Heart testing compound

The compound 15-(p-[.sup.125 I]-iodophenyl)-6-tellurapentadecanoic acid is disclosed as a myocardial imaging agent having rapid and pronounced uptake, prolonged myocardial retention, and low in vivo deiodination.

Radiohalogenated long-chain fatty acids have been evaluated heretofore for 
use in detecting changes in myocardial perfusion. The practical use of 
previously known compounds of this type for heart testing has been 
limited, however, because of their relatively short residence time in the 
myocardium and excessive accumulation in the blood of a subject tested 
therewith. In an article titled "Biochemical Concept and Synthesis of a 
Radioiodinated Phenylfatty Acid For In Vivo Metabolic Studies of the 
Myocardium", published in the European Journal of Nuclear Medicine, Volume 
15, 1980, H. J. Machulla et al reported that the use of radioiodinated 
15-(p-iodophenyl) pentadecanoic acid avoids the high concentration of 
radioactive iodide in the blood that is associated with the use of other 
radioiodinated long-chain fatty acids. It has been found, however, that 
washout of 15-(p-[.sup.125 I]iodophenyl) pentadecanoic acid from the 
myocardium is relatively rapid. In an article titled "Myocardial Imaging 
with 9-[Te-123m] Telluraheptadecanoic Acid", published in the Journal of 
Nuclear Medicine, Volume 22, Number 11, November 1981, Furn F. Knapp, Jr. 
et al reported that 9-[.sup.123m Te] telluraheptadecanoic acid shows rapid 
uptake and prolonged retention in the myocardium. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a new long-chain fatty acid 
compound for use in detecting and evaluating heart disease. 
Another object of this invention is to provide a long-chain fatty acid 
compound which combines the advantageous properties of 15-(p-iodophenyl) 
pentadecanoic acid and 9-[Te-123m] telluraheptadecanoic acid for use as a 
myocardial imaging agent, namely, the advantages provided by the 
radioactive iodine moiety of 15-(p-iodophenyl) pentadecanoic acid and the 
rapid uptake and prolonged retention in the myocardium exhibited by 
9-[Te-123m] telluraheptadecanoic acid. 
These objects are attained by the preparation of the new compound 
15-(p-[.sup.125 I]iodophenyl)-6-tellurapentadecanoic acid in accordance 
with techniques disclosed hereinafter.

DETAILED DESCRIPTION 
As will be described in detail hereinafter, the compound 15-(p-[.sup.125 
I]iodophenyl)-6-tellurapentadecanoic acid can be prepared by the steps 
represented in the following equations: 
##STR1## 
The following methods were employed in procedures reported herein. I-125 
was obtained commercially. All solvents and chemicals were analytical 
grade and were used without further purification. Melting points of 
compounds were determined in capillary tubes by using a Buchi SP 
apparatus. The petroleum ether used for elutions was analytical grade and 
had a boiling range of 30.degree.-60.degree. C. Thin-layer chromatographic 
analysis (TLC) was performed by using 250-.mu.m thick layers of silica gel 
G PF-254 coated on glass plates (obtained from Analtech, Inc.). Column 
chromatography was performed by using 60-200 mesh acidic or basic grade 
silicic acid (Sigma Chemical Co.). Infrared spectra (IR) were recorded on 
a Beckman 18-A spectrophotometer with NaCl plates or KBr pellets. 
Low-resolution mass spectra (MS) were recorded by using a Kratos MS-25 
low-resolution instrument under the following conditions: ionizing energy, 
70eV; accelerating potential, 8,000 V; trap current, 100 .mu.A; probe 
temperature, 200.degree.-300.degree. C. Proton nuclear magnetic Resonance 
spectra (.sup.1 H NMR) were obtained at 60 MHz with a Varian 360 -A 
instrument or at 200 MHz with a Nicolet high-resolution instrument. 
Samples (30-40 mg) were dissolved in deuteriochloroform (CDCl.sub.3), and 
resonances reported downfield from the internal tetramethylsilane 
standard. 
