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  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C229/00—Compounds containing amino and carboxyl groups bound to the same carbon skeleton
  • C07C229/02—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton
  • C07C229/04—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated
  • C07C229/06—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated having only one amino and one carboxyl group bound to the carbon skeleton
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  • C07F13/00—Compounds containing elements of Groups 7 or 17 of the Periodic Table
  • C07F13/005—Compounds without a metal-carbon linkage
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K51/00—Preparations containing radioactive substances for use in therapy or testing in vivo
  • A61K51/02—Preparations containing radioactive substances for use in therapy or testing in vivo characterised by the carrier, i.e. characterised by the agent or material covalently linked or complexing the radioactive nucleus
  • A61K51/04—Organic compounds
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K51/00—Preparations containing radioactive substances for use in therapy or testing in vivo
  • A61K51/02—Preparations containing radioactive substances for use in therapy or testing in vivo characterised by the carrier, i.e. characterised by the agent or material covalently linked or complexing the radioactive nucleus
  • A61K51/04—Organic compounds
  • A61K51/0474—Organic compounds complexes or complex-forming compounds, i.e. wherein a radioactive metal (e.g. 111In3+) is complexed or chelated by, e.g. a N2S2, N3S, NS3, N4 chelating group
  • A61K51/0478—Organic compounds complexes or complex-forming compounds, i.e. wherein a radioactive metal (e.g. 111In3+) is complexed or chelated by, e.g. a N2S2, N3S, NS3, N4 chelating group complexes from non-cyclic ligands, e.g. EDTA, MAG3
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K51/00—Preparations containing radioactive substances for use in therapy or testing in vivo
  • A61K51/02—Preparations containing radioactive substances for use in therapy or testing in vivo characterised by the carrier, i.e. characterised by the agent or material covalently linked or complexing the radioactive nucleus
  • A61K51/04—Organic compounds
  • A61K51/0474—Organic compounds complexes or complex-forming compounds, i.e. wherein a radioactive metal (e.g. 111In3+) is complexed or chelated by, e.g. a N2S2, N3S, NS3, N4 chelating group
  • A61K51/0487—Metallocenes, i.e. complexes based on a radioactive metal complexed by two cyclopentadienyl anions
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  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C229/00—Compounds containing amino and carboxyl groups bound to the same carbon skeleton
  • C07C229/02—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton
  • C07C229/04—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated
  • C07C229/20—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated the carbon skeleton being further substituted by halogen atoms or by nitro or nitroso groups
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C229/00—Compounds containing amino and carboxyl groups bound to the same carbon skeleton
  • C07C229/02—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton
  • C07C229/04—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated
  • C07C229/22—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to acyclic carbon atoms of the same carbon skeleton the carbon skeleton being acyclic and saturated the carbon skeleton being further substituted by oxygen atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
  • C07B2200/00—Indexing scheme relating to specific properties of organic compounds
  • C07B2200/05—Isotopically modified compounds, e.g. labelled

Definitions

• radiolabeled amino acids for use as metabolic tracers to image tumors using positron emission tomography (PET) and single photon emission computed tomography (SPECT) has been underway for two decades.
• PET positron emission tomography
• SPECT single photon emission computed tomography
• conventional imaging methods such as CT and MRI do not reliably distinguish residual or recurring tumor from tissue injury due to the intervention and are not optimal for monitoring the effectiveness of treatment or detecting tumor recurrence [Buonocore, E (1992), Clinical Positron Emission Tomography. Mosby-Year Book, Inc. St. Louis, MO, pp 17-22; Langleben, DD etal. (2000), J. Nucl. Med. 41:1861-1867].
• the leading PET agent for diagnosis and imaging of neoplasms also has limitations in the imaging of brain tumors.
• Normal brain cortical tissue shows high [ 18 F]FDG uptake as does inflammatory tissue which can occur after radiation or surgical therapy; these factors can complicate the interpretation of images acquired with [ 18 F]FDG [Griffeth, LK et al. (1993), Radiology. 186:37-44; Conti, PS (1995)].
• a number of amino acids including [ n C] ⁇ -aminoisobutyric acid (AIB), L- [ n C]methionine (Met), L-[ 18 F]fluoro- ⁇ -methyl tyrosine, 0-(2-[ 18 F]fluoroethyl)tyrosine and tr n5-l-amino-3-[ 18 F]fluorocyclobutyl-l-carboxylic acid (FACBC), have been successfully used for PET tumor imaging in humans [Jager, PL et al. (2001), J. Nucl. Med. 42:432-445; Shoup, TM et al. (1999), J. Nucl. Med. 40:331-338].
