<p> This thesis describes the synthesis and characterization of a series of carborane
and metallocarborane-carbohydrate conjugates as model systems for developing a novel
class of radiophannaceuticals. The role of the carborane group is to provide a site for
binding radioactive elements while the carbohydrate moieties are present either as a
targeting vector, or as a means by which to increase the hydrophilicity of the overall
complex. In this research, the versatility of carboranes was demonstrated since it was
shown that carbohydrate-nido-carborane derivatives could be labeled with both metals
(Re/99Tc) and halogens (125I/127I). </p> <p> The initial synthetic target was compound 2.6, a simple nido-carboranyl glycoside
of glucose. The syntheses of this model ligand and its Re-metallocarborane (2.1, 3.4) and
iodinated (2.13) derivatives were carried out in order to determine the optimal methods
and conditions for synthesis and purification of bifunctional ligands and the
corresponding radioactive analogues. Microwave irradiation was found to greatly
enhance the synthesis ofRe and 99mTc-metallocarborane complexes which were isolated
in 31% and 58% yield respectively. Analysis of the Re complexes by 1H nOe NMR
spectroscopy revealed that rearrangement of the carborane cage from the expected 3,1 ,2-
ReC2B9 isomer to the 2,1 ,8- isomer occurred under the synthetic conditions employed. </p> <p> Iodination and radioiodination of model compound 2.6 was carried out using
Na[1271] or Na[125I] in the presence of Chloramine-T or Iodogen as oxidants at room
temperature. Reactions were complete in 5 min and the products isolated in 21% and
29% yield for 127I and 125I, respectively. </p> <p> Building on these results, bifunctional compounds 4.3 and 4.12 were prepared.
Using microwave heating, these compounds were labeled with 99mTc in 62% and 44%
yield, respectively. Compounds 4.3 and 4.12 contained a benzoic acid functionality
through which conjugation to targeting vectors could be accomplished. To demonstrate
this, benzamides 4.14 and 4.16 were synthesized using an active ester approach. The
products were isolated in 41% and 35% yield and subsequently labeled with 1251 using the
methods developed for the model system. Compounds [1251]-4.23 and [1251]-4.24 were
obtained in 73% and 92% yield, respectively. The stability of these [1251]-labeled
compounds was excellent, showing less than 1% degradation after 24 hours in solution.
In order to assess the effect of the carbohydrate moiety upon lipophilicity, the log P of the
radiolabeled benzamides was measured and found to be 1.53±0.01 for [125I]-4.23 and
0.82±0.04 for [1251]-4.24. This result confirmed the increase in hydrophilicity associated
with the presence of the carbohydrate moiety. </p> <p> Progress was also made towards preparing a glucose-nido-carborane conjugate
(5.9) whose Re and Tc complexes were pursued as metallocarborane analogues of the
clinical PET tracer [18F]FDG. The key precursor was made in good overall yield and the
product fully characterized. Future work should focus on preparing the radiolabeled
analogues. </p> / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/19800 |
| Date | 04 1900 |
| Creators | Green, Andrew |
| Contributors | Valliant, John, Chemistry |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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