Step 1 illustrated above was conducted as follows: 
A mixture of 1-chloro-9-phenylnonane (1.19 g, 5 mmol), thallium (III) 
trifluoroacetate (2.72 g, 5 mmol), and trifluoroacetic acid (5 ml) was 
protected from light and stirred at room temperature for 16 hours. The 
resulting dark green solution was vacuum distilled (0.6 mm, bath 
temperature 40.degree. C.) followed by two vacuum codistillations with 
1,2-dichloroethane to remove the excess trifluoroacetic acid. The amber 
oil remaining in the distillation flask consisted of 3.12 g (90%) of the 
crude 1-chloro-9[p-[bis(trifluoroacetyl)thallium]-phenyl] nonane (compound 
1 above) which was used without further purification in the next step of 
the process. 
In step 2 the thallium intermediate 1(3.12 g, 4.5 mmol) was stirred in 
CH.sub.2 Cl.sub.2 (50 ml) at room temperature under red light with isoamyl 
nitrite (0.7 g, 6 mmol). A mixture of 12 N HCl (1.6 ml) and HOAc (2.4 ml) 
was then added and the solution was stirred 10 minutes. After the addition 
of 1.2 N HCl (20 ml), the solution was stirred an additional 10 minutes. 
The green mixture was washed several times with 0.1 N HCl and water and 
dried over anhydrous Na.sub.2 SO.sub.4, and CH.sub.2 Cl.sub.2 was removed 
in vacuo. The resulting green oil was chromatographed on a silicic acid 
(25 g). Fractions were eluted with petroleum ether (1-5) and 2% 
ether-petroleum ether (6-16 and 17-32). Fractions 17-32 were combined to 
give 0.83 g (70%) of 1-chloro-9-(p-nitrosophenyl) nonane (compound 2 
above) as a green oil. Analysis by TLC (2% ether-petroleum ether) 
indicated the presence of the single nonane component. 
In step 3 a mixture of the 1-chloro-9-(p-nitrosophenyl) nonane (1.0 g, 3.75 
mmol) and 10% palladium on charcoal (50 mg) was stirred in MeOH (5 ml) at 
room temperature under argon. Following the addition of NaBH.sub.4 (400 
mg, 10 mmol) in MeOH (5 ml), the mixture was stirred 30 minutes. The 
yellow solution was then filtered into H.sub.2 O (50 ml) and extracted 
with Et.sub.2 O. The combined Et.sub.2 O extracts were washed thoroughly 
with H.sub.2 O and dried over anhydrous Na.sub.2 SO.sub.4, and the solvent 
was removed in vacuo to yield 910 mg (97%) of the amine compound 3 (see 
step 3 above) as an orange oil (which was also analyzed by TLC). 
The amine intermediate compound 3 was stirred in step 4, with 0.5 N HCl (4 
ml) at 0.degree.-5.degree. C. Sodium nitrite (69 mg, 1 mmol) in H.sub.2 O 
(1 ml) was added dropwise to the mixture, which was then stirred at 
0.degree.-5.degree. C. for 5 minutes. Piperidine (403 mg, 4.5 mmol) in 
H.sub.2 O (3 ml) was then added dropwise while the temperature of the 
reaction mixture was maintained at 0.degree.-5.degree. C. The solution was 
stirred at 0.degree.-5.degree. C. for 30 minutes, poured into H.sub.2 O 
(50 ml), and extracted several times with CH.sub.2 Cl.sub.2. The combined 
organic extracts were washed thoroughly with H.sub.2 O and dried over 
anhydrous Na.sub.2 SO.sub.4, and the solvent was removed in vacuo. The 
crude product was dissolved in benzene (2 ml) and chromatographed on 
silicic acid (basic, 25 g) slurried in petroleum ether. Elution with 2% 
ether-ether petroleum gave 
1-[4-(9-chlorononyl)phenyl]-3,3-(1,5-pentanediyl) triazene (compound 4 
above) in fractions 8-13 (143 mg, 41%) as an orange oil, this compound 
being analyzed by TLC. 