• N-MeAIB shows even more selectivity for the A-type amino acid transport system than AIB [Shotwell, MA et al. (1983), Biochim. Biophys. Ada. 737:267-84].
• N-MeAIB has been radiolabeled with carbon-11 and is metabolically stable in humans [ ⁇ agren, K et al. (2000), J. Labelled Cpd. Radiopharm. 43: 1013-1021].
• fluorinated analogs of AIB suitable for labeling with 18 F and use in PET imaging. These agents are expected to demonstrate metabolic stability in vivo due to their ⁇ , ⁇ -dialkyl branching and to have the potential for remote distribution due to the 110 minute half-life of 18 F versus 20 minutes for n C.
• FAMP 2-amino-3-fluoro-2-methylpropanoic acid
• N-MeFAMP 3-fluoro-2-methyl-2- (methylamino)propanoic acid
• fluorinated analogs of AIB and N-methyl AIB respectively.
• the invention provides novel amino acid compounds of use in detecting and evaluating brain and body tumors.
• These compounds combine the advantageous properties of ⁇ -aminoisobutyric acid (AJB) analogs namely, their rapid uptake and prolonged retention in tumors with the properties of halogen substituents, including certain useful halogen isotopes such as fluorine-18, iodine-123, isodine-124, iodine-125, iodine-131, bromine-75, bromine- 76, bromine-77, bromine-82, astatine-210. astatine-211, and other astatine isotopes.
• the compounds can be labeled with technetium and rhenium isotopes using known chelation complexes.
• the invention features amino acid compounds that have a high specificity for target sites when administered to a subject in vivo.
• Preferred amino acid compounds show a target to non-target ratio of at least 5:1, are stable in vivo and substantially localized to target within 1 hour after administration.
• Especially preferred amino acid compounds include [ 18 F]FAMP, ([ 18 F]5a) and [ 18 F]N-MeFAMP, ([ 18 F]5b).
• the invention features pharmaceutical compositions comprised of an ⁇ -amino acid moiety attached to either a four, five, or a six member carbon-chain ring.
• the invention features analogs of ⁇ -aminoisobutyric acid.
• the invention features amino acid compounds further comprising an imaging agent and uses for the compounds in detecting and/or monitoring tumors in a subject.
• the amino acid compound imaging agent is administered in vivo and monitored using a means appropriate for the label.
• Preferred methods for detecting and/or monitoring an amino acid compound imaging agent in vivo include Positron Emission Tomography (PET) and Single Photon Emission Computer Tomography (SPECT).
• Compounds of the invention include fluoro-, bromo- or iodo-substituted cyclobutyl, cyclopentyl, cyclohexyl amino acids, or singly unsaturated cyclic homologs thereof, or methylenyl fluoride or iodide-substituted analogs, or fluoro- or iodo-substituted isobutyl amino acids.
• the substituted compounds belong to the following generic formula:
• Ri is X, X HC: :CH- orR
• R 2 isH, orR 3 ifR 1 isR 3 .
• R4 is -(CkH 2 k + ⁇ ),-(CkH 2k - ⁇ ) or -(C k H 2k - 3 ) And where a is 1 to 5, xisOor 1, y is 1 or 2, z is 1, 2, 3 or 4 and z > y if y is 2, q is 1 or 0 if n is 1 and j is 0, n is 1 or 2, but 0 if m is 0, m is 0 or 1, j is 0 or 1, k is 1-5, and
• Non-cyclic, but sterically similar compounds of the invention have the following generic formula:
• Px4 is -(CkHac+i), -(C k H 2k - ⁇ ), or -(C k H 2k - 3 ), and R 2 is -(C k H 2k+1 ), -(CkHac-i), or -(C k H 2k - 3 ) k is 1-5.
• the compounds of the invention are useful as tumor-binding agents and as NMDA receptor-binding ligands, and in radio-isotopic form are especially useful as tracer compounds for tumor imaging techniques, including PET and SPECT imaging.
• X is At
• the compounds have utility for radio-therapy, since At isotopes are ⁇ -emitters.
• At isotopes are ⁇ -emitters.
• specialized, non-standard routes had to be devised, as described.
• the cyclic and non-cyclic compounds of the invention can be labeled with Technetium or Rhenium.
