine (IUdR) Iodogen (10 mg, 23.1 μmol) and freshly prepared
5-chloromercuri-2'-deoxyuridine (10 mg, 21.6 μmol) were suspended in 0.4 mL water. To this mixture a solution of sodium iodide (3 mg, 20 μmol) in 0.4 mL water was added. The mixture was allowed to react at room temperature for 24 hours during which time it was vigorously stirred. Filtration of the mixture through a 0.22 m Millex filter gave 0.78 mL of clear solution. This was chromatographed by HPLC giving 2.9 mg (41%) IUdR with a retention time (RT) of 7.1 min (identical to an authentic sample). The HPLC revealed the presence of two other components (RT = 2.2 min, 3.31%; RT = 16.9 min, 9.95%) (Fig. 1). The first peak was also observed when a solution of pure Nal was injected; the last peak was identified as some oxidized form of iodine generated from Nal in the presence of Iodogen, presumably ICl). This latter peak was not observed during the no-carrier-added radioiodination. The synthesis was repeated several times varying the reaction time and the ratio of the reagents. The crude filtrate (prior to HPLC) from one such experiment was analyzed for mercury and 0.2 g/mL was found.
The retention time of Iodogen was established as follows: a saturated solution of Iodogen in methanol was prepared and chromatographed (15 minutes isocratic H2O/CH3OH, 80/20 by volume, followed by a linear gradient to 100% methanol in 10 min); RT of Iodogen = 29 minutes. Sodium iodide was added to the saturated solution of Iodogen, and the mixture was allowed to react for 3 hours after which it was quenched with
Na2S2O5. The filtrate was chromatographed as described for Iodogen; RT of the by-product = 3.2 minutes.
Example 4 Preparation of 5-[125I]iodo-2'-deoxyuridine ([125I]IUdR) To the dry mixture of freshly prepared
5-chloromercuri-2'-deoxyuridine (4 mg, 8.6 μmol) and Iodogen (4 mg, 9.3 μmol) was added 1.4 mCi sodium [125I] iodide in 0.3 mL water. The mixture was stirred in a closed 2-mL reaction vial at room temperature for 2 hours. The suspension was withdrawn from the reaction vessel into a 5-mL syringe and filtered through a 0.22 μm Millex filter. The reaction vial and filter were washed 4 times with 0.2 mL water. The combined filtrates were injected into the HPLC, and the radioactive content of each fraction determined. Fractions from the peak with an RT = 7.1 minutes, corresponding to that of an authentic sample, afforded 5-[125I]iodo-2'-deoxyuridine in 57.1% radiochemical yield (0.8 mCi). The radiochemical purity of the crude [125I]IUdR in the filtrate was 99.1%, sodium
[125I] iodide accounted for the remaining 0.9% of the radioactivity (RT = 2.2 minutes).
There is shown in Table 1 below a summary of yield and purity of [125I]IUdR obtained by varying the conditions of the foregoing example.
TABLE 1
Summary of Yields and Purity of [125I]IUdR Obtained
Under Different Reaction Conditions
Reaction time Percent Percent
Solvent (h) ClHgUdR: Iodogena purity yield
water 1 3:3 77.0 22.4 water 3 10:2.5 97.8 36.7 water 1 10:10 84.0 44.0 water 2c 10:10 99.1±0, .4 54.8±1.6
a. mg/mL:mg/mL
c. four runs
Example 5 Preparation of 5-[125I]iodo-2'-deoxyuridine ([125I]IUdR) The radioiodination of 5-fluoro-2'-deoxyuridine was conducted by substituting 8.6 μmol of it for the 5-chloromercuri-2'-deoxyuridine of Example 4. Approximately 100% of the radioactivity was recovered in the filtrate; the yield of [125I]IUdR was about 50% and the remainder of the radioactivity was recovered in the sodium iodide fraction. Example 6 Preparation of 5-[123I3]iodo-2'-deoxyuridine ([123I]IUdR) To a dry mixture of 5-chloromecuri-2'-deoxyuridine (4 mg, 8.6 mol) and Iodogen (4 mg, 9.3 mol) was added 2.1 mCi sodium [123I]iodide in 0.3 mL water. The pH of the sodium iodide solution was adjusted to about 7 using 0.1 M acetic acid. The mixture was stirred in a closed 2-mL reaction vial at room temperature for 3 hours. The suspension was withdrawn from the reaction vessel into a 5-mL syringe and filtered through a 0.22 m MiIlex filter. The reaction vial and the filter were washed 4 times with 0.2 mL water. The combined filtrates were injected into the HPLC, and the fraction were collected and counted in a dose calibrator. The radioactive fractions which corresponded to an authentic sample (RT = 7.1 minutes) afforded 5-[123I]iodo-2'-deoxyuridine in 65.7% radiochemical yield (1.37 mCi). The radiochemical purity of the crude [123I]IUdR in the filtrate was 98%. Sodium [123I] iodide accounted for 1.2% of the radioactivity (RT = 2.2 minutes), and the remaining 0.8% was associated with unidentified species with RT = 4.1 minutes.
Similar results can be obtained when other water-insoluble halomercuri pyrimidine nucleosides or nucleotides are employed. What is claimed is:

Claims

1. The method of making radioiodinated pyrimidine nucleoside or nucleotide which comprises contacting a water-insoluble halomercuri pyrimidine nucleoside or nucleotide with an aqueous medium containing a dissolved radioactive iodide ion and an oxidizing agent, the molar amounts of said nucleoside or nucleotide and said oxidizing agent being in excess of the molar amount of said iodide, whereby water-soluble radioactive iodinated pyrimidine nucleoside or nucleotide is formed in solution, and separating residual water-insoluble material including halomercuri pyrimidine nucleoside or nucleotide from said solution.
2. The method as claimed in claim 1 in which said insoluble nucleoside or nucleotide is 5-chloromercuri pyrimidine nucleoside or nucleotide.
3. The method as claimed in claim 2 in which said insoluble nucleoside is 5-chloromercuri-2'-deoxyuridine.
4. The method as claimed in claim 1 in which said insoluble nucleoside or nucleotide is fluoromercuri pyrimidine nucleoside or nucleotide.
5. The method as claimed in claim 4 in which said insoluble nucleoside is 5-fluoromercuri-2'-deoxyuridine.
6. The method as claimed in claim 1 in which said oxidizing agent is water-insoluble.
7. The method as claimed in claim 1 in which said oxidizing agent is Iodogen.
8. The method as claimed in claim 2 in which said oxidizing agent is water-insoluble.
9. The method as claimed in claim 2 in which said oxidizing agent is Iodogen.
10. The method as claimed in claim 3 in which said oxidizing agent is water-insoluble.
11. The method as claimed in claim 3 in which said oxidizing agent is Iodogen.
12. The method as claimed in claim 4 in which said oxidizing agent is water-insoluble.
13. The method as claimed in claim 4 in which said oxidizing agent is Iodogen.
14. The method as claimed in claim 5 in which said oxidizing agent is water-insoluble.
15. The method as claimed in claim 5 in which said oxidizing agent is Iodogen.
PCT/US1989/000358 1988-01-29 1989-01-27 Method of making radioiodinated pyrimidine Ceased WO1989007106A1 (en)

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EP0428623A4 (en) * 1988-08-10 1993-12-08 Stephen Leslie Sacks Production of radioiodinated 1--g(b)-d-arabinofuranosyl)-5(e)-(2-iodovinyl)uracil, and uses thereof, and related analogues incorporating alternative halogen radionuclides, the general radiohalogenation precursors, 1-(2,3,5-tri-o-acetyl--g(b)-d-arabinofuranosyl)-5(z and e)-(2-trimethylsilylvinyl)urac
US5077034A (en) * 1990-03-30 1991-12-31 The President And Fellows Of Harvard College Treatment of tumors with 5-radioiodo-2'-deoxyuridine
US5468853A (en) * 1993-12-30 1995-11-21 Board Of Regents University Of Nebraska Synthesis of 5-radiohalo-2'-deoxyuridine
US5720935A (en) * 1995-06-09 1998-02-24 President & Fellows Of Harvard College Rapid synthesis of radiolabeled pyrimidine nucleosides or nucleotides from stannyl precursors
US5811073A (en) * 1995-06-19 1998-09-22 President And Fellows Of Harvard College Method for radioisotopic detection and localization of inflammation in a host
US7238338B1 (en) 2001-06-22 2007-07-03 Triumf System and method for the large scale labeling of compounds with radiohalogens
US8597613B2 (en) * 2004-07-02 2013-12-03 Iso-Tex Diagnostics, Inc Radiolabeled lymphatic staining agents and methods for making

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