In step 5, the triazene intermediate compound 4 (20 mg, 0.06 mmol) was 
dissolved in acetone (2 ml) and added dropwise to a mixture of 
triafluoroacetic acid (70 mg, 0.6 mmol) and sodium [.sup.125 I] iodide 
(4.68 mCi, 7.5 mg, 0.05 mmol) at 0.degree.-5.degree. C. The mixture was 
stirred at the same temperature for 5 minutes, diluted with H.sub.2 O, and 
extracted three times with ether. The combined ether extracts were washed 
thoroughly with H.sub.2 O, dried over anhydrous Na.sub.2 SO.sub.4, and the 
solvent removed under a stream of argon. The resulting oily residue was 
dissolved in 2 ml of petroleum ether and applied to a silicic acid column 
(acidic grade, 2 cm I.D.) in a petroleum ether slurry. Fractions 20 ml in 
volume were eluted with petroleum ether and aliquots were taken for 
counting and TLC analysis. Fractions 14-20 were combined to give 1.17 mCi 
(25%) of 1-chloro- 9 (p-[.sup.125 I] iodophenyl) nonane, compound 5 above. 
The produced showed a single radioactive component that co-chromatographed 
with unlabeled 1-chloro-9-(p-iodophenyl) nonane, R.sub.f 70 (2% 
ether-petroleum ether). 
The 1-chloro-9-(p-[.sup.125 I]iodophenyl) nonane was next reacted with 
sodium (methylvaleryl) tellurol, as shown in step 6 above. To obtain 
sodium (methylvaleryl) tellurol, Na.sub.2 Te.sub.2 (1.5 g, 5 mmol) was 
reacted with Br-(CH.sub.2).sub.4 -COOCH.sub.3 (2.15 g, 11 mmol) to provide 
bis-(methylvaleryl) ditelluride, and the orange-colored ditelluride (48 
mg, 0.1 mmol) was then reduced under argon at room temperature with excess 
NaBH.sub.4 in ethanol (10 mL) to the colorless solution of the sodium 
(methylvaleryl) tellurol compound 6 above. As illustrated in the equation 
representing step 6 above, a solution of 1-chloro-9(p-[.sup.125 
I]iodophenyl) nonane (4.6 mg) in 5 ml of ethanol was added dropwise to 5 
ml of the solution of sodium (methlyvaleryl) tellurol prepared as 
indicated above. The resulting mixture was refluxed under argon for 1 
hour, cooled in an ice bath, diluted with H.sub.2 O, and extracted three 
times with ether. The ether extracts were washed with H.sub.2 O, dried, 
and the solvent was removed in the usual manner. The product was 
chromatographed on a silicic acid column (basic grade, 2 cm I.D.). 
Fractions 24-27 were combined to give 1.1 mCi (80%) of 
methyl-15(p-[.sup.125 I]iodophenyl)-6-tellurapentadecanoate) compound 7 
above. Upon TLC analysis, the produced showed a single radioactive 
component that co-chromatographed in C.sub.6 H.sub.6 with unlabelled 
methyl-15(p-iodophenyl)-6-tellurapentadecanoate. 
In step 7, the estermethyl-15(p-[.sup.125 
I]iodophenyl)-6-tellurapentadecanoate (5.7 ml) was refluxed under argon 
for 30 minutes in ethanol (6 ml) containing 2 ml of 1 N NaOH (2 mmol). 
After cooling, the solution was diluted with H.sub.2 O, the pH adjusted to 
2-4 with 10% H.sub.2 SO.sub.4, and the resulting cloudy solution extracted 
several times with ether. After washing with H.sub.2 O and drying over 
anhydrous Na.sub.2 SO.sub.4, the solvent was evaporated under argon to 
give 715 .mu.mCi (65%) of 15-(p-[.sup.125 
I]-iodophenyl)-6-tellurapentadecanoic acid, which showed a single 
radioactive component (R.sub.f 0.50) on TLC analysis (8% MeOH/CHCl.sub.3). 
The specific activity of the product was 94 mCi/mmol. 