• Technetium-99m, Rhenium 186 and Rhenium 188 are known to be useful radionuclides for SPECT imaging.
• the cyclic and non-cyclic amino acids of the invention are joined to a Tc-99m or Rel 86 or Re 188 metal cluster through a 4-6 carbon chain which can be saturated or possess a double or triple bond.
• the Tc-99m metal cluster can be, for example, an alkylthiolato complex, a cytectrene or a hydrazino nicotinamide complex (FTYNIC), a cyclopentadienetricarbonyl or an N287 chelate.
• FTYNIC hydrazino nicotinamide complex
• the linking structure can be R 5 (replacing R3) in the foregoing diagram where R 5 is Z-(CH 2 ) a -CH b -CH, where a is 1, 2 or 3, b is 0, 1 or 2, and Z is an alkylthiolato-Tc or Re complex, a Tc- or Re-cytectrene or a Tc- or Re-FJYNIC complex or other Tc or Re chelate as known in the art.
• Tc of Tc 99m it will be understood to also illustrate an equivalent structure having Re 186 or Re 188 substituted for the Tc isotope.
• a is 1, 2 or 3 b is 0, 1 or 2 x is 0 or 1 y is 1 or 2 z is 1, 2, 3 or 4 and x>y if y is 2, q is 1 or 0
• R 4 is -(C H 2k+ ⁇ ),-(C k H 2 k- ⁇ ), or -(C H 2k - 3 ), where k is 1-5.
• Ri is Z
• a is 1 to 5
• R 4 is - (C k H 2 k+ ⁇ ), - (C k H 2k - ⁇ ), or - (C k H 2 k- 3 ), and
• R 2 is -(C k H 2k+ ⁇ ), -(C k H2k- ⁇ ), or -(C k H 2k . 3 ) k is 1-5.
• Z is
• Figs. 2A-2B are comparisons of activity in tumor tissue (Fig. 2A) and normal brain (Fig. 2B) after injection of [ 18 F]FAMP (5a) and [ 18 F]N-MeFAMP (5b). Tissues were compared at each time point by 2-tailed t-test. No significant differences in tumor uptake, but were detected. Bars indicate standard error.
• Compounds of the invention provide substantially improved PET and SPECT imaging for areas of the body having malignant tumors, especially tumors of the brain.
• the labeled compounds disclosed herein not only provide longer useful half-lives but also exhibit greater binding specificity for the target tissue/cells with low non-specific binding for the non-target tissues or cells.
• non-radioactive 5a and 5b are shown in Scheme 1.
• the aminonitrile 1 was prepared from fluoroacetone using a Strecker-type reaction.
• the carbamate 2 was prepared by treating the crude product of the acid hydrolysis of 1 with di-tert- butyl dicarbonate followed by flash chromatography.
• the amino acid 5a was obtained as its salt in analytically pure form by treating 2 with aqueous HC1.
• Compound 2 could also be obtained by treating 14a (see Scheme 4 for structure) with tetrabutylammonium fluoride and derivatizing the crude amino acid using di-tert-butyl dicarbonate.
• Preparation of 5b was performed starting with the carbamate 2.
• the ⁇ -methyl serine derivative 8 served as a common intermediate in the syntheses of [ 18 F]5a and [ 18 F]5b and was prepared as shown in Scheme 2.
• Alkaline hydrolysis of the hydantoin followed by treatment of the crude amino acid with di-tert-butyl dicarbonate gave the N-Boc acid 7.
• the t-butyl ester 8 was prepared from 7 using t-butyl-2,2,2-trichloracetimidate under neutral conditions [mony, J et al. (1998), Tetrahedron Lett. 39, 1557-1560].
• the aminoalcohol 12b was also prepared from compound 8.
• 8 was treated with methyl iodide and sodium hydride in DMF to afford the N-methyl derivative 10 in quantitative yield.
• Catalytic hydrogenolysis of 10 provided the alcohol 11, which was then converted to 12b with -toluenesulfonic acid as previously described.
• Scheme 4 depicts the formation of the cyclic sulfamidate precursors 14a and 14b and subsequent radiolabeling to produce the amino acids [ 18 F]5a and [ 18 F]5b.
• the aminoalcohols 12a and 12b were reacted with thionyl chloride in the presence of triethylamine to form cyclic sulfamidites 13a and 13b.
• Oxidation using sodium periodate with catalytic ruthenium (TV) oxide provided 14a and 14b from 13a and 13b, respectively.
• the precursors 14a and 14b are stable for at least 6 months when stored at -10°C.
• the radiolabeled amino acids were prepared in a one-pot synthesis by treating the precursor 14a or 14b with no-carrier-added [ 18 F]fluoride at 85°C for 20 minutes followed by acid hydrolysis at 85°C for 10 minutes. The reaction mixture was then passed through a column containing ion-retardation resin followed by alumina and C-18 SepPaks®. The eluted fractions were pH 6-7 and suitable for direct use in the rodent studies. In a representative synthesis, a total of 76 mCi of [ 18 F]5b at EOS was obtained from 166 mCi of 18 F (end of bombardment, EOB) in a synthesis time of approximately 90 minutes.
• the maximum amount of unlabeled material in the final product arising from the precursors is about 1 mg in each case.
• the minimum ratio of radiotracer to unlabeled material for both [ 18 F]5a and [ 18 F]5b is 1 mCi per 10 g of unlabeled material.
• This amount of unlabeled material is comparable to the amount present in doses of [ 18 F]FDG which also contain non-radioactive material arising from the triflate precursor of [ 18 F]FDG [Alexoff, DL et al. (1992), Internat. J. Rad. Appl.
• N-MeAIB is a selective competitive inhibitor of the A-type amino acid transport system while 2-amino- bicyclo[2.2.1]heptane-2-carboxylic acid (BCH) is commonly used as an inhibitor for the sodium-independent L-type transport system, although this compound also competitively inhibits amino acid uptake via the sodium-dependent B°' + and B° transport systems [Palacin, M et al. (1998), Physiol. Rev. 78: 969-1054].
• A- and L-type amino acid transport systems have been implicated in the in vivo uptake of radiolabeled amino acids used for tumor imaging [Jager, PL, et al. (2001), Nucl. Med., 42:432-445; Uehara, H et al. (1997), J. Cereb. Blood Flow Metab. 17:1239-1253].
• both [ 18 F]5a and [ 18 F]5b showed similar levels of uptake in 9L gliosarcoma cells, with intracellular accumulations of 0.43% and 0.50% of the initial dose per million cells after 30 minutes of incubation, respectively.
• the data were expressed as percent uptake relative to the control condition (no inhibitor) as shown in Figure 1.
• BCH blocked 48% of the uptake of activity relative to controls while N-MeAJJB blocked 80% of uptake relative to controls.
• [ 18 F]5a and [ 18 F]5b are substrates for the A-type amino acid transport system in 9L gliosarcoma cells based on the inhibition of uptake of both compounds in the presence of N-MeAIB.
• [ 18 F]5a is also a substrate in vitro for at least one non-A transport system, possibly system L, based on the inhibition of uptake by BCH.
• the data indicate that [ 18 F]5b is a more selective substrate for the A-type amino transport system than [ 18 F]5a, consistent with the increased selectivity of N-MeAIB for A-type transport relative to AIB [Shotwell, MA et al. (1983), Biochim. Biophys. Ada.
• the liver showed moderate uptake of activity, with 0.65% ID/g at 5 minutes which decreased to 0.48% ID/g after 120 minutes.
• the brain showed the lowest uptake of radioactivity, with approximately 0.05%) ID/g at all time points.
• tr ⁇ s * -[ 18 F]FACBC showed a 7:1 tumor to brain ratio with 1.72% ID/g in tumor tissue versus 0.26% ID/g in normal brain.
• a similar ratio of tumor to brain uptake of radiotracer was seen with tr ⁇ r ⁇ -[ 18 F]FACBC in a PET scan of a human volunteer with biopsy- confirmed glioblastoma multiforme (6:1 ratio at 20 minutes post-injection), suggesting that this rodent model is useful in predicting imaging properties of radiolabeled amino acids in human patients with brain tumors.
• the pancreas, kidneys and bladder would be predicted to bear the highest dosimetry burden in human studies employing [ 18 F]5a or [ 18 F]5b.
• the low uptake in other normal tissues suggests that both [ 18 F]5a and [ 18 F]5b might be suitable for imaging tumors exhibiting high uptake of these amino acids in locations other than the brain.
• the tumor to muscle ratios obtained at 60 minutes were 6.3:1 for [ 18 F]5a and 12:1 for [ 18 F]5b, while ratios of 5.3:1 for [ 18 F]FDG and 4.2:1 for tr r ⁇ -[ 18 F]FACBC were observed at this time point [Shoup, TM et al. (1999), J Nucl.