The intermediate compound 1-chloro-9(p-iodophenyl) nonane (compound 5 
above) was also prepared as follows. To a solution of 1-chloro-9[p[bis 
(trifluoroacetyl)thallium]phenyl]nonane (2.04 g, 3 mmol) in H.sub.2 O (30 
mL) was added potassium iodide 3.00 g, 17 mmol), and the resulting cloudy 
solution was stirred at room temperature for 15 minutes. Sodium 
metabisulfite (1 g) was then added, and the mixture was stirred until the 
solution turned yellow. After being stirred 30 minutes, the solution was 
made basic with 1 N NaOH, filtered, and extracted thoroughly with ether. 
The combined ether extracts were washed with H.sub.2 O, dried over 
anhydrous Na.sub.2 SO.sub.4, and evaporated in vacuo to afford a yellow 
residue. The residue was taken up in benzene (2 ml) and chromatographed to 
yield 0.64 g (64%) of 1-chloro-9(p-iodophenyl)nonane, compound 8 above. 
In Table I, the tissue distribution of radioactivity in rats after 
intravenous administration of a bovine serium-albumin complex of the 
15-(p-[.sup.125 I]-iodophenyl)-6-Tellurapentadecanoic acid is summarized 
for various time periods from 5 minutes to 5 days. For comparison, the 
data for percent injected dose/organ are shown in Table II. 
TABLE I 
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DISTRIBUTION OF RADIOACTIVITY (% INJECTED DOSE/G OF TISSUE) 
IN RAT AT VARIOUS TIMES AFTER INTRAVENOUS ADMINISTRATION OF 
15-(p-[.sup.125 I]IODOPHENYL)-6-TELLURAPENTADECANOIC ACID* 
Time after Injection: Percent injected dose/g (range) 
Tissue 
5 min 30 min 
60 min 
2 h 6 h 1 d 5 d 
__________________________________________________________________________ 
Heart 
5.87 5.43 5.55 5.85 4.78 3.25 0.94 
(5.30-6.45) 
(4.35-5.98) 
(4.01-7.27) 
(4.01-7.56) 
(3.89-5.33) 
(3.02-3.41) 
(0.77-1.13) 
Blood 
0.26 0.45 0.34 0.42 0.31 0.20 0.03 
(0.24-0.27) 
(0.38-0.50) 
(0.28-0.40) 
(0.32-0.57) 
(0.29-0.32) 
(0.18-0.21) 
(0.03-0.034) 
Lungs 
1.14 1.25 1.48 1.57 1.10 0.89 0.33 
(0.86-1.52) 
(1.14-1.40) 
(1.10-1.95) 
(1.29-2.05) 
(0.97-1.17) 
(0.77-1.05) 
(0.30-0.36) 
Liver 
9.57 7.78 7.69 8.38 8.37 6.24 1.28 
(8.97-10.28) 
(6.73-8.86) 
(6.68-8.28) 
(7.32-9.90) 
(7.86-9.08) 
(5.53-6.73) 
(1.23-1.36) 
Kidneys 
1.02 1.25 1.41 1.37 1.12 0.70 0.20 
(0.79-1.15) 
(1.09-1.39) 
(1.23-1.55) 
(1.20-1.69) 
(0.95-1.20) 
(0.63-0.80) 
(0.18-0.22) 
Thyroid 
1.52 1.51 1.48 3.51 5.89 22.78 30.25 
(1.41-1.63) 
(0.83-2.21) 
(0.95-1.94) 
(1.91-4.42) 
(5.33-7.08) 
(18.15-27.13) 
(25.26-34.81) 
__________________________________________________________________________ 
TABLE II 
__________________________________________________________________________ 
DISTRIBUTION OF RADIOACTIVITY (% INJECTED DOSE/ORGAN) OF 
RADIOACTIVITY IN RAT AT VARIOUS TIMES AFTER INTRAVENOUS ADMINISTRATION 
OF 15-(p-[.sup.125 I]IODOPHENYL)-6-TELLURAPENTADECANOIC ACID* 
Time after Injection: Percent injected dose/organ (range) 
Tissue 
5 min 30 min 60 min 2 h 6 h 1 d 5 d 