• FIG. 2 A A comparison of the uptake of radioactivity in tumor tissue and brain tissue after [ 18 F]5a and [ 18 F]5b administration is depicted in Figures 2 A and 2B.
• the higher ratios of tumor to brain uptake obtained with [ 18 F]5b versus [ 18 F]5a appear to be due to lower brain uptake of activity with [ 18 F]5b rather than higher tumor uptake of activity.
• No statistically significant differences were detected between the two compounds when comparing the uptake of activity in the tumor at the three time points studied (see Figure 2A). This observation is consistent with the amino acid uptake assay in which cultured 9L gliosarcoma cells accumulated [ 18 F]5a and [ 18 F]5b in similar amounts.
• the uptake of radioactivity in the normal brain tissue of rats receiving [ 18 F]5b was significantly less than in animals receiving [ 18 F]5a.
• the brain uptake was 0.054%) ID/g versus 0.022% ID/g in animals receiving [ 18 F]5b (p ⁇ .03 by a two-tailed t-test);
• the brain uptake was 0.050% ID/g versus 0.020%) ID/g in animals receiving [ 18 F]5b (pO.003 by a two-tailed t-test).
• the magnitude of the difference in brain uptake between the compounds is enough to account for the difference in tumor to brain uptake ratios at these time points. It is likely that the difference in normal brain uptake of activity is due to the higher selectivity of [ 18 F]5b versus [ 18 F]5a for the A-type amino acid transport system, which is not active at the normal BBB [Betz, AL et al. (1978), Science. 202:225-227]. Some of the other amino acid transport systems, such as the L-type transport system, are active at the normal BBB [Uehara, H et al. (1997), J Cereb. Blood Flow Metab. 17:1239-1253] and could potentially mediate uptake of these radiolabeled amino acids.
• the A-type amino acid transport system tolerates amino acid substrates with an N-methyl group while the other amino acid transport systems generally do not, [Palacin, M et al. (1998). Physiol. Rev. 78:969-1054; Shotwell, MA et al. (1983), Biochim. Biophys. Ada. 737:267-284; Christensen, HN et al. (1983) J. Med. Chem. 26:1374-1378] and the uptake inhibition assays discussed earlier suggest that [ 18 F]5b is a more selective substrate for A-type transport than [ 18 F]5a.
• both [ 18 F]FAMP (5a) and [ 18 F]NMeFAMP (5b) can be produced in high radiochemical yield (>78% EOB) and high radiochemical purity from stable precursors and are valuable agents for imaging brain tumors with PET.
• [ 18 F]5a provides an efficient route for preparing radiolabeled primary amines with 18 F in the ⁇ position.
• Uptake inhibition studies using 9L gliosarcoma cells demonstrated that both compounds are substrates for the A-type amino acid transport system, and these compounds represent the first report of 18 F-labeled amino acids that undergo significant uptake via A-type transport.
• Biodistribution studies with both compounds showed rapid and persistent accumulation of radioactivity in rodent brain tumors with an excellent signal to background ratio. Injection of [ 18 F]5b led to ratios of 104:1 and 97:1 in tumor versus normal brain at 60 and
• compounds of the invention can be labeled with an isotope of any atom or combination of atoms in the structure. While [ 18 F], [ 123 I]. [ 124 I], and [ 125 I] have been emphasized herein as being particularly useful for PET, SPECT, and tracer analysis, other uses are contemplated including those flowing from physiological or pharmacological properties of stable isotope homologs and will be apparent to those skilled in the art.
• At isotopes are emitters of alpha particles, where short range is useful for tumor radiotherapy.
• the invention also provides for technetium (Tc) labeling via Tc adducts.
• Isotope of Tc notably Tc 99m
• the present invention provides Tc-complexed adducts of compounds useful for tumor imaging.
• the adducts are Tc-coordination complexes joined to the cyclic and noncylcic amino acid by a 4-6 carbon chain which can be saturated or possess a double or triple bond. Where a double bond is present, either E (trans) or Z (cis) isomers can be synthesized, and either isomer can be employed. Synthesis can be carried out for incorporating the 99m Tc isotope as a last step, to maximize the useful life of the isotope.
• EXAMPLES technetium
• the phrase "usual work up” refers to the use of anhydrous magnesium sulfate followed by concentration under reduced pressure.
• the compounds 3-benzyloxypropanone [Boger, DL et al. (1992), J. Amer. Chem. Soc. 114:9318-9327] and bis(4-methoxyphenyl)chloromethane [Dutta, AK et al. (1996), J Med. Chem. 39:749-756] were prepared according to literature procedures.
• the target compounds 5a and 5b were prepared as racemic mixtures in both their fluorine- 18 and fluorine- 19 forms.
• Boc tert-butyl ester 4 (30 mg, 0.10 mmol) was stirred in 0.6 mL of 6 ⁇ HCl and heated to 70EC for 3 hours. The resulting solution was evaporated under reduced pressure, and the solid was washed with 2 X 10 mL of Et 2 O to provide 5b (16 mg, 91%) as a white solid: decomp 178- 181°C; 1H NMR (D 2 O) ⁇ 1.47-1.48 (3H, m), 2.73 (3H, s), 4.64-4.90 (2H, m). Anal. (C 5 HdonClFNO 2 ) C,H,N.
• reaction mix was partitioned between 10 mL of EtOAc and 10 mL of H O.
• the aqueous layer was further extracted with 3 X 10 mL of EtOAc.
• the organic layers were combined and washed with 20 mL of brine followed by usual work up.
• reaction mixture was diluted in 10 mL of EtOAc and washed with 10 mL of saturated NaHCO 3 solution.
• the aqueous layer was extracted with 2 X 10 mL of EtOAc, and the combined organic layers were washed with 10 mL brine followed by usual work up.
• the solvent was removed at 115EC with argon gas flow, and an additional 1 mL of CH 3 CN was added followed by evaporation with argon flow. This drying was repeated a total of 3 times to remove residual H 2 O.
• a 1-2 mg portion of the cyclic sulfamidate precursor 14a or 14b in 1 mL of dry CH3CN was added to the vial, and the reaction mix was heated at 85 °C for 20 minutes.
• the solvent was removed at 115°C with argon gas flow, and the intermediate product was treated with 0.5 mL of 6N HCl at 85°C for 10 minutes.
• the solution of radiolabeled amino acid was diluted in 1-2 mL of H 2 O and eluted in H 2 O through a 7 X 120 mm column of ion-retardation resin (Bio Rad AG11A8 50-100 mesh) in series with 2 Alumina N SepPaks ® and 1 C-18 SepPak®.
• the eluting fractions containing radioactivity were used directly in rodent studies.
• the isolated radiochemical yields were determined using a dose-calibrator (Capintec CRC-712M).
• the 9L gliosarcoma cells were initially grown as monolayers in T-flasks containing Dulbecco's Modified Eagle's Medium (DMEM) under humidified incubator conditions (37°C, 5% CO 2 /95% air).
• DMEM Dulbecco's Modified Eagle's Medium
• the growth media was supplemented with 10%) fetal calf serum and antibiotics (10,000 units/ml penicillin and 10 mg/ml streptomycin).
• the growth media was replaced three times per week, and the cells were passaged so the cells would reach confluency in a week's time.
• Rat 9L gliosarcoma cells were implanted into the brains of male Fischer rats as described previously [Shoup, TM et al. (1999), J. Nucl. Med. 40:331-338]. Briefly, anesthetized rats placed in a stereotactic head holder were injected with a suspension of 4 X 10 4 rat 9L gliosarcoma cells (1 X 10 7 per mL) in a location 3 mm right of midline and 1 mm anterior to the bregma at a depth of 5 mm deep to the outer table.
• IUCAC Institutional Animal Use and Care Committee
• Intracranial tumors developed that produced weight loss, apathy and hunched posture in the tumor-bearing rats, and the animals were used at 17-19 days after implantation. Of the 30 animals implanted with tumor cells, 25 developed tumors visible to the naked eye upon dissection and were used in the study.
• the tissue distribution of radioactivity was also determined in tumor-bearing Fischer 344 rats following intravenous injection of ⁇ 35 ⁇ Ci of [ 18 F]5a or [ 18 F]5b in 0.3 mL of sterile water.
• the procedure was similar to that already described for normal rats with the following modifications.
• the tail vein injections were performed in awake animals using a RTV-190 rodent restraint device (Braintree Scientific) to avoid mortality accompanying anesthesia in the presence of an intracranial mass.
• the animals were killed at 5 minutes, 60 minutes or 120 minutes post-injection.
• the same tissues were assayed as in normal rats with the addition of the tumor tissue, and the corresponding region of brain contralateral to the tumor was excised and used for comparison.
• the uptake in the tumor and contralateral brain at each time point was compared via a two-tailed t-test for paired observations (GraphPad Prism software package).

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• 2003
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