__________________________________________________________________________ 
Heart 2.98 2.61 2.87 2.87 2.32 1.60 0.45 
(2.80-3.35) 
(2.19-2.91) 
(2.09-3.80) 
(2.60-3.48) 
(1.66-2.65) 
(1.40-1.73) 
(0.38-0.52) 
Blood 2.00 3.41 2.66 3.01 2.26 1.50 0.23 
(1.89-2.09) 
(2.65-3.93) 
(2.24-3.24) 
(2.33-3.99) 
(2.23-2.31) 
(1.37-1.62) 
(0.22-0.25) 
Lungs 0.97 1.05 1.01 1.29 0.85 0.70 0.24 
(0.74-1.30) 
(0.97-1.04) 
(0.85-1.16) 
(1.12-1.67) 
(0.73-0.94) 
(0.58-0.85) 
(0.22-0.26) 
Liver 50.94 39.28 39.03 44.03 46.39 34.28 6.46 
(46.13-55.20) 
(34.11-43.16) 
(34.62-41.81) 
(41.59-47.61) 
(43.86-49.26) 
(32.02-37.42) 
(6.00-6.84) 
Kidneys 
1.25 1.52 1.73 1.53 1.25 0.81 0.23 
(0.95-1.44) 
(1.42-1.63) 
(1.47-1.97) 
(1.37-1.80) 
(1.09-1.38) 
(0.74-0.87) 
(0.21-0.27) 
Thyroid 
0.02 0.02 0.02 0.04 0.07 0.26 0.32 
(0.02-0.02) 
(0.01-0.02) 
(0.01-0.02) 
(0.02- 0.05) 
(0.06-0.09) 
(0.22-0.30) 
(0.28-0.35) 
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The rapid and pronounced myocardial uptake observed with the disclosed 
imaging agent in analogous to that reported for 9-[.sup.123m Te]-HDA. 
Prolonged retention of radioactivity is exhibited by the 15-(p-[.sup.125 
I]iodophenyl)-6-tellurapentadecanoic acid, and studies have indicated that 
its p-iodophenyl moiety does not interefere with the myocardial 
specificity observed with similar agents. After 6 hours the heart retained 
80% of the maximum uptake observed after 5 minutes (Table I). The 
radioactivity in the heart retained 55% of the maximal value after 24 
hours. The mean heart-to-blood ratios were 22:1 at 5 minutes and 17:1 at 2 
hours. Only marginal radioactivity accumulated in the thyroid tissue; 
1.52% dose/g after 5 minutes and 5.84% dose/g after 6 hours. The minimal 
thyroid radioactivity (Table I) and low blood levels demonstrate that the 
attachment of the radioiodine to the phenyl ring is an effective means of 
stabilizing the iodine and overcoming facile in vivo cleavage. 
The rats used in the study were housed in metabolism cages and liquid and 
solid wastes were collected daily after injection of 15-(p-[.sup.125 
I]-iodophenyl)-6-tellurapentadecanoic acid to determine the biological 
half-life of this new agent and its relative excretion in urine and feces. 
These studies were conducted over a five-day period, which represents a 
decay period of half-lives for 13.2-hr iodine-123. The cumulative 
excretion levels in urine and feces were 43.2.+-.1.8% injected dose after 
two days and 71.6.+-.8.3% after five days. The radioactive content of the 
urine (20.8.+-.2.1%) and feces 22.4.+-.1.1%) were similar after two days, 
but after five days the cumulative fecal activity (41.4.+-.4.3%) was 
greater than that for urine (30.5.+-.4.0%). The pronounced heart uptake, 
minimal deiodination, rapid blood clearance, and prolonged myocardial 
retention of 15-(p-[.sup.125 I]iodophenyl)-6-tellurapentadecanoic acid 
suggest that the .sup.123 I-labeled analog is also an attractive agent 
with which to evaluate myocardial perfusion.